Fermentative hydrogen production from hydrolyzed cellulosic feedstock prepared with a thermophilic anaerobic bacterial isolate

Abstract

Abstract Hydrogen gas was produced via dark fermentation from natural cellulosic materials and α-cellulose via a two-step process, in which the cellulosic substrates were first hydrolyzed by an isolated cellulolytic bacterium Clostridium strain TCW1, and the resulting hydrolysates were then used as substrate for fermentative H 2 production. The TCW1 strain was able to hydrolyze all the cellulosic materials examined to produce reducing sugars (RS), attaining the best reducing sugar production yield of 0.65 g reducing sugar/g substrate from hydrolysis of α-cellulose. The hydrolysates of those cellulosic materials were successfully converted to H 2 via dark fermentation using seven H 2 -producing bacterial isolates. The bioH 2 production performance was highly dependent on the type of cellulosic feedstock used, the initial reducing sugar concentration ( C RS,o ) (ranging from 0.7 to 4.5 mg/l), as well as the composition of sugar and soluble metabolites present in the cellulosic hydrolysates. It was found that Clostridium butyricum CGS5 displayed the highest H 2 -producing efficiency with a cumulative H 2 production of 270 ml/l from α-cellulose hydrolysate ( C RS,o = 4.52 mg/l) and a H 2 yield of 7.40 mmol/g RS (or 6.66 mmol/g substrate) from napier grass hydrolysate ( C RS,o = 1.22 g/l).