Effect of cornstalk hydrolysis on photo-fermentative hydrogen production by R. capsulatus

Abstract

Cornstalk is a typical cellulose material, which can be used by photo-fermentative H2 production after pretreatment. However, the pretreatment methods have different influence on photo fermentation. In this study, 25.0 g cornstalk was pretreated by HCl/NaOH/cellusase. The hydrolysis rates increased from 45.51% by ddH2O-treatment to 60.79% by diluted HCl-treatment and 51.6% by NaOH-treatment. The corresponding reducing sugar yields were 0.13 g/g, 0.42 g/g and 0.01 g/g, respectively. Enzymatic treatment enhanced the corresponding cornstalk hydrolysis rates to 50.81%, 67.60% and 64.10% with reducing sugar yields of 0.22 g/g, 0.62 g/g and 0.26 g/g. The sorts and concentrations of carbon source for H2 production vary among different hydrolysates. Photo-fermentative H2 production of strain R. capsulatus JL1 and mutant JL1601 (cheR2-) with hydrolysates were investigated. The maximum H2 yield of 123.8 ± 14.2 mL/g by strain JL1 was obtained from alkali-enzyme pretreated cornstalk, while the H2 yield of 224.9 ± 5.2 mL/g by mutant JL1601 (cheR2-) was obtained with acid-enzyme hydrolysate as the substrates. Meanwhile, the alkali pretreated cornstalk was the worst for photo-fermentation of both strain JL1 and mutant JL1601 (cheR2-). Nevertheless, the highest substrate conversion efficiencies for both strains were obtained from ddH2O-pretreated hydrolysate. Two-step pretreated hydrolysates were more beneficial to H2 production for mutant JL1601 (cheR2-) but not for strain JL1.