Hydrogen production by Escherichia coli during anaerobic utilization of mixture of lactose and glycerol: Enhanced rate and yield, prolonged production

Abstract

Escherichia coli wild type has the ability to utilize lactose or the mixture of lactose and glycerol producing bio-hydrogen (H2) at different pH values. At pH 7.5 in hyaB (lacking large subunit of hydrogenase (Hyd)-1) and hybC (lacking large subunit of Hyd-2) single mutants fermenting lactose (1 g L−1) H2 yield was ∼7- and 5-fold more, respectively, compared to the wild type. During the fermentation of lactose (1 g L−1) and glycerol (10 g L−1) mixture H2 yield in wild type increased ∼3-fold, compared to fermenting lactose only. H2 generation in wild type was monitored in batch cultures during 168 h of growth when utilizing the mixture of lactose and glycerol in all combinations of different concentration. In hyaB but not in hybC mutant H2 evolution was detected till 240 h in the mixture of 5 g L−1 lactose and 10 g L−1 glycerol. The highest H2 production rate of 21.94 mL L−1 h−1 was detected in hyaB mutant at pH 7.5 when 1 g L−1 lactose was applied. The results showed optimized H2 production using different mutants, lactose and its mixture with glycerol. They can be applied for renewable energy, especially bio-H2 production.