Ecobiotechnological Approaches: Enrichment Strategy for Improvement of H2 Production

Abstract

Hydrogen has been mooted as future fuel on the basis of its carbon neutrality, renewable nature, and highest energy density. In the recent times, its economical production has gained attention. The present chapter deals with a comprehensive insight on dark-fermentative biohydrogen production process. This process is less energy intensive and environmentally benign, and waste materials can be used as substrate. Biochemical insight on hydrogen production via dark fermentation exemplifies the complexity of the process. The maximum H2 yield of 4 mol H2 per mol of glucose has been observed when fermentation followed a solely acetate pathway. The potential H2-producing microorganisms are present in various natural and man-made habitats such as sewage sludge, anaerobically digested sludge, animal waste, compost, hot springs, oceanic sediments, and soil. There are many advantages of working with mixed consortia, viz., presence of different hydrolytic enzymes, better oxygen tolerance, etc. Various pretreatment processes have been explored to enrich H2-producing microbes. A detailed pretreatment processes, viz., chemical, physical, combined treatments, etc., creates a selection pressure, which could effectively alter the microbial dynamics of the mixed culture. Molecular techniques like polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), terminal restriction fragment length polymorphism (T-RFLP), ribosomal intergenic spacer analysis (RISA), quantitative PCR (qPCR), single-strand conformation polymorphism (SSCP), fluorescence in situ hybridization (FISH), and fluorescence-activated cell sorting (FACS) could be used for advanced and rapid microbial characterization. Use of cheap, renewable, and easily available raw materials could bring down the production cost of bioH2.