Effect of pH on glucose and starch fermentation in batch and sequenced-batch mode with a recently isolated strain of hydrogen-producing Clostridium butyricum CWBI1009

This paper reports investigations carried out to determine the optimum culture conditions for
the production of hydrogen with a recently isolated strain Clostridium butyricum CWBI1009.
The production rates and yields were investigated at 30 °C in a 2.3 l bioreactor operated in
batch and sequenced-batch mode using glucose and starch as substrates. In order to study the
precise effect of a stable pH on hydrogen production, and the metabolite pathway involved,
cultures were conducted with pH controlled at different levels ranging from 4.7 to 7.3
(maximum range of 0.15 pH unit around the pH level). For glucose the maximum yield (1.7
mol H2 mol-1 glucose) was measured when the pH was maintained at 5.2. The acetate and
butyrate yields were 0.35 mol acetate mol-1 glucose and 0.6 mol butyrate mol-1 glucose. For
starch a maximum yield of 2.0 mol H2 mol-1 hexose, and a maximum production rate of 15
mol H2 mol-1 hexose h-1 were obtained at pH 5.6 when the acetate and butyrate yields were
0.47 mol acetate mol-1 hexose and 0.67 mol butyrate mol-1 hexose.