Lignocellulosic hydrogen production using dark fermentation by Clostridium lentocellum strain Cel10 newly isolated from Ailuropoda melanoleuca excrement

Due to the characteristics of renewable and carbon-neutral, lignocellulose is considered to be one of the most potential, feasible, and ample resources for biofuel production on the Earth. However, the low energy conversion capacity of microorganisms is the primary bottleneck for utilizing lignocellulosic biomass to produce biofuel. In the present study, a mesophilic bacterial strain Cel10 identified as Clostridium lentocellum, according to 16S rRNA sequence homology, which can produce hydrogen from lignocellulose was isolated and characterized. The optimal conditions of hydrogen production from carboxymethylcellulose (CMC) are 37 °C, pH 7.0, and 5.0 g L⁻¹. The H₂ production peaked at 5.419 mmol H₂ g⁻¹ CMC under these conditions, which is relatively high compared to the other reported mesophilic bacteria that use cellulose as a substrate. Moreover, the H₂-producing performance of strain Cel10 using cassava residues, a type of natural lignocellulosic feedstock, was also investigated. The results show that the hydrogen production peaked at 4.08 mmol H₂ g⁻¹ after 72 h of incubation, which is almost 1.2-3.8 times higher than the production of other mesophilic and thermophilic strains, while the highest cassava residues degradation rate reached 45.43%. The results validate that Clostridium lentocellum strain Cel10, newly isolated from Ailuropoda melanoleuca excrement, can offer a new method for directly converting lignocellulosic biomass to bio-hydrogen.