Converting glycerol into hydrogen, ethanol, and diols with a Klebsiella sp. HE1 strain via anaerobic fermentation

An isolated Klebsiella sp. HE1 strain was used to produce H2 and other energy-rich soluble metabolites from glycerol at different pH values, temperatures, and glycerol concentrations. The highest cumulative hydrogen production (6.89 l), H2 production rate (11.76 mmol/h/l), and hydrogen yield (0.345 mol H2/mol glycerol) were obtained at 35 °C, pH 6.0, and an initial glycerol concentration (Cgly) of 50 g/l. These conditions are also preferable for producing ethanol, 1,3-propanediol, and 2,3-butanediol with the highest production rate of 6.80 (Cgly = 50 g/l) mmol/h/l, 6.95 (Cgly = 70 g/l) mmol/h/l and 1.17 (Cgly = 50 g/l) mmol/h/l, respectively, and the highest yields of 0.8 (Cgly = 10 g/l), 0.37 (Cgly = 70 g/l), and 0.08 (Cgly = 70 g/l) mol/mol glycerol, respectively. Combining the gaseous (H2) and liquid fuels (alcohols), the highest total energy generation rate was 26.7 kJ/h/l obtained at Cgly = 70 g/l, while the best total energy yield was 0.90 kJ/kJ at Cgly = 50 g/l.