Screening new Clostridium strains that can efficiently utilize lignocellulose to produce hydrogen is extremely important for dark fermentative hydrogen production. In this study, a mesophilic hydrogen-producing bacterium, identified as Clostridium populeti FZ10, was newly isolated from compost acclimated by microcrystalline cellulose. The strain could produce hydrogen from various cellulosic substrates. The performances of hydrogen production from microcrystalline cellulose (MCC) and corn stalk (CS) were especially investigated. The maximum hydrogen yield and hydrogen production rate from MCC were 177.5 ± 4.8 mL/g and 7.7 ± 0.2 mL·g⁻¹·h⁻¹, respectively. Furthermore, scanning electron microscopy (SEM) images showed that the structure of CS was destroyed after fermentation, which could be attributed to the presence of exoglucanase, endoglucanase, β-glucosidase and xylanase produced by Clostridium populeti FZ10. The maximum hydrogen yield and hydrogen production rate from CS were 92.5 ± 3.7 mL/g and 5.9 ± 0.2 mL·g⁻¹·h⁻¹,respectively, with a cellulose degradation of 47.2 ± 2.3% and a hemicellulose degradation of 58.1 ± 2.0%. This study demonstrates that Clostridium populeti FZ10 is an ideal candidate for directly converting lignocellulose into biohydrogen under mesophilic conditions. The discovery of strain C. populeti FZ10 has special significance in the field of bioenergy.

This study investigated the feasibility of producing L-lactic acid (LA) from dry corn stalk (DCS) that was pretreated by ensiling by an anaerobic microbial community consisting of Bacillus coagulans, Lactobacillus fermentum, and Enterococcus durans. After 28 days of ensiling, the LA and acetic acid content in the microsilage was 2.04 ± 0.08% and 0.38 ± 0.01%, respectively, and the pH was 4.47 ± 0.13. Enterococcus and Lactobacillus became the dominant microbiota during the ensiling process. Twenty-eight-day-old microsilage was then subjected to fermentation by B. coagulans to produce LA in a simultaneous saccharification and co-fermentation process. The enzymatic hydrolysis yield reached >96%. The maximal concentration of LA reached 18.54 ± 0.52 g/L with a substrate concentration of 5%, where the yield of LA was 0.31 ± 0.01 g/g DCS and the optical purity of the product LA was >97%. Anaerobic ensiling is viable for the pretreatment of biomass for the production of value-added chemicals.

Cellulase adsorption of lignocellulosic materials is the key link during enzymatic hydrolysis. Hot-washing process (above lignin glass transition temperature) was used to change the physical structure of lignin, decrease covalent connection between cellulose and lignin, reduce the concentration of inhibitor, and explore the feasibility of enzymatic hydrolysis. The general objective of the paper was conducted to determine whether the hot-washing process has the potential to change the mechanism of lignin on enzyme hydrolysis. Hot-washing was carried out at 151 °C for 20 min. The ratio of acid insoluble lignin to acid soluble lignin was increased, while the formation of spherical lignin droplets on the cell wall surface was decreased. Enzymatic digestibility of hot-washed filter cakes showed enhanced digestibility over the control samples. The concentration of fermentation inhibitor (acetic acid, formic acid, furfural and 5-hydroxymethylfurfural) obviously decreased after hot-washing process. Hot-washing process significantly increased the adsorption ability of cellulase on the substrates and digestibility of biomass without removing much of the insoluble lignin content. Lignin distribution and/or physical property composition play a role.