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Iqbal, H. M. N., Kyazze, G., and Keshavarz, T. (2013). "Advances in the valorization of lignocellulosic materials by biotechnology: An overview," BioRes. 8(2), 3157-3176.

Abstract

In view of the worldwide economic and environmental issues associated with the extensive use of petro-chemicals, there has been increasing research interest during the past decade in the value of residual biomass. Because of its renewable nature and abundant availability, residual biomass has attracted considerable attention as an alternate feedstock and potential energy source. To expand the range of natural bio-resources, significant progress related to the lignocellulose bio-technology has been achieved, and researchers have been re-directing their interests to biomass-based fuels, ligninolytic enzymes, chemicals, and biocompatible materials, which can be obtained from a variety of lignocellulosic waste materials. This review article focuses on the potential applications of lignocellulosic materials in biotechnology, including the production of bio-fuels, enzymes, chemicals, the pulp and paper, animal feed, and composites.


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Advances in the Valorization of Lignocellulosic Materials by Biotechnology: An Overview

Hafiz Muhammad Nasir Iqbal,* Godfrey Kyazze, and Tajalli Keshavarz

In view of the worldwide economic and environmental issues associated with the extensive use of petro-chemicals, there has been increasing research interest during the past decade in the value of residual biomass. Because of its renewable nature and abundant availability, residual biomass has attracted considerable attention as an alternate feedstock and potential energy source. To expand the range of natural bio-resources, significant progress related to the lignocellulose bio-technology has been achieved, and researchers have been re-directing their interests to biomass-based fuels, ligninolytic enzymes, chemicals, and biocompatible materials, which can be obtained from a variety of lignocellulosic waste materials. This review article focuses on the potential applications of lignocellulosic materials in biotechnology, including the production of bio-fuels, enzymes, chemicals, the pulp and paper, animal feed, and composites.

Keywords: Lignicellulosic Material; Green Chemistry; Applications; Lignocellulose Biotechnology

Contact information: Applied Biotechnology Research Group, School of Life Sciences, University of Westminster, 115 New Cavendish Street, London W1W 6UW, UK;

* Corresponding author: E-mail: hafiz.iqbal@my.westminster.ac.uk

INTRODUCTION

Lignocellulosic materials may be described as one of the most promising natural, abundant, and renewable feedstock available for the enhancement and maintenance of industrial societies and critical to the development of a sustainable global economy (Kumar et al. 2009). Large amounts of lignocellulosic materials are generated through agricultural practices mainly from timber operations, pulp and paper manufacture, and many agro-based processes (Pérez et al. 2002). Today, lignocellulosic materials have gained a special importance for product development because of their renewable nature (Asgher et al. 2013). Their physical and chemical characteristics give them great potential for biotechnical applications (Malherbe and Cloete 2002). Regrettably, many lignocellulosic materials are still often disposed of by burning, a practice that is not restricted to developing countries alone, but can be considered a global problem. However, the huge amounts of lignocellulosic biomass that are available on the planet can potentially be converted into a variety of different value-added products (Hu et al. 2008; Lucia 2008; Isroi et al. 2011) (Fig. 1), including bio-fuels, cheap energy sources for microbial fermentation and their enzyme production, chemicals, pulp and paper production, improved animal feedstuffs, and polymer composites for materials science.

Fig. 1. Options for bio-conversion of biomass into value-added bio-products

Composition of Lignocellulosic Materials

The major structural components of woody plants, as well as grasses and agricultural residues, are lignin, hemicellulose, and cellulose. Most agricultural lignocel-lulosic biomass is comprised of 10% to 25% lignin, 20% to 30% hemicellulose, and 40% to 50% cellulose (Pérez et al. 2002; Kumar et al. 2009).

Lignin can be regarded as a complex polymer comprised of variously linked aromatic alcohols (coniferyl alcohol, sinapyl alcohol, and p-coumaryl alcohol) (Fig. 2), and is further linked to both hemicelluloses and cellulose, forming a physical seal around the latter two components (Pérez et al. 2002; Sánchez 2009; Calvo‐Flores and Dobado 2010; Jiang et al. 2010).

Hemicellulose macromolecules are often repeat polymers of pentoses, hexoses, and a number of sugar acids. Depending on the source, the hemicelluloses are highly branched with a lower degree of polymerization than cellulose, and they vary in the structural composition due to the genetic variability among different sources. However, most of the lignocellulosic materials have similar properties even though they may differ in the chemical composition and the matrix morphology.

Cellulose is a homogenous linear polymer of D-glucopyranose sugar units (Sánchez 2009; Kumar et al. 2009; Bertero et al. 2012), that are linked in a β configuration (Fig. 2). The average cellulose chain has a degree of polymerization of about 9,000 to 10,000 units. About 65 percent or more of the cellulose is highly oriented, crystalline, and not accessible to water or other solvents. The cellulose is further protected from degradation because of its close association to a sheath of matrix polymers that include lignin and hemicelluloses. Table 1 shows the typical chemical compositions of all of these three components in various lignocellulosic materials that vary in their composition due to the genetic variability among different sources (Malherbe and Cloete 2002; McKendry 2002; John et al. 2006; Prassad et al. 2007; Kumar et al. 2009; Sánchez, 2009; Bertero et al. 2012).

Fig. 2. Chemical structure of lignocellulosic material; (A) Building blocks/units of Lignin; (B) Xylose unit of hemicellulose; and (C) Cellulose

Table 1. Percent Composition of Lignocellulose Components in Various Lignocellulosic Materials

Potential Applications of Lignocellulosic Materials

From a biotechnological point of view, a wide variety of lignocellulosic resources are available for conversion into value-added bio-products. During the last several years, considerable improvement in processes related to lignocellulose biotechnology has been achieved. In addition to the growing concerns for traditional applications (bio-fuels, enzymes, chemicals, pulp and paper, animal feedstuff, composites, etc.), novel markets for lignocellulosics have been identified in recent years. The most ambitious of these has been the conversion of lignocellulose to alternative energy carriers, e.g. fuel ethanol (Shuit et al. 2009; Sakamoto et al. 2012; Asgher et al. 2013; Shahsavarani et al. 2013). The pulp and paper industry has discovered that lignocellulose biotechnology can improve process efficiency, yielding savings in money and energy. Defeating the lignin barriers, which prevent commercial exploitation of lignocellulose, will be the key to its successful application in biotechnological endeavors. As indicated in the descriptions that follow, some of this research has focused on potential applications in the industrial sector of the modern era of bio-technology. This article focuses on an area that has not been comprehensively reviewed – potential applications of lignocellulosic materials in bio-technology, mainly including the production of bio-fuels, enzymes, chemicals, the pulp and paper, animal feedstuff, and composites.

Bio-fuel

Increasing costs of fossil fuels and their greenhouse gas effects are creating an urgent need to explore alternative cheaper and environment friendly bio-fuel resources as a strategy for reducing global warming. Air pollution, global warming, and the future of oil production are among the major causes of public and private interest in developing ethanol as an additive alternative or substitute for fossil fuel oil. Currently, bio-ethanol is produced on an industrial scale from sucrose and starch-based grains (Reijnders and Huijbregts 2007; Asgher et al. 2013). However, to avoid direct competition between fuel ethanol and food production, the feedstocks for bio-ethanol production ideally should be derived from inedible parts of food crops (Mathews 2007; Goldemberg et al. 2008; Andrade de Sá et al. 2011; Gnansounou 2011).

One potential approach for the low-cost fermentative production of ethanol is to utilize agro-industrial residual materials. The carbohydrates present in such biomass must be first converted into simple sugars (especially glucose), which then can be fermented into ethanol, a potential fuel for transportation (Lin and Tanaka 2006; Alonso et al. 2008; Balat and Balat 2009). The leading nations in the production of bio-ethanol are Brazil and the USA (Aalam et al. 2007). Asian countries altogether account for about 14% of the world’s bio-ethanol production. Research has shown that ethanol can be produced using raw materials from sugar cane bagasse, maize cobs, coconut husks (copra), groundnut, other nut shells, sawdust, cereal straw corn stover, rice straw, and rice husks (Chandra et al. 2007; Yang and Wyman 2008, Shuit et al. 2009; Sukumaran et al. 2009; Sakamoto et al. 2012; Asgher et al. 2013; Shahsavarani et al. 2013). Such transformation of biological resources, including energy-rich crops or forestry residuals requires pre-treatment of the feedstock to allow more rapid enzymatic conversion into sugar, i.e. saccharification (Cardona and Sánchez 2007). Fermenting organisms then convert the sugar into ethanol. Pre-treatment of these lignocellulosic biomass-based materials release sugars and, most importantly, glucose for the fermentation into ethanol.

Many different pre-treatment methods have been reported, including biological, chemical, physical, thermal, and enzymatic approaches (Chandra et al. 2007; Yang and Wyman 2008, Yang et al. 2011; Asgher et al. 2013; Hamzeh et al. 2013; Rohowsky et al. 2013). Bio-delignification is useful in the pre-treatment, and it replaces or supplements the chemical-based pre-treatments, which include mechanical treatment with acid, alkali, and steam explosion. Recent advances in the characterization of ligninolytic enzymes involving the degradation of lignin have given new impetus to the research in this area, which has now become amenable to biotechnological exploitation (Asgher et al. 2012a,b,c; Pal et al. 2013). Bio-conversions of lignocellulosic materials to useful products normally require multi-step processes that include pre-treatment, enzymatic hydrolysis, and fermentation (Fig. 3).

Fig. 3. Generalized schematic representation of lignocellulosic materials bio-conversion into ethanol

Production of Enzymes

Enzyme production is a growing field of biotechnology and has become a central part of the modern biotechnology industry. One of the most appropriate approaches to produce low cost and efficient enzymes for biotechnological application purposes is to utilize the potential of lignocellulosic waste materials. Some such mixtures may contain significant concentrations of soluble carbohydrates and inducers of enzyme synthesis so as to allow efficient production of ligninolytic enzymes (Reddy et al. 2003, Moldes et al. 2004; Elisashvili et al. 2006; Iqbal et al. 2011a,b; Asgher and Iqbal 2011; Asgher et al. 2012c). To date, the production of various ligninolytic enzymes including lignin peroxi-dase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccases, and other lignocellulytic enzymes, mainly cellulases, have been widely studied in submerged and solid culture processes in the laboratory, ranging from shake flask to a large scale (Xia and Len 1999; Moldes et al. 2004; Elisashvili et al. 2006). Due to the lower capital investment and operating costs of solid state fermentation (SSF), that approach has been reported as an attractive alternative process to produce fungal microbial enzymes using different agro-industrial based lignocellulosic materials (Jecu 2000; Couto and Sanromán 2005; Couto and Sanromán 2006; Levin et al. 2008; Oberoi et al. 2010; Iqbal et al. 2011a,b).

A wide spectrum of lignocellulosic materials has gained special attention from both the academic and industrial researchers because of their potential as inexpensive carbon and energy sources for the production of ligninolytic and lignocellulolytic enzymes. A miscellaneous spectrum of lignocellulolytic or lignin-degrading micro-organisms, mainly white rot fungi (Baldrian and Gabriel, 2003; Ander and Eriksson 2006; Asgher et al. 2008; Sánchez, 2009; Alvira et al. 2010; Asgher et al. 2012a,b,c; Asgher and Iqbal 2013; Iqbal and Asgher 2013), have been isolated and identified in recent years, and this list still continues to grow rapidly. The white-rot fungi belonging to the basidiomycetes are the most efficient and extensive lignin degraders (Asgher et al. 2008; Irshad et al. 2012), with P. chrysosporium being regarded as the model culture and best-studied lignin-degrading fungus, producing copious amounts of a unique set of lignocellulytic enzymes. Enzymes denoted by LiP, E.C. 1.11.1.14, MnP, E.C. 1.11.1.13, and laccase E.C. 1.10.3.2 are the major types secreted by white-rot fungi during the degradation of lignin in the lignocellulosic substrates (Bandounas et al. 2011; Asgher et al. 2011; Asgher et al. 2012a). Phanerochaete chrysosporium has drawn considerable attention as an appropriate host for the production of lignin-degrading enzymes or for direct application in the lignocellulose bioconversion processes (Bosco et al. 1999; Ruggeri and Sassi 2003). Ligninolytic enzymes, cellulases, and hemicellulases are important industrial enzymes having numerous applications and the biotechnological potential for various industries including chemicals, fuel, food, brewery and wine, animal feed, textile and laundry, pulp and paper, and agriculture (Bhat 2000; Jecu 2000; Beauchemin et al. 2003; Couto and Sanromán 2005; Couto and Sanromán 2006; Eun et al. 2006; Papinutti and Forchiassin 2007; Papinutti and Lechner 2008; Levin et al. 2008; Oberoi et al. 2010; Stoilova et al. 2010; Asgher et al. 2011; Asgher and Iqbal 2011; Iqbal et al. 2011a; Yoon et al. 2012; Asgher and Iqbal 2013; Iqbal and Asgher 2013; Irshad et al. 2013). A range of different lignocellulosic materials that have successfully been adopted for the production of different enzymes having industrial importance are summarized in Table 2.

Chemicals Production

Lignocellulosic materials are renewable resources that can be directly or indirectly used for the production of many useful biological and chemical products (Ghosh and Singh 1993; Moldes et al. 2007; Sarrouh et al. 2009; Chandel et al. 2011; Kamat et al. 2012; Misra et al. 2013). Production of such chemicals could significantly improve the economics of a bio-refinery. The introduction of a bio-refinery approach to produce bio-chemicals from renewable raw materials is one potential opportunity to cover the increased demand for fine chemicals and consequently reduce the fossil dependence of the petro-chemicals. The goal of the bio-refinery approach is the generation of energy and chemicals from different biomass feedstocks, through the combination of different treatment technologies (Fitz-Patrick et al. 2010). In the last several years, some studies have revealed the potential of lignocelluloses for bio-refinery purposes (Cherubini 2010). A simple lignocellulose bio-refinery scheme involves a single or multi-step pre-treatment (physical, chemical, or biological) of biomass to initially separate fractions of different lignocellulosic biomass components (cellulose, hemi-cellulose, and lignin). Figure 4 displays a simple integrated lignocellulose bio-refinery scheme for the production of various value-added bio-chemical products. In this context, extensive research has been undertaken for the bio-conversion of lignocellulosic materials, and hydrolysate-derived carbohydrates, into several value-added products and renewable bio-chemicals (Chandel and Singh 2011).

A range of products such as glucose (mainly from cellulose and hemicellulose), xylose, mannose, galactose, and acetic acid (from hemicellulose), and phenolic compounds (from lignin) are produced during the hydrolysis process. Many authors have investigated the polymeric fractionation of the hemicellulose portion of agricultural residues such as corn stover, rice straw, sugarcane bagasse, eucalyptus, spent grain, and corncob to obtain a variety of marketable and renewable bio-chemicals, including xylitol, phenols, guaiacols, catechols, vanillin, vanillic acid, syringaldehyde, benzene, biphenyls, and cyclohexane from lignocellulosic biomass (Canilha et al. 2004; Carvalho et al. 2005; Deng et al. 2006; Moldes et al. 2007; Kumar et al. 2008; West 2009; Gandini, 2011; Ji et al. 2012; Reichert et al. 2012; Varanasi et al. 2013).

Fig. 4. Generalized scheme of integrated lignocellulose bio-refinery for the production of various value-added bio-chemical products

Table 2. List of Various Lignocellulosic Materials Used for the Production of Different Microbial Enzymes

Xylitol has been identified as one of the most valuable chemicals derived from agro-residual lignocellulosic biomass (Kumar et al.2008). Because of its proven marketable applications in food and pharmacological industries, it is an attractive candidate for its low-cost production using lignocellulosic materials (Misra et al. 2013). The hemicellulosic fraction of waste materials, such as sugar industry wastes (sugar cane bagasse), provides an important source of xylose that can be converted to xylitol by microbial fermentation (Sarrouh et al. 2009; Chandel et al. 2011). In this regard, several researchers have explored an alternative route, wherein the selection of naturally occurring xylose-fermenting microorganisms i.e., bacteria, yeasts, and fungi capable of producing xylitol from agro-industrial lignocellulosic residues is emerging as a promising approach (Ji et al. 2012; Kamat et al. 2012; Misra et al. 2013).

The major bottleneck against comprehensive applications of lignocellulosic biomass as raw material to obtain bio-chemicals is the lack of technology for the efficient conversion of biomass into various value-added bio-chemicals. However, there are certain other drawbacks and limitations in using different pre-treatments methods. These include high costs of alkaline/acids catalyst and the need for recovery, high costs of corrosive resistant equipment, partial degradation of hemicellulosic components during the process, and the generation of inhibitory/toxic compounds. The limiting factor is simply that low cost processing technologies to efficiently convert a large fraction of the lignocellulosic biomass into bio-chemicals do not yet exist. In this regard, extensive research is needed in order to develop a comprehensive understanding of the fundamental chemistry, science, and engineering underpinning the transformation of lignocellulosic materials into value-added products.

Pulp and Paper Industry

Paper is a ubiquitous product used for many applications in our daily lives (Manda et al. 2012). The pulp and paper industry processes huge quantities of lignocel-lulosic materials. In addition to direct harvesting of wood, straw, and bamboo, etc., the industry also uses residual materials from other manufacturing processes (wood chips from sawmills, bagasse from sugarcane processing, etc.), or fibers recovered from recycled paper or paperboard (Gupta 2007). With an increasing demand for paper, and with improvements in pulp processing technology (Singh et al. 2012), pulp and paper can be made from different lignocellulosic materials, and three major processing steps are involved, i.e. (i) pulping, (ii) bleaching, and finally (iii) paper production (Habibi et al. 2008; Singh et al. 2010). There are three main types of pulping, i.e. (i) mechanical pulping, (ii) chemical pulping, and lastly (iii) chemi-mechanical pulping (combination pulping). The mechanical pulping mainly involves the grinding of raw material (usually a lignocellulosic material) to separate the fibres without significant dissolution of lignin (Havimo and Hari 2010). Chemical pulping typically involves use of alkaline chemicals at high temperatures to remove much of the lignin and to separate the fibres. In comparison to mechanical pulping, the chemical pulping process uses less energy and produces a lower fibre yield, typically ranging from 50 to 60% (Messner et al. 1998; Bajpai 1999; Bajpai et al. 2003) with a superior paper quality. On the other hand, it produces concentrated liquid effluents, some components of which are toxic, mutagenic, persistent, bio-accumulating, and cause numerous harmful disturbances in biological systems (Bajpai 1999). A large amount of energy and water is required for the entire processes of the pulp and paper industry (Pokhrel and Viraraghavan 2004). Because of the high chemical consumption, chemical pulping also poses some serious effects to the environmental ecosystem. As an alternative to the existing chemical-based pre-treatment technologies, which are usually hazardous to health, expensive, commercially and environmentally unattractive, biological pre-treatment or bio-pulping offers an alternative cost-effective, low chemical demanding, and eco-friendly approach to overcome some of the challenges inherent in the manufacture of pulp and paper. Recent reports show that a biological-based approach has potential for improving both the economics and the environmental impact of the pulp generation. Bio-pulping can be defined as the biological pre-treatment using white rot fungus to metabolize the lignin in wood, freeing up the fibers so that they can be used for paper production (Rademacher 2004; Habibi et al. 2008; Tuncer et al. 2009; Singh et al. 2010; Fu et al. 2012) (Fig. 5). Bio-pulping by the introduction of certain lignocellulytic enzymes at different stages of pulp manufacturing prior to bio-bleaching allows substantial savings of electrical power and it decreases pollutants (Singh et al.2010; Singh et al. 2012; Saritha and Arora 2012).

Fig. 5. Scheme of integrated bio-processing of lignocellulosic materials for the production of bio-pulp and animal feedstuff

Animal Feed Production

Cellulose is the most important carbon and energy source in a ruminant’s diet. The concept of preferential delignification of lignocellulose materials by white-rot fungi has been applied to increase the nutritional value (Chen and Dixon 2007; Chen et al.2010). The white-rot fungi degrade lignin and improve the in-vivodry matter digestibility of lignocellulosic materials (Cohen et al. 2002; Phan and Sabaratnam 2012; Saritha and Arora 2012). This increased digestibility provides organic carbon that can be fermented to organic acids in an anaerobic environment, such as the rumen. Most of the lignocel-lulosic agricultural residues are enriched in microbial protein, enzymes, and bio-factors that can be used as animal feedstuff directly or after partial treatments (Isikhuemhen et al. 1996; Nigam, and Singh 1996; Huettermann et al. 2000) (Fig. 5). A more promising avenue is the supplementation of animal rations with feed enzymes produced by solid-state fermentation using many other cellulosic-based materials (Pluske and Lindemann 2000). For instance, in the integrated bio-processing of sweet sorghum, the extracted partially digested and enzyme enriched pulp is a valuable feed ingredient in animal feed rations (Tengerdy et al. 1996). According to the investigations of Adamović et al. (1998), the most notable change of composition in spent straw substrate is the reduction of hemicelluloses by 17%, cellulose by 15%, lignin by 4%, and gossypol by 60% (Zhu et al.2012). Recent studies have proved that some polysaccharides, vitamins, and trace elements such as Fe, Ca, Zn, and Mg, are valuable components and play an important role for animals in the digestibility of feedstuffs (Medina et al. 2009; Paredes et al. 2009; Zhu et al. 2012).

Composites Production

In recent years, a great deal of research effort has been directed towards the use of lignocellulosic waste residual materials in the place of synthetic materials to prepare various composites with different functionalities of interest. For this reason, the development of bio-based composites has been a subject of interest in materials science from both ecological and environmental perspectives (Bajpai et al. 2013). Among the possible alternatives, the development of composites using lignocellulosic materials as reinforcing fillers for thermo-plastic polymers is currently receiving increasing attention. There are various methods of manufacturing lignocellulosic material based thermo-plastic polymer composites, depending on the processing technique. This guarantees a continuous fiber supply at all times around the year, and it provides a significant material cost saving to the plastics industry. Synthetic fibers, such as glass and carbon fibers, are brittle and are often broken into smaller fragments (Hancox 2001), while lignocellulosic fibers are flexible and will not fracture when they are processed over sharp curvatures. This permits a high volume fraction filling during processing, which results in high mechanical properties as compared to the problems associated with abrasive synthetic fibers, especially when using glasses and ceramics. All of these features enable the fibers to maintain the desired aspect ratio for good performance of the prepared composites (Shaw 2002; Tserki et al. 2005). Moreover, lignocellulosic-based fibers offer a high ability for surface modification, an eco-friendly approach, a non-toxic nature, easy handling, and they present no health problems characteristic of most synthetic fibers, which cause skin irritations and respiratory disease (Hattotuwa et al. 2002; Yang et al. 2004). Many authors (Bledzki and Gassan, 1999; Jayaraman, 2003; Lee et al. 2004; Kim et al. 2004; Yang et al. 2004) have carried out studies on the mechanical properties of natural fiber-filled thermo-plastics. Similarly, the dispersion characteristics of yellow poplar wood fibers in cellulose acetate butyrate/ yellow poplar wood fiber composites have been studied by Onyeagoro (2012). Medium-density fiber board has become one of the most popular wood-based composite materials due to its numerous advantages and favorable machining properties. Many successful attempts have been reported to produce medium-density fiber board or other composite panels using various lignocellulosic materials (Li et al.2013). Globally, wheat and rice are the most important food grains, ranking second and third in terms of total cereal production (Halvarsson et al. 2008), and seem to be the most promising agriculture residues for manufacturing different composites.

CONCLUDED REMARKS AND FUTURE OUTLOOK

  1. The energy and environmental crises that the world is experiencing are forcing people to re-evaluate the efficient utilization of or to find alternative uses for natural, renewable resources, using clean technologies.
  2. Lignocellulosic biomass holds considerable potential for renewable fuels such as the production of bio-ethanol to meet the current energy demand of the modern world.
  3. Lignocellulosic materials offer significant opportunities to developing countries in the area of lignocellulose biotechnology to utilize the readily available residual plant biomass to produce numerous value-added products.
  4. In the current scenario, future trends are being directed toward lignocellulose biotechnology for improved processes and products.
  5. To overcome the current energy problems, it is envisaged that lignocellulosic materials in addition to green chemistry will be a main focus of future research.

ACKNOWLEDGMENTS

This study was supported by the Cavendish Research Scholarship provided by the University of Westminster London UK.

REFERENCES CITED

Abbasi, T., and Abbasi, S.A. (2010). “Biomass energy and the environmental impacts associated with its production and utilization,” Renew Sustain. Energy Rev. 14, 919-937.

Adamović, M., Grubić, G.,Milenković, I., Jovanović, R., Protić, R., Sretenović, L., and Stoićević, L. (1998). “The biodegradation of wheat straw by Pleurotus ostreatus mushrooms and its use in cattle feeding,” Anim. Feed Sci. Technol. 71, 357-362.

Ahmed, I., Zia, M. A., Iftikhar, T., and Iqbal, H. M. H. (2011). “Characterization and detergent compatibility of purified protease produced from Aspergillus niger by utilizing agro wastes,”BioResources 6(4), 4505-4522.

Alam, M. Z., Kabbashi, N. A., and Ismail, M. H. (2007). “Direct bioconversion of agriculture waste rice straw in to bioethanol,” J. Environ. Res. Dev. 2, 118-125.

Alonso, A., Pérez, P., Morcuende, R., and Martinez‐Carrasco, R. (2008). “Future CO2 concentrations, though not warmer temperatures, enhance wheat photosynthesis temperature responses,” Physiol. Plantarum. 132, 102-112.

Alvira, P., Tomás-Pejó, E., Ballesteros, M., and Negro, M. J. (2010). “Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: A review,” Biores. Technol. 101(13), 4851-4861.

Ander, P., and Eriksson, K. E. (2006). “Selective degradation of wood components by white‐rot fungi,” Physiologia plantarum. 41(4), 239-248.

Andrade de Sá, S., Palmer, C., and Engel, S. (2011). “Ethanol production, food and forests,” Environ. Res. Econ. 1-21.

Asgher, M., Ahmad, Z., and Iqbal, H. M. N. (2013). “Alkali and enzymatic delignification of sugarcane bagasse to expose cellulose polymers for saccharification and bio-ethanol production,” Ind. Crop. Prod. 44, 488-495.

Asgher, M., Ahmed, N., and Iqbal, H. M. N. (2011). “Hyperproductivity of extracellular enzymes from indigenous white rot fungi (P. chrysosporium IBL-03) by utilizing agro-wastes,” BioResources 6(4), 4454-4467.

Asgher, M., and Iqbal, H. M. N. (2011). “Characterization of a novel manganese peroxidase purified from solid state culture of Trametes versicolor IBL-04,”BioResources 6(4), 4302-4315.

Asgher, M., and Iqbal, H.M.N. (2013). “Enhanced catalytic features of sol-gel immobilized MnP isolated from solid state culture of Pleurotus ostreatus IBL-02,” Chin. Chem. Lett. 24, 344-346.

Asgher, M., Bhatti, H. N., Ashraf, M., and Legge, R. L. (2008). “Recent developments in biodegradation of industrial pollutants by white rot fungi and their enzyme system,” Biodegradation 19, 771-783.

Asgher, M., Iqbal, H. M. N., and Asad, M. J. (2012a). “Kinetic characterization of purified laccase produced from Trametes versicolor IBL-04 in solid state bio-processing of corncobs,” BioResources 7, 1171-1188.

Asgher, M., Iqbal, H. M. N., and Irshad, M. (2012b). “Characterization of purified and xerogel immobilized novel lignin peroxidase produced from Trametes versicolor IBL-04 using solid state medium of corncobs,” BMC Biotechnol. 12(1), 46. doi:10.1186/1472-6750-12-46.

Asgher, M., Irshad, M., and Iqbal, H.M.N. (2012c). “Purification and characterization of LiP produced by Schyzophyllum commune IBL-06 using banana stalk in solid state cultures,”BioResources 7(3), 4012-4021.

Bajpai, P. (1999). “Application of enzymes in the pulp and paper industry,” Biotechnol. Prog. 15, 147-157.

Bajpai, P. K., Singh, I., and Madaan, J. (2013). “Tribological behaviour of natural fiber reinforced PLA composites,” Wear. 297, 829-840.

Bajpai, P., Bajpai, P. K., and Akhtar, M. (2003). “Process for producing pulp from Eucalyptus chips,” US Patent 6613192.

Balat, M., and Balat, H. (2009). “Recent trends in global production and utilization of bio-ethanol fuel,” Applied Energy86(11), 2273-2282.

Baldrian, T., and Gabriel, J. (2003). “Lignocellulose degradation by Pleurotus ostreatus in the presence of cadmium,” FEMS Microbiol. Lett. 220, 235-240.

Bandounas, L., Wierckx, N. J. P., de Winde, J. H., and Ruijssenaars, H. J. (2011). “Isolation and characterization of novel bacterial strains exhibiting ligninolytic potential,” BMC Biotechnol.11, 94.

Beauchemin, K. A., Colombatto, D., Morgavi, D. P., and Yang, W. Z. (2003). “Use of exogenous fibrolytic enzymes to improve animal feed utilisation by ruminants,” J. Anim. Sci. 81(E. Suppl.2), E37-E47.

Bertero, M., de la Puente, G., and Sedran, U. (2012). “Fuels from bio-oils: Bio-oil production from different residual sources, characterization and thermal conditioning,” Fuel. 95, 263-271.

Bhat, M. K. (2000). “Research review paper: Cellulases and related enzymes in biotechnology,” Biotechnol. Adv.18, 355-383.

Bosco, F., Ruggeri, B., and Sassi, G. (1999). “Performances of a trickle bed reactor (TBR) for exoenzyme production by Phanerochaete chrysosporium: Influence of a superficial liquid velocity,” Chem. Eng. Sci. 54, 3163-3169.

Calvo‐Flores, F. G., and Dobado, J. A. (2010). “Lignin as renewable raw material,” Chem. Sus. Chem. 3(11), 1227-1235.

Canilha, L., Almeida, S. J. B., and Solenzal, A. I. N. (2004). “Eucalyptus hydrolysate detoxification with activated charcoal adsorption or ionexchanger resins for xylitol production,” Proc. Biochem. 39, 1909-1912.

Cardona, C. A., and Sánchez, Ó. J. (2007). “Fuel ethanol production: Process design trends and integration opportunities,” Biores. Technol. 98(12), 2415-2457.

Carvalho, W., Santos, J. C., Canilha, L., Silva, S. S., Perego, P., and Converti, A. (2005). “Xylitol production from sugarcane bagasse hydrolysate: Metabolic behaviour of Candida guilliermondii cells entrapped in Ca-alginate,” Biochem. Eng. J. 25, 25-31.

Chandel, A. K., and Singh, O. V. (2011). “Weedy lignocellulosic feedstock and microbialmetabolic engineering: Advancing the generation of ‘Biofuel’,” App. Microbiol. Biotechnol. 89, 1289-1303.

Chandel, A. K., da Silva, S. S., Carvalho, W., and Singh, O. V. 2011). “Sugarcane bagasse and leaves: Foreseeable biomass of biofuels and bioproducts,” J. Chem. Technol. Biotechnol. 87, 11-20.

Chandra, R., Bura, R., Mabee, W., Berlin, A., Pan, X., and Saddler, J. (2007). “Substrate pretreatment: The key to effective enzymatic hydrolysis of lignocellulosics?,” Biofuels. 67-93.

Chen, F., and Dixon, R. A. (2007). “Lignin modification improves fermentable sugar yields for biofuel production,” Nat. Biotechnol. 25, 759-761.

Chen, S., Zhang, X., Singh, D., Yu, H., and Yang, X. (2010). “Biological pretreatment of lignocellulosics: Potential, progress and challenges,” Biofuels. 1, 177-199.

Cherubini, F., and Ulgiati, S. (2010). “Crop residues as raw materials for biorefinery systems A LCA case study,” Appl. Energy87, 47-57.

Cohen, R., Persky, L., and Hadar, Y. (2002). “Biotechnological applications and potential of wood-degrading mushrooms of the genus Pleurotus,” Appl. Microbiol. Biotechnol. 58(5), 582-594.

Couto, S. R., and Sanromán, M. A. (2005). “Application of solid-state fermentation to ligninolytic enzyme production,” Biochem. Eng. J. 22(3), 211-219.

Couto, S. R., and Sanromán, M. A. (2006). “Application of solid-state fermentation to food industry – A review,” J. Food Eng. 76(3), 291-302.

Deng, L. H., Wang, Y. H., Zhang, Y., and Ma, R. Y. (2006). “The enhancement of ammonia pretreatment on the fermentation of rice straw hydrolysate to xylitol,” J. Food Biochem. 31, 195-205.

El-Gammal, A. A., Kamel, Z., Adeeb, Z., and Helmy, S. M. (1998). “Biodegradation of lignocellulosic substances and production of sugars and lignin degradation inter-mediates by four selected microbial strains,” Polym. Degrad. Stabil. 61, 535-542.

Elisashvili, V., Kachlishvili, E., and Penninckx, M. (2008). “Effect of growth substrate, method of fermentation, and nitrogen source on lignocellulose-degrading enzymes production by white-rot basidiomycetes,” J. Ind. Microbiol. Biotechnol. 35(11), 1531-1538.

Elisashvili, V., Penninckx, M., Kachlishvili, E., Asatiani, M. and Kvestiadze, G. (2006). “Use of Pleurotus dryinus for lignocellulolytic enzymes production in submerged fermentation of mandarin peels and tree leaves,” Enz. Microb. Tech. 38, 998-1004.

El-Nasser, N. H. A., Helmy, S. M., and El-Gammal, A. A. (1997). “Formation of enzymes by biodegradation of agricultural wastes with rot fungi,” Polym. Degrad. Stabil. 55, 249-253.

Eun, J. S., Beauchemin, K. A., Hong, S. H., and Bauer, M. W. (2006). “Exogenous enzymes added to untreated or ammoniated rice straw: Effects on in vitro fermentation characteristics and degradability,” Anim. Feed Sci. Technol. 131, 87-102.

Fitz-Patrick, M., Champagne, P., Cunningham, M. F., and Whitney, R.A. (2010). “A biorefinery processing perspective: Treatment of lignocellulosic materials for the production of value-addued products,” Biores. Technol. 101, 8915-8922.

Fu, J., Li, X., Gao, W., Wang, H., Cavaco-Paulo, A., and Silva, C. (2012). “Bio-processing of bamboo fibres for textile applications: A mini review,” Biocatal. Biotransform. 30(1), 141-153.

Ghosh, P., and Singh, A. (1993). “Physicochemical and biological treatments for enzymatic/microbial conversion of lignocellulosic biomass,” Adv. Appl. Microbiol. 39, 295-333.

Gnansounou, E. (2011). “Assessing the sustainability of biofuels: A logic-based model,” Energy. 36(4), 2089-2096.

Goldemberg, J., Coelho, S. T., and Guardabassi, P. (2008). “The sustainability of ethanol production from sugarcane,” Energy Policy. 36(6), 2086-2097.

Guimarães, J. L., Frollini, E., Da Silva, C. G., Wypych, F., and Satyanarayana, K. G. (2009). “Characterization of banana, sugarcane bagasse and sponge gourd fibers of Brazil,” Ind. Crop. Prod. 30(3), 407-415.

Gupta, N. (2007). “Effect of various fillers on physical and optical properties of agro straw paper,” Thesis, Master of Technology (M.Tech.) in Material Science and Engineering, School of Physics and Material Sciences, Thapar University, Patiala (Punjab)-147004, India.

Habibi, Y., El-Zawawy, W. K., Ibrahim, M. M., and Dufresne, A. (2008). “Processing and characterization of reinforced polyethylene composites made with lignocellulosic fibers from Egyptian agro-industrial residues,” Compos. Sci. Technol. 68(7), 1877-1885.

Halvarsson, S., Edlund, H., and Norgren, M. (2008). “Properties of medium-density fiberboard (MDF) based on wheat straw and melamine modified urea formaldehyde (UMF) resin,” Ind. Crop. Prod. 28, 37-46.

Hamzeh, Y., Ashori, A., Khorasani, Z., Abdulkhani, A., and Abyaz, A. (2013). “Pre-extraction of hemicelluloses from bagasse fibers: Effects of dry-strength additives on paper properties,” Ind. Crop. Prod. 43, 365-371.

Hancox, L. (2001). “Thermoplastic composite manufacture: Opportunities and Challenges,” J. Macromol. Sci. Dev. Macromol. Chem. Phys. CI9, 481.

Harun, N. A. F., Samsu Baharuddin, A., Mohd Zainudin, M. H., Bahrin, E. K., Naim, M. N., and Zakaria, R. (2013). “Cellulase production from treated oil palm empty fruit bunch degradation by locally isolated Thermobifida fusca,”BioResources 8(1), 676-687.

Hattotuwa, G., Premalal, B., Ismail, H., and Baharin, A. (2002). “Comparison of the mechanical properties of rice husk powder filled polypropylene composites with talc filled polypropylene composites,” Polym. Test. 7, 833-839.

Havimo, M., and Hari, P. (2010). “Temperature gradient in wood during grinding,” Appl. Math. Mod. 34(10), 2872-2880.

Howard, R. L., Abotsi, E., Jansen van Rensburg, E. L., and Howard, S., (2003). “Lignocellulose biotechnology: Issues of bioconversion and enzyme production,” Afr. J. Biotechnol. 2, 602-619.

Hu, G., Heitmann, J. A., and Rojas, O. J. (2008). “Feedstock pretreatment strategies for producing ethanol from wood, bark, and forest residues,” BioResources (3(1), 270-294.

Hüttermann, A., Hamza, A. S., Chet, I., Majcherczyk, A., Fouad, T., Badr, A., and Hadar, Y. (2000). “Recycling of agricultural wastes by white-rot fungi for the production of fodder for ruminants,” Agro Food Ind. Hi-Tech. 11(6), 29-32.

Iqbal, H. M. N., Ahmed, I., Zia, M. A., and Irfan, M., (2011a). “Purification and characterization of the kinetic parameters of cellulase produced from wheat straw by Trichoderma viride under SSF and its detergent compatibility,” Adv. Biosci. Biotechnol. 2(3), 149-56.

Iqbal, H. M. N., Asgher M., and Bhatti, H. N. (2011b). “Optimization of physical and nutritional factors for synthesis of lignin degrading enzymes by a novel strain of Trametes versicolor,” BioResources 6, 1273-1278.

Iqbal, H., and Asgher, M. (2013). “Characterization and decolorization applicability of xerogel matrix immobilized manganese peroxidase produced from Trametes versicolor IBL-04,” Prot. Pept. Lett. 20(5), 591-600.

Irshad, M., Anwar, Z., and Afroz, A. (2012a). “Characterization of Exo 1, 4-β glucanase produced from Tricoderma viridi through solid-state bio-processing of orange peel waste,” Adv. Biosci. Biotechnol. 3, 580-584.

Irshad, M., Anwar, Z., But, H. I., Afroz, A., Ikram, N., and Rashid, U. (2013). “The industrial applicability of purified cellulase complex indigenously produced by Trichoderma viride through solid-state bio-processing of agro-industrial and municipal paper wastes,”BioResources 8(1), 145-157.

Irshad, M., Asgher, M., Scheikh, M. A., and Nawaz, H. (2011). “Purification and characterization of laccase produced by Schyzophylum commune IBL-06 in solid state culture of banana stalks,” BioResources 6(3), 2861-2873.

Irshad, M., Bahadur, B. A., Anwar, Z., Yaqoob, M., Ijaz, A., and Iqbal, H. M. N. (2012b). “Decolorization applicability of sol-gel matrix-immobilized laccase produced from Ganoderma leucidum using agro-industrial waste,” BioResources 7(3), 4249-4261.

Isikhuemhen, O. I., Zadrazil, F., and Fasidi, I. (1996). “Cultivation of white rot fungi in solid state fermentation,” J. Sci. Ind. Res. 55, 388-393.

Isroi, Millati, R., Syamsiah, S., Niklasson, C., Cahyanto, M. N., Lundquist, K., and Taherzadeh, M. J. (2011). “Biological pretreatment of lignocelluloses with white-rot fungi and its applications: A review,” BioResources 6(4), 5224-5259.

Jecu, L. (2000). “Solid-state fermentation of agricultural wastes for endoglucanase production,” Ind. Crop. Prod. 11, 1-5.

Ji, X. J., Huang, H., Nie, Z. K., Qu, L., Xu, Q., and Tsao, G. (2012). “Fuels and chemicals from hemicellulose sugars,” Adv. Biochem. Engin/Biotechnol. 128, 199-224.

Jiang, G., Nowakowski, D. J., and Bridgwater, A. V. (2010). “A systematic study of the kinetics of lignin pyrolysis,” Thermochimica Acta. 498(1), 61-66.

John, F., Monsalve, G., Medina, P. I. V., and Ruiz, C. A. A (2006). “Ethanol production of banana shell and cassava starch,” Dyna. Univ. Nacional de Colomb. 73, 21-27.

Kachlishvili, E., Penninckx, M. J., Tsiklauri, N., and Elisashvili, V. (2006). “Effect of nitrogen source on lignocellulolytic enzyme production by white-rot basidiomycetes under solid-state cultivation,” World J. Microbiol. Biotechnol. 22(4), 391-397.

Kamat, S., Khot, M., Zinjarde, S., Kumar, A. R., and Gade, W. N. (2012). “Coupled production of single cell oil as biodiesel feedstock, xylitol and xylanase from sugarcane bagasse in a biorefinery concept using fungi from the tropical mangrove wetlands,” Biores. Technol. http://dx.doi.org/10.1016/j.biortech.2012.11.059.

Kansoh, A. L., Essam, S. A., and Zeinat, A. N. (1999). “Biodegradation and utilization of bagasse with Trichoderma reesie,” Polym. Degrad. Stabil. 63, 273-278.

Kim, M., and Day, D. F. (2011). “Composition of sugar cane, energy cane, and sweet sorghum suitable for ethanol production at Louisiana sugar mills,” J. Ind. Microbiol. Biotechnol. 38(7), 803-807.

Kumar, P., Barrett, D. M., Delwiche, M. J., and Stroeve, P. (2009). “Methods for pretreament of lignocellulosic biomass for efficient hydrolysis and biofuel production,” Ind. Eng. Chem. 48, 3713-3729.

Kumar, R., Singh, S., and Singh, O. V. (2008). “Bioconversion of lignocellulosic biomass: biochemical and molecular perspectives,” J. Ind. Microbiol. Biotechnol. 35(5), 377-391.

Levin, L., Herrmann, C., and Papinutti, V. L. (2008). “Optimization of lignocellulolytic enzyme production by the white-rot fungus Trametes trogii in solid-state fermentation using response surface methodology,” Biochem. Eng. J. 39, 207-214.

Li, X., Wu, Y., Cai, Z., and Winandy, J. E. (2013). “Primary properties of MDF using thermo-mechanical pulp made from oxalic acid pretreated rice straw particles,” Ind. Crop. Prod. 41, 414-418.

Lin, Y., and Tanaka, S. (2006). “Ethanol fermentation from biomass resources: Current state and prospects,” Appl. Microbiol. Biotechnol. 69, 627-642.

Lucia, L. A. (2008). “Lignocellulosic biomass: A potential feedstock to replace petroleum,” BioResources 3(4), 981-982.

Malherbe, S., and Cloete, T. E. (2002). “Lignocellulose biodegradation: Fundamentals and applications,” Rev. Environ. Sci. Biotechnol. 1, 105-114.

Manda, B. M., Blok, K., and Patel, M. K. (2012). “Innovations in papermaking: An LCA of printing and writing paper from conventional and high yield pulp,” Sci. Total Environ. 439, 307-320.

Mathews, J. A. (2007). “Biofuels: What a Biopact between North and South could achieve,” Energy Policy. 35(7), 3550-3570.

McKendry, P., (2002). “Energy production from biomass: Overview of biomass,” Biores. Technol. 83, 37-43.

Medina, E., Paredes, C., Perez-Murcia, M., Bustamante, M., and Moral, R. (2009). “Spent mushroom substrates as component of growing media for germination and growth of horticultural,” Biores. Technol. 100, 4227-4232.

Messner, K., Koller, K., Wall, M. B., Akther, M., and Scott, G. M. (1998). “Fungal treatment of wood chips for chemical pulping,” In: Young, R. A., and Akther, M. (eds.), Environmentally Friendly Technologies for the Pulp and Paper Industry, John Wiley and Sons, Inc., pp. 385-398.

Misra, S., Raghuwanshi, S., and Saxena, R. K. (2013). “Evaluation of corncob hemicellulosic hydrolysate for xylitol production by adapted strain of Candida tropicalis,” Carbohydr. Polym. 92, 1596-1601.

Moldes, A. B., Bustos, G., Torrado, A., and Dominguez, J. M. (2007). “Comparison between different hydrolysis processes of vine-trimming waste to obtain hemicellulosic sugars for further lactic acid conversion,” Appl. Biochem. Biotechnol. 143, 244-256.

Moldes, D., Lorenzo, M., and Sanroman, M.A. (2004). “Different proportions of laccase isoenzymes produced by submerged cultures of Trametes versicolor grown on lignocellulosic wastes,” Biotechnol. Lett. 26, 327-330.

Nigam, P., and Singh, D. (1996). “Processing of agricultural wastes in solid state fermentation for microbial protein production,” J. Sci. Ind. Res. 55, 373-380.

Oberoi, H. S., Chavan, Y., Bansal, S., and Dhillon, G. S. (2010). “Production of cellulases through solid state fermentation using kinnow pulp as a major substrate,” Food Bioproc. Technol. 3(4), 528-536.

Pal, S., Banik, S.P., and Khowala, S. (2013). “Mustard stalk and straw: A new source for production of lignocellulolytic enzymes by the fungus Termitomyces clypeatus and as a substrate for saccharification,” Ind. Crops Prod. 41, 283-288.

Papinutti, L., and Lechner, B. (2008). “Influence of the carbon source on the growth and lignocellulolytic enzyme production by Morchella esculenta strains,” J. Ind. Microbiol. Biotechnol. 35(12), 1715-1721.

Papinutti, V. L., and Forchiassin, F. (2007). “Lignocellulolytic enzymes from Fomes sclerodermeus growing in solid-state fermentation,” J. Food Eng. 81(1), 54-59.

Paredes, C., Medina, E., Moral, R., Pérez-Murcia, M. D., Moreno-Caselles, J., Bustamante, M. A., and Cecilia, J. A. (2009). “Characterization of the different organic matter fractions of spent mushroom substrate,” Commun. Soil Sci. Plant Anal. 40, 150-161.

Pérez, J., Muñoz-Dorado de la Rubia T., and Martínez, J. (2002). “Biodegradation and biological treatments of cellulose, hemicellulose and lignin: An overview,” Int. Microbiol. 5, 53-63.

Phan, C. W., and Sabaratnam, V. (2012). “Potential uses of spent mushroom substrate and its associated lignocellulosic enzymes,” Appl. Microbiol. Biotechnol. 96, 863-873.

Pluske, J. R., and Lindemann, M. D. (1998). “Enzyme supplementation of pig and poultry diets,” In: T. P. Lyons and K. A. Jacques (eds.), Proceedings of the Alltech’s 14th Annual Symposium, Passport to the Year 2000, Biotechnology in the Feed Industry, Nottingham University Press, UK, pp. 375-392.

Pokhrel, D., and Viraraghavan, T. (2004). “Treatment of pulp and paper mill wastewater A review,” Sci. Total Environ. 333, 37-58.

Prassad, S., Singh, A., and Joshi, H.C. (2007). “Ethanol as an alternative fuel from agricultural, industrial and urban residues,” Res. Conserv. Recycl. 50, 1-39.

Rademacher, W. (2004). “Prohexadione-Ca induces resistance to fire blight and other diseases,” EPPO Bull. 34, 383-388.

Reddy, G. V., Ravindra Babu, P., Komaraiah, P., Roy, K. R. R. M., and Kothari, I. L. (2003). “Utilization of banana waste for the production of lignolytic and cellulolytic enzymes by solid substrate fermentation using two Pleurotus species P. ostreatus and P. sajorcaju,” Proc. Biochem. 38(10), 1457-1462.

Reijnders, L., and Huijbregts, M. A. (2007). “Life cycle greenhouse gas emissions, fossil fuel demand and solar energy conversion efficiency in European bioethanol production for automotive purposes,” J. Cleaner. Prod. 15(18), 1806-1812.

Rohowsky, B., Häßler, T., Gladis, A., Remmele, E., Schieder, D., and Faulstich, M. (2013). “Feasibility of simultaneous saccharification and juice co-fermentation on hydrothermal pretreated sweet sorghum bagasse for ethanol production,” Appl. Energy. 102, 211-219.

Ruggeri, B., and Sassi, G. (2003). “Experimental sensitivity analysis of a trickle bed bioreactor for lignin peroxidases production by Phanerochaete chrysosporiumProc. Biochem.38(12), 1669-1676.

Sakamoto, T., Hasunuma, T., Hori, Y., Yamada, R., and Kondo, A. (2012). “Direct ethanol production from hemicellulosic materials of rice straw by use of an engineered yeast strain codisplaying three types of hemicellulolytic enzymes on the surface of xylose-utilizing Saccharomyces cerevisiae cells,” J. Biotechnol. 158(4), 203-210.

Sánchez, C. (2009). “Lignocellulosic residues: Biodegradation and bioconversion by fungi,” Biotechnol. Adv. 27(2), 185-194.

Saritha, M., and Arora, A. (2012). “Biological pretreatment of lignocellulosic substrates for enhanced delignification and enzymatic digestibility,” Ind. J. Microbiol. 52(2), 122-130.

Sarrouh, B. F., de Freitas Branco, R., and da Silva, S. S. (2009). “Biotechnological production of xylitol: Enhancement of monosaccharide production by post-hydrolysis of dilute acid sugarcane hydrolysate,” Appl. Biochem. Biotechnol. 153, 163-170.

Shahriarinour, M., Ramanan, R. N., Abdul Wahab, M. N., Mohamad, R., Mustafa, S., and Ariff, A. B. (2011). “Improved cellulase production by Aspergillus terreus using oil palm empty fruit bunch fiber as substrate in a stirred tank bioreactor through optimization of the fermentation conditions,”BioResources 6(3), 2663-2675.

Shahsavarani, H., Hasegawa, D., Yokota, D., Sugiyama, M., Kaneko, Y., Boonchird, C., and Harashima, S. (2013). “Enhanced bio-ethanol production from cellulosic materials by semi-simultaneous saccharification and fermentation using high temperature resistant Saccharomyces cerevisiae TJ14,” J. Biosci. Bioeng. 115, 20-23.

Shaw, J. (2002). “Cellulose derivatives,” Adv. Polym. Sci. 105, 224-231.

Shuit, S. H., Tan, K. T., Lee, K. T., and Kamaruddin, A. H. (2009). “Oil palm biomass as a sustainable energy source: A Malaysian case study,” Energy, 34(9), 1225-1235.

Silva, E. M., Machuca, A., and Milagres, A. M. F. (2005). “Effect of cereal brans on Lentinula edodes growth and enzyme activities during cultivation on forestry waste,” Lett. Appl. Microbiol. 40(4), 283-288.

Singh, P., Sulaiman, O., Hashim, R., Peng, L. C., and Singh, R. P. (2012). “Using biomass residues from oil palm industry as a raw material for pulp and paper industry: Potential benefits and threat to the environment,” Environ. Develop. Sustainab. 1-17. DOI 10.1007/s10668-012-9390-4.

Singh, P., Sulaiman, O., Hashim, R., Rupani, P. F., and Peng, L. C. (2010). “Biopulping of lignocellulosic material using different fungal species: a review,” Rev. Environ. Sci. Biotechnol. 9(2), 141-151.

Stoilova, I., Krastanov, A., and Stanchev, V. (2010). “Properties of crude laccase from Trametes versicolor produced by solid-substrate fermentation,” Adv. Biosci. Biotechnol. 1, 208-215.

Sukumaran, R. K., Singhania, R. R., Mathew, G. M., and Pandey, A. (2009). “Cellulase production using biomass feedstock and its application in lignocellulose saccharification for bio-ethanol production,” Renew. Energy 34(2), 421-424.

Tengerdy, R. P., Szakacs, G., and Sipocz, J. (1996). “Bioprocessing of sweet sorghum with in situ produced enzymes,” Appl. Biochem. Biotechnol. 57/58, 563-569.

Tserki, V., Matzinos, P., Kokkou, S., and Panayiotou, C. (2005). “Novel biodegradable composites based on treated lignocellulosic waste flour as filler-Part I: Surface chemical modification and characterization of waste flour,” Compos. Part A. 36, 965-974.

Tuncer, M., Kuru, A., Sahin, N., Isikli, M., and Isik, K. (2009). “Production and partial characterization of extracellular peroxidase produced by Streptomyces sp. F6616 isolated in Turkey,” Ann. Microbiol. 59(2), 323-334.

Varanasi, P., Singh, P., Auer, M., Adams, P.D., Simmons, B.A., and Singh, S. (2013). “Survey of renewable chemicals produced from lignocellulosic biomass during ionic liquid pretreatment,” Biotechnol. Biofuels 6(1), 14. doi:10.1186/1754-6834-6-14.

West, T. P. (2009). “Xylitol production by Candida species grown on a grass hydrolysate,” World J. Microbiol. Biotechnol. 25, 913-916.

Xia, L., and Len, P. (1999). “Cellulose production by solid-state fermentation on lignocellulosic waste from the xylose industry,” Proc. Biochem. 34, 909-912.

Yang, B., and Wyman, C. E. (2008). “Pretreatment: The key to unlocking low-cost cellulosic ethanol,” Biofuels. Bioprod. Bioref.2, 26-40.

Yang, B., Dai, Z., Ding, S.-Y., and Wyman, C. E. (2011). “Enzymatic hydrolysis of cellulosic biomass,” Biofuels 2(4), 421-450.

Yang, H. S., Kim, H. J., Son, J., Park, H. J., Lee, B. J., and Hwang, T. S. (2004). “Rice husk flour filled polypropylene composites: Mechanical and morphological study,” Compos. Struct. 63(3), 305-312.

Yang, X., Chen, H., Gao, H., and Li, Z. (2001). “Bioconversion of corn straw by coupling ensiling and solid-state fermentation,” Biores.Technol. 78, 277-280.

Yoon, L. W., Ngoh, G. C., and Chua, A. S. M. (2012). “Simultaneous production of cellulase and reducing sugar from alkali-pretreated sugarcane bagasse via solid state fermentation,”BioResources 7(4), 5319-5332.

Zhu, H., Sheng, K., Yan, E., Qiao, J., and Lv, F. (2012). “Extraction, purification and antibacterial activities of a polysaccharide from spent mush room substrate,” Int. J. Biol. Macromol. 50, 840-843.

Zhu, Y., Lee, Y.Y., and Elander, R.T. (2005). “Optimization of dilute-acid pretreatment of corn stover using a high-solids percolation reactor,” Appl. Biochem. Biotechnol. 121-124, 1045-1054.

Article Submitted: January 4th, 2013; Peer review completed: February 10, 2013; Revised version received: April 10; Accepted April 11, 2013; Published: April 24, 2013.