###### Abstract  
Screening new _Clostridium_ strains that can efficiently utilize lignocellulosicose 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 \(\pm\) 4.8 mL/g and 7.7 \(\pm\) 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, endoplasmic, \(\beta\)-glucosidase and xylanase produced by _Clostridium populeti_ FZ10. The maximum hydrogen yield and hydrogen production rate from CS were 92.5 \(\pm\) 3.7 mL/g and 5.9 \(\pm\) 0.2 mL-g\({}^{-1}\)-h\({}^{-1}\),respectively, with a cellulose degradation of 47.2 \(\pm\) 2.3% and a hemicellulose degradation of 58.1 \(\pm\) 2.0%. This study demonstrates that _Clostridium populeti_ FZ10 is an ideal candidate for directly converting lignocellulosicose into bihydrogen under mesophilic conditions. The discovery of strain _C. populeti_ FZ10 has special significance in the field of bioenergy. Clostitrium populeti FZ10; isolation and identification; dark fermentation; hydrogen production; lignocellulosicose +
Footnote †: journal: Applied Sciences  
Undoubtedly, these processes will lead to higher costs and block the commercialization of hydrogen production from cellulose-based biomass. Microorganisms play a pivotal role in the hydrogen fermentation system. During the hydrogen fermentation process, specific microbes could produce enzymes such as endoglucanase, exoglucanase, cellobiohydrolase, xylanase, \(\beta\)-xylosidases, etc., which are responsible for complex substrate hydrolysis and converting hydrolyses into biohydroogen [12; 13; 14]. This integrated process is more economical for hydrogen production from lignocellulosic [15]. As a proficient hydrogen producer, the genus _Clostidium_ has been widely researched in dark fermentative hydrogen production because of its high hydrogen productivity, wide range of substrate utilization and high resistance to adverse conditions [16; 17; 18]. Moreover, the _Clostidium_ species is usually the dominant hydrogen-producing genus which exists in anaerobic mixed cultures [19]. Some species of _Clostidium_ were found to be capable of producing hydrogen from cellulosic substrates [20; 21; 22; 23]. However, most _Clostidium_ species seem to prefer oligosaccharides for hydrogen production rather than lignocellulosic, and several disadvantages such as a low hydrogen yield and substrate conversion efficiency limit their application. [PERSON] et al. isolated a mesophilic _Clostidium_ which could effectively utilize sucrose and xylose to produce hydrogen, and the hydrogen yield reached 129.1 mL/g and 172.9 mL/g, respectively; however, the strain could not directly utilize cellulose to produce hydrogen [24]. [PERSON] et al. found a thermophilic _Clostidium_ that also faced the same problem of low hydrogen yield from cellulosic biomasses. The maximum hydrogen yield of this strain from grain was only 23.97 mL/g [25]. Ferrentative hydrogen production using lignocellulosic as a substrate can effectively reduce the production cost. This will lead to the further development of hydrogen production from renewable resources. Although much work has been undertaken to obtain hydrogen from dark fermentation processes, the hydrogen yield produced by the _Clostidium_ species from cellulosic-based biomasses is still considered to be insufficiently high. In view of this point, screening new _Clostidium_ strains that can efficiently utilize natural lignocellulosic to produce hydrogen is of value.