Influence of stock and modified culture media on biohydrogen production through photo-fermentation of distillery biowaste effluent using purple-non sulphur bacterium

Abstract

Biohydrogen from biological wastes offers clean energy, while distillery by-products cause environmental degradation when discharged. The novelty of this research lies in the development of specialized culture media, distinct from conventional stock media, for the photofermentation of distillery biowaste effluent (DBE) substrates to enhance biohydrogen production by utilizing Rhodopseudomonas pseudopalustris, a purple non-sulphur bacterium. This study explores the intricate interplay between acetate, phosphate nutrient supplements, and gas space concentrations to identify the most effective conditions for hydrogen accumulation. The investigation revealed that the highest biomass concentration of 1.2 g/L was achieved with 5 g/L Ca, doubling over the 10-day cycle from the initial inoculum density of 0.5OD at 600 nm. As the biomass concentration increased, the hydrogen produced increased steadily till the threshold of mass transfer. Moreover, peak hydrogen production of 200 ml H2/L occurred at 3 g/L acetate, with no significant difference at 5 g/L. Modified Rhodospirillaceae medium (DCM) produced more hydrogen (150 ml H2/L) than standard Rhodospirillaceae medium (RhM) due to its higher phosphate and molybdenum content. Under conditions of phototrophy, anoxia, and nitrogen limitation, R. pseudopalustris produced hydrogen of up to 170 ml H2/L. DBE addition increased hydrogen production, with diluted & modified Rhodospirillaceae medium (DCMd) & diluted Rhodospirillaceae medium (RhMd) producing 24 % and 78 % more hydrogen respectively, than the stock media. Furthermore, the finest synergistic combination of acetate and phosphate concentrations (5 g/L and 1 g/L), novel RhMd media, with nitrogen in the gas space, resulted in the highest hydrogen accumulation of 278 ml H2/L.