Hydrogen production by fermentative consortia

doi:10.1016/j.rser.2008.03.003

Renewable and Sustainable Energy Reviews

Volume 13, Issue 5, June 2009, Pages 1000-1013

https://doi.org/10.1016/j.rser.2008.03.003 Get rights and content

Abstract

In this work, H₂ production by anaerobic mixed cultures was reviewed. First, the different anaerobic microbial communities that have a direct relation with the generation or consumption of H₂ are discussed. Then, the different methods used to inhibit the H₂-consuming bacteria are analyzed (mainly in the methanogenesis phase) such as biokinetic control (low pH and short hydraulic retention time), heat-shock treatment and chemical inhibitors along with their advantages/disadvantages for their application on an industrial scale. After that, biochemical pathways of carbohydrate degradation to H₂, organic acids and solvents are showed. Fourth, structure, diversity and dynamics of H₂-producers communities are detailed. Later, the hydrogenase structure and activity is related with H₂ production. Also, the causes for H₂ production inhibition are analyzed along with strategies to avoid it. Finally, immobilized-cells systems are presented as a way to enhance H₂ production.

Introduction

For decades, the use and abuse of fossil fuels (either in liquid, gaseous or solid form) has caused contamination of our soil, air and water. Recently, diverse alternative fuels have been proposed to substitute fossil fuels. Hydrogen is one of these alternative fuels that is recognized as a promising future energy carrier. It is considered a clean fuel since it does not have carbon, sulfur or nitrogen that cause pollution during combustion [96]. Today, H₂ is principally produced from fossil fuels such as natural gas and naphtha. However, this practice is an environmental contradiction since a clean fuel is generated from a polluting and limited source. Therefore, it is necessary to use other sources and methods to obtain H₂ in a renewable, sustainable and environmentally friendly way.

In this regard, biotechnology can provide H₂ from renewable, cheap and abundant sources such as wastewater or organic solid wastes. This way, the use of pure cultures of anaerobes, aerobes, photosynthetic bacteria and cyanobacteria have been reported with the objective of generating H₂ [60]. Also, it is possible to use undefined microbial consortia to generate H₂ from a fermentation process. The use of fermentative consortia presents several advantages such as high H₂ generation rates (∼100 times more than with photosynthetic cultures), continuous H₂ generation at a sustained rate since it does not depend on light energy as a photosynthetic process does, generation of metabolites of commercial interest (such as organics acids and solvents), oxygen limitation does not exist because it is an anaerobic process and the most important fact is it can use complex organic waste as a substrate in non-sterile conditions [13], [46], [45]. The use of organic wastes instead of pure carbohydrates is the main advantage of the fermentative process utilizing consortia since the costs for implementation to full scale is smaller. Thus, it is possible to generate H₂ from wastewater or municipal/industrial/agricultural solid wastes, avoiding their incineration or disposal in landfills. In spite of their potential, this technology has not been studied much and there are still many limitations to overcome.

The scope of this review is to present an updated perspective presenting more than 90 publications that are direct or indirectly related with H₂ production by fermentative consortia. This search was focused on (i) H₂ evolution in anaerobic environments; (ii) induction of H₂ accumulation by biokinetic control, heat-shock treatment and chemical inhibitors; (iii) structure, diversity and dynamics of H₂-producers communities; (iv) basic biochemical aspects such as the metabolic pathways of carbohydrate anaerobic degradation into H₂; (v) hydrogenases related with H₂ evolution, focusing on conditions that affect their activity; (vi) inhibition of H₂ production by products such as organic acids/solvents and H₂ as well as the methods used to prevent that inhibition (gas sparging, membranes).

Section snippets

Hydrogen: a key intermediate in anaerobic environments

The degradation of organic matter in anaerobic environments by microbial consortia involves the cooperation of a population of microorganisms that generate a stable, self-regulating fermentation [81]. First, hydrolytic bacteria hydrolyze polymeric proteins and sugars. Then, fermentative bacteria form organic acids, H₂ and CO₂ from monomeric molecules (Fig. 1). At that point, H₂ and acetate can be utilized and/or produced by several microbial groups. Thus, acetate is generated during

Induction of H₂ accumulation in anaerobic consortia

In most anaerobic environments, the H₂ consumption is carried out very quickly by different microbial groups. Contrary to this natural fact, our interest is to propitiate the H₂ accumulation in order to use it as fuel. Therefore, H₂ accumulation is linked with the inhibition of H₂-consuming microorganisms such as hydrogenotrophic methanogens and autotrophic acetogens being the main ones when nitrate and sulphate are absent or negligible. Only a few reports have observed H₂ consumption by

Structure, diversity and dynamics of H₂-producers communities

Hydrogen production using anaerobic consortia provides many advantages, the main one being that organic waste or wastewater could be used without sterilization. This may confer large economic profits to the process. In order to enhance the process performance and maintain an attractive H₂ production, it is advisable to gain insight on the community structure and dynamics. For years, culture-based studies were carried out to maintain and evaluate process conditions. However, those techniques

Biochemical pathways for H₂ production

Fig. 7 shows the biochemical pathways utilized by clostridia for the conversion of carbohydrates to H₂, CO₂, organic acids and solvents. These biochemical pathways are similar in diverse Clostridium species, i.e., Clostridium acetobulylicum and Clostridium thermocellum except that the pathway for production of acetone and butyric are absent in C. thermocellum. According to literature, two main phases can be distinguished during the batch fermentation: the acid production phase (Fig. 7) and the

Hydrogenases

The enzymes directly involved in the metabolism of molecular H₂ are named hydrogenases and carry on the reversible oxidation of molecular H₂:H₂ ↔ 2H⁺ + 2e⁻

Hydrogen oxidation is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulphate, carbon dioxide and fumarate, whereas proton reduction (H₂ evolution) is essential in pyruvate fermentation or in the disposal of excess electrons. Many microorganisms have hydrogenases and some of these enzymes have been found to contain metal

Inhibition of H₂ generation by products

The Clostridium species have two different metabolic pathways for H₂ production from carbohydrate fermentation: acidogenesis, which produces mainly organic acids like acetate and butyrate, and solventogenesis which generates solvents such as acetone and ethanol. Thus, when environmental conditions are favorable, Clostridium is able of modify their metabolism to any of these pathways. However, only the carbohydrate fermentation during acidogenesis generates high H₂ yields [73], [34]. In this

Immobilized-cell systems

Immobilized-cell systems have become a common alternative to suspended-cell systems in continuous operation since they are more efficient in solid/liquid separation and can be operated at high dilution rates (or short retention times) without encountering washout of cells. Several studies found that immobilized-cell systems were suitable for continuous H₂ fermentation with pure cultures using a variety of natural and synthetic support matrices. However, information regarding utilization of

Conclusions and perspectives

Anaerobic consortia can be utilized for H₂ production obtaining equal performance in utilizing pure cultures. The main advantage of this process is that organic waste utilization allows working under non-sterile conditions. In this way, production may not need as much steam to achieve sterile/sanitary conditions if the are robust.

However, when non-sterile consortia are employed, H₂ and CO₂ generated are ideal food for H₂-consuming microorganisms, mainly methanogens >autotrophic acetogens, when

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Hydrogen production by fermentative consortia

Abstract

Introduction

Section snippets

Hydrogen: a key intermediate in anaerobic environments

Induction of H2 accumulation in anaerobic consortia

Structure, diversity and dynamics of H2-producers communities

Biochemical pathways for H2 production

Hydrogenases

Inhibition of H2 generation by products

Immobilized-cell systems

Conclusions and perspectives

J Biol Chem

Biochim Biophys Acta

Int J Hydrogen Energy

Biochem Biophys Res Commun

Soil Biol Biochem

Int J Hydrogen Energy

J Dairy Sci

Biores Technol

Biores Technol

Int J Hydrogen Energy

FEMS Microbiol Rev

Anaerobe

Int J Hydrogen Energy

Int J Hydrogen Energy

Biochem Biophys Res Commun

Int J Hydrogen Energy

Process Biochem

Water Res

Biores Technol

Int J Hydrogen Energy

Int J Hydrogen Energy

Int J Hydrogen Energy

Process Biochem

Water Res

Biores Technol

Enzyme Microbiol Technol

J Biotechnol

Structure

Int J Hydrogen Energy

Res Microbiol

J Biol Chem

Curr Opinion Microbiol

Int J Hydrogen Energy

Int J Hydrogen Energy

Biores Technol

J Ferment Bioeng

J Ferment Bioeng

J Biosci Bioeng

Int J Hydrogen Energy

Biores Technol

FEMS Microbiol Rev

Int J Hydrogen Energy

Water Res

Phylogenetic identification and in situ detection of individual microbial cells without cultivation

Microbiol Rev

Levels of enzymes involved in acetate, butyrate, acetone and butanol formation by Clostridium acetobutylicum

Eur J Appl Microbiol Biotechnol

Growth kinetics of Acetobacterium sp. on methanol-formate in continuous culture

J Appl Microbiol

Kinetics of hydrogen production with continuous anaerobic cultures utilizing sucrose as the limiting substrate

Appl Microbiol Biotechnol

Acid–base enrichment enhances anaerobic hydrogen production process

Appl Microbiol Biotechnol

Effects of volatile fatty acids on a thermophilic anaerobic hydrogen fermentation process degrading peptone

Water Sci Technol

The capacity of hydrogenotrophic anaerobic bacteria to compete fro traces of hydrogen depends on the redox potential of the terminal electron acceptor

Arch Microbiol

Induction of H₂ accumulation in anaerobic consortia

Structure, diversity and dynamics of H₂-producers communities

Biochemical pathways for H₂ production

Inhibition of H₂ generation by products