Abstract
BackgroundBiological hydrogen production from lignocellulosic biomass shows great potential as a promising alternative to conventional hydrogen production methods, such as electrolysis of water and coal gasification. Currently, most researches on biohydrogen production from lignocellulose concentrate on consolidated bioprocessing, which has the advantages of simpler operation and lower cost over processes featuring dedicated cellulase production. However, the recalcitrance of the lignin structure induces a low cellulase activity, making the carbohydrates in the hetero-matrix more unapproachable. Pretreatment of lignocellulosic biomass is consequently an extremely important step in the commercialization of biohydrogen, and for massive realization of lignocellulosic biomass as alternative fuel feedstock. Thus, development of a pretreatment method which is cost efficient, environmentally benign, and highly efficient for enhanced consolidated bioprocessing of lignocellulosic biomass to hydrogen is essential.ResultsIn this research, fungal pretreatment was adopted for enhanced hydrogen production by consolidated bioprocessing performance. To confirm the fungal pretreatment efficiency, two typical thermochemical pretreatments were also compared side by side. Results showed that the fungal pretreatment was superior to the other pretreatments in terms of high lignin reduction of up to 35.3% with least holocellulose loss (the value was only 9.5%). Microscopic structure observation combined with Fourier transform infrared spectroscopy (FTIR) analysis further demonstrated that the lignin and crystallinity of lignocellulose were decreased with better holocellulose reservation. Upon fungal pretreatment, the hydrogen yield and hydrogen production rate were 6.8 mmol H2 g-1 pretreated substrate and 0.89 mmol L-1 h-1, respectively, which were 2.9 and 4 times higher than the values obtained for the untreated sample.ConclusionsResults revealed that although all pretreatments could contribute to the enhancement of hydrogen production from cornstalk, fungal pretreatment proved to be the optimal method. It is apparent that besides high hydrogen production efficiency, fungal pretreatment also offered several advantages over other pretreatments such as being environmentally benign and energy efficient. This pretreatment method thus has great potential for application in consolidated bioprocessing performance of hydrogen production.
Highlights
Biological hydrogen production from lignocellulosic biomass shows great potential as a promising alternative to conventional hydrogen production methods, such as electrolysis of water and coal gasification
An appropriate pretreatment is desired so that lignin is degraded to the maximum while cellulose and hemicellulose are still retained [21,22,23]
In order to evaluate the feasibility of P. chrysosporium pretreatment for cornstalk prior to fermentation, the chemical compositions of cornstalk after fungal pretreatment were compared with other two typically thermochemical pretreatments
Summary
Biological hydrogen production from lignocellulosic biomass shows great potential as a promising alternative to conventional hydrogen production methods, such as electrolysis of water and coal gasification. Biological conversion of lignocellulosic biomass into H2 commonly involves i) pretreatment of lignocelluloses, ii) hydrolysis of polysaccharide constituents into reducing sugars with a cellulolytic enzyme cocktail, and iii) fermentation of sugars with H2-producing microorganisms These processes were carried out at different reactors, or by different microorganisms separately [5]. An alternative approach known as consolidated bioprocessing (CBP), which could combine enzyme production, saccharification, and H2 fermentation in a single step was developed. This integrated process configuration is more favorable for cellulosic H2 production due to its simple operating process, low capital and substrate cost, short processing time, high H2 yields, and low contamination risk [6,7,8,9]. CBP is regarded as the optimal industrial configuration to produce H2
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