H2 production by Escherichia coli batch cultures during utilization of acetate and mixture of glycerol and acetate

Abstract

Escherichia coli produces molecular hydrogen (H2) from different carbon substrates like sugars, glycerol and some organic acids during mixed-acid fermentation. H2 production in batch cultures during acetate utilization of different concentrations (1 g L−1–5 g L−1 was used) was investigated at different pHs. H2 yield in E. coli wild type cells was highest at the log growth phase in the presence of 5 g L−1 acetate. Either at pH 7.5 or pH 6.5 H2 yield was 5.07 mmol L−1. At pH 5.5, H2 production was detected when 1 g L−1acetate was supplemented in the growth medium. Interestingly, in the presence of 1 g L−1 acetate H2 yield was highest at pH 6.5 compared to 2 and 5 g L−1 concentrations. As acetic acid and glycerol are unavoidable constituents of various industrial or agricultural wastes, H2 generation using the mixture of acetate (5 g L−1) and glycerol (10 g L−1) at different pHs was also investigated. The highest H2 yield of 5.16 mmol L−1 was detected at the log growth phase at pH 7.5. H2 generation was continuously detected at pH 7.5 and pH 5.5 for 96 h of growth. These data can be applied to further enhancement of H2 energy production biotechnology and to use different industrial or agricultural wastes where acetate and/or glycerol is present to produce H2.