Effect of pH value on biohydrogen production from cheese whey

Hydrogen production from cheese whey through dark fermentation experiments was investigated in the present study. Two types of cheese whey, namely the effluent from cheese production using a mixture of sheep and cow milk, and the by-product of cow-milk mozzarella production, were the substrates used for the fermentation tests. Either cheese whey only or a mixture of cheese whey and heat-shocked activated sludge were used in mesophilic batch fermentation experiments, where continuous pH control (pH values in the range 5.5-8.5) was adopted. The results of the study indicate that hydrogen production was strongly affected by multiple factors including the type of substrate, the addition of an inoculum, as well as the pH of the digestion system. The mentioned process variables were found to dramatically affect to a varying extent numerous interrelated aspects of the fermentation process, including the hydrogen production potential, the type of fermentation pathways prevailing and the nature and amount of the associated metabolic products, as well as the process kinetics.