Whole cell of pure Clostridium butyricum CBT-1 from anaerobic bioreactor effectively hydrolyzes agro-food waste into biohydrogen.

Abstract

Recycling organic waste and converting them into renewable energy are a promising route for environment protection and effective biochemical reactions suitable for industrial hydrogen synthesis. This study targeted to isolate a pure anaerobic culture with potential to hydrolyze different biomass and production of biohydrogen. For this, a sample of full-scale anaerobic digester, fed with a multicomponent solid, was inoculated on Reinforced Clostridial Medium (RCM) in strict anaerobic conditions. An anaerobic Clostridium butyricum CBT-1 strain was isolated, identified from morphological and 16S rRNA sequence. The CBT-1 culture expressed amylase, cellulase and peroxidases activities. The strain exhibited visual decolorization of both Azure B and crystal violet dyes. In batch fermentation experiment, the CBT-1 produced highest of 3.06, 2.67 and 2.46 mol/mol H2 yield from glucose, starch and cellulose respectively, whereas, the CBT-1 showed low 0.43 mol H2/mol of substrate from untreated rice straw due to lignin in compact structure and comparatively high H2 yield of 1.91 and 2.01 mol H2/mol of substrate rice straw hydrolysate and kitchen food waste (KFWS) respectively. The cumulative volumetric yield of H2 was 358.15, 300.8 and 294.5NmL/gSub from glucose, starch and cellulose respectively. Similarly, the cumulative H2 volume was 76.7, 184.4, 237.2 NmL/gVS from untreated rice straw, rice straw hydrolysate and kitchen food waste. This study emphasizes the prospects to find similar robust anaerobic culture for hydrolyzing complex biomass. Such strains could be used as standard co-inoculum for biohydrogen obtaining and as the biocatalyst for commercial scale applications.