Improving photofermentative hydrogen productivity of photosynthetic bacteria using a formulated Fe and Mo metal supplemented lignocellulosic substrate

Abstract

Strategy to improve single-stage photofermentative hydrogen productivity of photosynthetic bacteria (PSB) by efficient use a formulated lignocellulosic substrate through suitable supplement of iron and molybdenum as enhancers of microbial activity of R. palustris was proposed. The maximum hydrogen production rate of 48.1 ml h−1 L−1 was obtained using response surface methodology as the result of accelerated bioreaction of proton reduction under inoculum density of 118.1 mg L−1, Fe2+ of 13.2 mg L−1 and Mo6+ of 2.65 μg L−1. Biokinetic analysis revealed the enhanced microbial activities in biomass synthesis and H2 production. Suitable metal addition enabled PSB to act in whole as biocatalyst to facilitate assimilation of the formulated electron-rich carbon source from wheat straw through the efficient electron transfer needed for both cell growth and enzyme function of nitrogenase. Therefore, higher kinetic values of kc in 0.146 h−1 and Rm in 59.4 ml h−1 L−1, accompanied with improved performances of H2 yield in 1.56 mol mol−1 carbon and substrate degradation in 93.6% were attained.