Growth and product formation by C. celer in pH-controlled batch fermentations performed at pH 7 and 6, with and without N
sparging. Growth (A), glucose consumption (B) and end product accumulation (C-F) profiles of C. celer cultured with 10 g/l glucose at pH 7 (straight lines) with N2 sparging (Case I, filled squares) and without N2 sparging (Case II, filled circles), and at pH 6 (dashed lines) with N2 sparging (Case III, open squares) and without N2 sparging (Case IV, open circles). Larger symbols in panel A represent sampling points for ATP, NADH and NAD+ measurements. Data are from one representative fermentation per condition.