Sequential Dark-Photo Batch Fermentation and Kinetic Modelling for Biohydrogen Production Using Cheese Whey as a Feedstock.

The present work describes the utilisation of cheese whey to produce biohydrogen by sequential dark-photo fermentation. In first stage, cheese whey was fermented by Enterobacter aerogenes 2822 cells in a 2 L double-walled cylindrical bioreactor to produce hydrogen/organic acids giving maximum biohydrogen yield and cumulative hydrogen of 2.43 ± 0.12 mol mol-1 lactose and 3270 ± 143.5 mL at cheese whey concentration of 105 mM lactose L-1. The soluble metabolites of dark fermentation when utilised as carbon source for photo fermentation by Rhodobacter sphaeroides O.U.001, the yield, and cumulative hydrogen was increased to 4.22 ± 0.20 mol mol-1 VFA and 3800 ± 170 mL, respectively. Meanwhile, an overall COD removal of about 38.08% was also achieved. The overall biohydrogen yield was increased from 2.43 (dark fermentation) to 6.65 ± 0.25 mol mol-1 lactose. Similarly, the modelling for biohydrogen production in bioreactor was done using modified Gompertz equation and Leudeking-Piret model, which gave adequate simulated fitting with the experimental values. The carbon material balance showed that acetic acid, lactic acid, and CO2 along with microbial biomass were the main by-products of dark fermentation and comprised more than 75% of carbon consumed.