Hydrogen production by Escherichia coli Δ hycA Δ lacI using cheese whey as substrate

Abstract

This study reports a fermentative hydrogen production by Escherichia coli using cheese whey as substrate. To improve the biohydrogen production, an E. coli ΔhycA Δ lacI strain (WDHL) was constructed. The absence of hycA and lacI genes had a positive effect on the biohydrogen production. The strain produced 22% more biohydrogen in a shorter time than the wild-type (WT) strain. A Box-Behnken experimental design was used to optimize pH, temperature and substrate concentration. The optimal initial conditions for biohydrogen production by WDHL strain were pH 7.5, 37 °C and 20 g/L of cheese whey. The specific production rate was improved from 3.29 mL H 2/optical density at 600 nm (OD 600nm) unit-h produced by WDHL under non-optimal conditions to 5.88 mL H 2/OD 600nm unit-h under optimal conditions. Using optimal initial conditions, galactose can be metabolized by WDHL strain. The maximum yield obtained was 2.74 mol H 2/mol lactose consumed, which is comparable with the yield reached in other hydrogen production processes with Clostridium sp. or mixed cultures.