Exploitation of defined bacterial cultures for production of hydrogen and polyhydroxybutyrate from pea-shells

Biological hydrogen (H2) and polyhydroxybutyrate (PHB) production from biowaste as feed were investigated with different bacteria. The 23 bacterial strains used in different combinations belonged to - Bacillus spp., Bordetella avium, Enterobacter aerogenes, Proteus mirabilis and a marine bacterium. Defined mixed H2-producers alone could evolve 140–145 mL H2 from 250 mL PSS (Pea-shells slurry). PSS hydrolysed with defined hydrolytic bacterial mixture followed by H2-producers resulted in the production of 5.2 L H2 from 4 L PSS. It was equivalent to a yield of 65 L H2 kg−1 TS fed. Here, H2 constituted 55.2% of the total biogas. On the other hand, Bacillus cereus EGU44 could produce 1685 mg PHB L−1 from prehydrolyzed PSS, which was equivalent to 62.5 g kg−1 TS fed. This is first report of its kind on the use of defined bacterial cultures for each of these steps. This approach of using defined mixed cultures is expected to enhance the sustainability of the process by enhancing their chances of survival in comparison to single bacterial culture. The use of biowaste as feed can further improve the economics of the process.

► Fermentation of biowaste into hydrogen (H2) and polyhydroxybutyrate (PHB) using defined bacterial cultures for each stage.
► Combination of bacterial cultures for hydrolysis of biowaste along with H2 producers increased H2 production by 1.89 fold.
► A 2.87 fold enhancement in PHB production by Bacillus strains from peashells as sole feed.
► Pea-shells as feed produced 65 L H2 kg-1 and 62.5 g PHB kg-1 TS fed.