Persulfate based pretreatment to enhance the enzymatic digestibility of rice straw

doi:10.1016/j.biortech.2016.09.122

Bioresource Technology

Volume 222, December 2016, Pages 523-526

https://doi.org/10.1016/j.biortech.2016.09.122 Get rights and content

Highlights

•
Potassium persulfate is a good oxidative pretreatment reagent.
•
The highest enzymatic digestibility of 91% was achieved.
•
Persulfate based oxidation significantly altered the structural features.

Abstract

Oxidation induced by potassium persulfate was evaluated as an economic substitute for the Fenton-like reaction for the purpose of rice straw pretreatment in terms of temperature (80–140 °C), potassium persulfate concentration (5–100 mM) and process time (0.5–3 h), an optimal pretreatment condition was identified: 120 °C for 2 h with 75 mM potassium persulfate concentration and yielded 91% enzymatic digestibility using 25.2 FPU/g of biomass. Crystallinity index, SEM and SEM-EDS analyses revealed that biomass was indeed disrupted and components like silica were exposed. All this suggested that this persulfate-based pretreatment method, which is distinctively advantageous in terms of effectiveness and economics, can indeed be a competitive option.

Introduction

Increasing future energy demand and yet finite fossil fuel reserves, together with climate changes, are overriding concerns that our world will face. These daunting challenges have created keen interest in nonconventional sources of energy-this is more so today than perhaps ever before (Sindhu et al., 2016). Renewable energy sources, specifically biofuels, can be a solution to it in general and probably the only alternative in the transportation sector at least for a while (Sarkar et al., 2012). Cellulosic biomass, being abundant and locally available is a practical feedstock not only for the biofuels but also for biorefinery (Wang et al., 2011).

Lignocellulosic biomass, within its native matrix, consists of cellulose and hemicellulose surrounded by lignin sheath. This structure, which is complex and strong, makes sugars of cellulose and hemicellulose only restrictedly available for the downstream bioprocessing (Haykir et al., 2013). It is this reason that the biomass must be disintegrated before any use (Tye et al., 2016). This step of disintegration called as pretreatment accounts for one third of production cost and serves as a hurdle to the commercial development of lignocellulosic bioethanol production (Lynd, 1996).

Many pretreatment methods have been developed; and examples include alkali treatment, acid hydrolysis, steam explosion, hot water treatment, supercritical carbon dioxide explosion, ammonia fiber explosion, extrusion pretreatment, hydrodynamic cavitation and biological processes (Mussatto and Dragone, 2016, Hamelinck et al., 2005, Terán Hilares et al., 2016, Al-Zuhair et al., 2013). Although these pretreatment means are powerful in terms of effectiveness, they still lack economical viability. For example, even in the most well-established H₂SO₄-based pretreatment, the need of corrosion resistant reactor, neutralization of pretreated biomass and the formation of fermentative inhibitory products are overwhelming, making it rather an expensive choice (Zheng et al., 2009). A sufficiently effective and yet economically competitive method is still needed to make full advantage of the potential of lignocellulose for the purpose of the production of fuels and bio-chemicals (Wyman et al., 2005).

Recently the Fenton-like reactions have been suggested as a treatment option for lignocelluloses (Jeong and Lee, 2016, Jung et al., 2015, Kato et al., 2014, He et al., 2015, Michalska and Ledakowicz, 2016), just like above mentioned applications. In this approach, hydroxyl radicals are generated, disrupting the biomass structure in an oxidative manner, which thereby enhance the enzymatic digestibility by way of changing crystallinity and surface features of biomass.

Sulfate radicals (SO₄⁻) principally do the same; and because of its substantially low price and easy storage it can easily replace the hydroxyl radicals (Seo et al., 2016). The sulfate radicals can be generated from persulfate anions by simple heating (Graham, 2007). During heat activation, peroxide bond in a persulfate molecule undergoes a homolysis reaction, forming SO₄⁻ radicals (Ji et al., 2015).

In this study, therefore, potassium persulfate was adopted as a cheap and convenient replacement of the Fenton-like reagent for the pretreatment of lignocellulosic biomass. Rice straw was used as a model biomass feedstock. The effectiveness was evaluated in terms of the enzymatic digestibility and physical changes were also observed to find out causes of any such improvement.

Section snippets

Lignocellulosic preparation

Rice straw was selected as model biomass. It was collected from Nonsan City, South Korea washed and air dried prior to any processing. Milling and screening were first done to make straw particles below 2 mm. Composition analysis of untreated rice straw revealed glucan of 35.3%, xylan of 18.5%, lignin of 19.6% and ash of 12.8% all on dry weight basis.

Pretreatment

A lab scale stainless steel cylindrical reactor, with a total volume of 70 ml, was used for pretreatment. The fine rice straw particles were loaded

Effects of pretreatment temperature on enzymatic digestibility

Temperature is always a critical parameter in any chemical reaction in general and also the case in lignocellulose pretreatment. So, in order to see the effect of temperature with persulfate in relation to pretreatment efficacy, a reaction was proceeded for 2 h in the presence of 75 mM of potassium persulfate with temperature varying from 80 °C to 140 °C. Chemical composition of the pretreated biomass, along with solid recovery and enzymatic digestibility, are listed in Table 1. The solid recovery,

Conclusions

Potassium persulfate was found to be an effective oxidative reagent to pretreat rice straw. Persulfate anions, in conjunction with thermal activation, caused significant morphological changes and drastically enhanced the enzymatic digestibility. This oxidation approach, as an economical substitute for Fenton’s reactions, seems a potential addition to thus far adopted oxidative pretreatment strategies for lignocelluloses. Thus it is reasonable to envisage this as one economical option for the

Acknowledgements

This research was supported by the Advanced Biomass R&D Center (ABC) of Global Frontier Project (ABC-2011-0031348) funded by the ministry of science, ICT and future planning, and the National Research Foundation of Korea (NRF-2012M1A2A2026587) funded by the Korea government Ministry of Education, Science and Technology (MEST).

References (24)

S. Al-Zuhair et al.
Synergistic effect of pretreatment and hydrolysis enzymes on the production of fermentable sugars from date palm lignocellulosic waste
J. Ind. Eng. Chem.
(2013)
C.N. Hamelinck et al.
Ethanol from lignocellulosic biomass: techno-economic performance in short-, middle- and long-term
Biomass Bioenergy
(2005)
N.I. Haykir et al.
Pretreatment of cotton stalk with ionic liquids including 2-hydroxy ethyl ammonium formate to enhance biomass digestibility
Ind. Crops Prod.
(2013)
Y.C. He et al.
Enhancement of enzymatic saccharification of corn stover with sequential Fenton pretreatment and dilute NaOH extraction
Bioresour. Technol.
(2015)
S.-Y. Jeong et al.
Sequential Fenton oxidation and hydrothermal treatment to improve the effect of pretreatment and enzymatic hydrolysis on mixed hardwood
Bioresour. Technol.
(2016)
Y. Ji et al.
Heat-activated persulfate oxidation of atrazine: implications for remediation of groundwater contaminated by herbicides
Chem. Eng. J.
(2015)
Y.H. Jung et al.
Mimicking the Fenton reaction-induced wood decay by fungi for pretreatment of lignocellulose
Bioresour. Technol.
(2015)
D.M. Kato et al.
Pretreatment of lignocellulosic biomass using Fenton chemistry
Bioresour. Technol.
(2014)
Y.C. Lee et al.
Efficient decomposition of perfluorocarboxylic acids in aqueous solution using microwave-induced persulfate
Water Res.
(2009)
N. Sarkar et al.
Bioethanol production from agricultural wastes: an overview
Renew. Energy
(2012)

Y.H. Seo et al.

Lipid extraction from microalgae cell using persulfate-based oxidation

Bioresour. Technol.

(2016)

R. Sindhu et al.

Biological pretreatment of lignocellulosic biomass – an overview

Bioresour. Technol.

(2016)

Cited by (24)

Persulfate pretreatment facilitates decomposition of maize straw in soils and accumulation of straw residues with high adsorption capacity
2023, Chemical Engineering Journal
Because of the complex and recalcitrant structure of straw, large amounts of straw residues accumulate in soils with straw return practice, and pose various adverse impacts. In this study, both laboratory experiments and field demonstration were conducted to investigate the effects of persulfates (PS) pretreatments on structure and properties of maize straw. PS pretreatment of maize straw was developed to facilitate decomposition of returned straw in soils. Persulfates break the aryl C-O bonds of stable lignin units and destroy dense crystalline structure of cellulose units. The former impact was pronounced at high levels of PS. Both impacts were responsible for the accelerated decomposition of maize straw in field soils. The decomposition of maize straw with 0.1% PS pretreatment was increased by 29% (181 d), often superior to the biological-based methods. Interestingly, all straw residues collected in the soils with PS-treated maize straw return after 43 d displayed higher adsorption capacity of the four commonly used herbicides. The adsorption K_d values of herbicides were about 76%–123% higher than those by straw residues collected in the soils with pristine maize straw return. Additionally, all PS pretreatments posed no adverse impacts to both soil bacterial and fungi community. Some of Top Ten bacteria or fungi were stimulated, highlighted by the increases in relative abundances by 4.02%–963%. These results demonstrate that PS pretreatments can serve as an easy and applicable approach to reducing straw residues in soils. Then PS pretreatment may have environmental significance in alleviating accumulation of straw residue in soils and diffusion of pesticides into aquatic systems.
Effects of various persulfate oxidation pretreatments on enzymatic saccharification efficiency of sugarcane bagasse biomass and the related mechanism
2023, Industrial Crops and Products
This study explored the impact of different persulfate pretreatments on the substrate characteristics and enzymatic sugar yield of sugarcane bagasse (SCB) and the related mechanisms. We analyzed the biomass composition, physicochemical properties of SCB, enzymatic saccharification efficiency, pure commercial cellulose and lignin degradation dynamics, and ·OH and SO₄^{∙ −} generation properties under different persulfate pretreatments. The results revealed that potassium peroxymonosulfate (2KHSO₅·KHSO₄·K₂SO₄, PPMS) pretreatment had a significant effect on SCB. Under the optimal pretreatment conditions, SCB pretreated with PPMS showed a reducing sugar yield of 67.98%, a sugar conversion rate of 90.29%, and a lignin removal rate of 87.49%, which were about 2–3 folds those under pretreatment with peroxydisulfate (PDS) including sodium persulfate (Na₂S₂O₈, SPS) and ammonium persulfate ((NH₄)₂S₂O₈, APS). PPMS had higher selectivity for lignin degradation and stronger free radical generation ability than PDS, which may be the main contributor to its superior pretreatment performance.
Combinatorial pretreatments of reed straw using liquid hot water and lactic acid for fermentable sugar production
2023, Fuel
A green combinatorial pretreatment using liquid hot water (LHW) and lactic acid (LA) was used to treat reed straw for effective lignocellulose digestibility and xylose recovery. The reeds were first treated with LHW at 180 °C for 60 min, followed by LA treatment at 170 °C for 45 min. Using 37.5 g/L lactic acid, the lignocellulose digestibility was 80.6 % and glucose yield was 56.0 %, which was much higher than that for one-step LHW pretreatment (the lignocellulose digestibility was 27.3 % and the glucose yield was 26.3 %). These data demonstrated that LHW-LA pretreatment increased lignocellulose digestibility and glucose yield by 1.95-fold and 1.13-fold, respectively. The highest total sugar yielded 39.2 g/100 g_-substrate. The results revealed that LHW-LA pretreatment removed most hemicellulose and partial lignin from the reed straw and prompted cellulase binding to reed cellulose, which enhanced lignocellulose enzymatic saccharification. The high fermentable glucose yielded from the combinatorial pretreatment as presented in this study highlighted the great potential of our pretreatment technology to be applied in the biorefinery, which could lay down the cost and sustainability of current biorefinery industry.
Production of microcrystalline cellulose and bacterial nanocellulose through biological valorization of lignocellulosic biomass wastes
2021, Journal of Cleaner Production
Microcrystalline cellulose (MCC) and bacterial nanocellulose (BNC) are inexhaustible, natural biopolymers with many applications in various fields of modern science. In this study, the methodological approach employing cellulolytic bacterial consortium for various lignocellulose biomasses (LCB) valorization leading to production of MCC and BNC was demonstrated and evaluated. Various spectroscopy and imaging based characterizations showed that MCC prepared through valorization were microcrystalline, irregularly shaped with increased carbon content and crystallinity. When a BNC producing novel Bacillus cabrialesii strain was cultured in Hestrin-Schramm (HS) medium supplemented with reducing sugars released during valorization, ultrafine, aggregated, crystallized networks of nano-sized BNC fibrils of average length in the range of 30–62.47 nm were produced. Thus, based on the results obtained, a facile, green methodological approach has been proposed that can be used for LCB waste disposal management and its valorization for production of various value added products.
Optimization of thermally activated persulfate pretreatment of corn straw and its effect on anaerobic digestion performance and stability
2021, Biomass and Bioenergy
The effect of thermally activated persulfate on anaerobic digestion is incompletely understood. An orthogonal test was used to optimize the pretreatment process of corn straw using thermally activated persulfate, a lab-scale batch anaerobic digester was used for exploring the effect of pretreatment on anaerobic digestion. The optimal pretreatment conditions were 50 °C, 16 h, 0.5% Na₂S₂O₈, pH = 5, and solid–liquid mass ratio (S:L) = 1:10, which was the most crucial factor. Lignin pretreatment with thermally activated sodium persulfate (SPS) considerably decreased. The yield of reducing sugar (RS) and VFAs were observably higher than the untreated group. This trend occurred because the thermal activation of persulfate primarily destroys the benzene ring in lignin by generating and releasing active sulfate radical (SO₄^·−); moreover, hydroxyl radical (·OH) and SO₄⁻ work together during thermal activation. Furthermore, the daily biogas production of the groups pretreated for 16 and 48 h without elution were 22.78% and 26.80% higher than that of the group untreated, respectively. The degradation rates of total and volatile solids increased to 60% and 70% after the pretreatment. Therefore, thermally activated SPS could improve the performance and stability of anaerobic digestion, and the impact of dissolved organic matter loss exceeded that of residual Na⁺ and SO₄² ⁻.
Process optimization for chemical pretreatment of rice straw for bioethanol production
2020, Renewable Energy
Citation Excerpt :
As it can be clearly seen, there was difference in XRD peaks in untreated and ammonia pretreated biomass that clearly revealed the difference in cellulose crystallinity index of respective biomass (Fig. 3b). Two major reflections near 16° and 22° represent amorphous and crystalline components [47] in untreated and ammonium pretreated rice straw, respectively (Fig. 3b). There was comparable increment in peak around 22° in pretreated rice straw, indicated the more exposure of cellulose.
Pretreatment of rice straw was optimized by physical and chemical methods. Among all the pretreatment methods followed by saccharification, autoclaved ammonia pretreatment significantly enhanced the liberation of reducing sugars i.e. 233.76 ± 1.23 mg/g substrate as compared to other methods. Further statistical optimization by response surface methodology (RSM) including ammonia concentration, substrate concentration and autoclaving time, enhanced the saccharification rate by 1.9-fold i.e. 451.96 mg/g substrate at 5 % rice straw, 12 % ammonia and autoclave time of 30 min after saccharification of 6 h. Maximum liberation of reducing sugars (635.37 mg/g substrate) was attained under these optimized conditions at 60 °C after 48 h. Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscope analysis clearly confirmed the removal of lignin in pretreated biomass. Ammonia pretreated enzymatic hydrolysate was fermented by Saccharomyces cerevisiae at 30 °C, pH 7.0, 150 rpm and 20 % hydrolysate, resulted in 24.37 g/L bioethanol after 72 h.

View all citing articles on Scopus

View full text

Short CommunicationPersulfate based pretreatment to enhance the enzymatic digestibility of rice straw

Highlights

Abstract

Introduction

Section snippets

Lignocellulosic preparation

Pretreatment

Effects of pretreatment temperature on enzymatic digestibility

Conclusions

Acknowledgements

J. Ind. Eng. Chem.

Biomass Bioenergy

Ind. Crops Prod.

Bioresour. Technol.

Bioresour. Technol.

Chem. Eng. J.

Bioresour. Technol.

Bioresour. Technol.

Water Res.

Renew. Energy

Bioresour. Technol.

Bioresour. Technol.

Short Communication
Persulfate based pretreatment to enhance the enzymatic digestibility of rice straw