Biohydrogen production from various feedstocks by Bacillus firmus NMBL-03

• A newly isolated strain of Bacillus firmus was evaluated for H2 production.
• We used artificial and natural feedstocks as substrates for H2 production.
• The highest VHPR 177.5 ± 7.07 ml/L.h was obtained using starch as substrate.
• The maximum yield was found to be 1.29 ± 0.31 mol H2/mol reducing sugar using sugarcane bagasse hydrolysate as substrate.

In present work our objective was to find out the potential substrates for fermentative hydrogen production using microbial culture of Bacillus firmus NMBL-03 isolated from municipal sludge. A wide variety of substrates (glucose, xylose, arabinose, lactose, sucrose, and starch) and carbohydrate rich waste products (bagasse hydrolysate, molasses, potato peel and cyanobacterial mass) have been used for dark fermentative hydrogen production. All studies were done at optimized physico-chemical conditions. Among all substrates glucose, arabinose, lactose, starch, molasses and bagasse hydrolysate were found to be the favorable substrates for hydrogen production. The highest VHPR i.e. 177.5 ± 7.07 ml/L.h (7.95 ± 0.29 mmol H2/L.h) and maximum H2 production (22.58 ± 2.65 mmol H2/L) was achieved using starch as the substrate. The maximum yield 1.29 ± 0.11 mol H2/mol reducing sugar was obtained from bagasse hydrolysate as substrate. Butyrate and acetate were detected as the end product in all the cases while lactate was also detected from glucose and cyanobacterial hydrolysate. Since considerable amount of H2 also evolved when cyanobacterial mass was used, therefore this microbe can be exploited for hydrogen production through a three stage integrated system. Residual carbohydrate containing biomass left after cyanobacterial H2 production can be utilized in dark fermentative H2 production. Spent media obtained after dark fermentative H2 production contain considerable amount of volatile fatty acids that can be potential substrate for photo fermentative H2 production.