Abstract:
Continuous, anaerobic fermentations of D-xylose
were performed by Actinobacillus succinogenes 130Z
in a custom, biofilm reactor at dilution rates of 0.05,
0.10 and 0.30 h-1. Succinic acid yields on xylose
(0.55–0.68 g g-1), titres (10.9–29.4 g L-1) and productivities
(1.5–3.4 g L-1 h-1) were lower than those of a
previous study on glucose, but product ratios (succinic
acid/acetic acid = 3.0–5.0 g g-1) and carbohydrate consumption
rates were similar. Also, mass balance closures
on xylose were up to 18.2 % lower than those on glucose.
A modified HPLC method revealed pyruvic acid excretion
at appreciable concentrations (1.2–1.9 g L-1) which
improved the mass balance closure by up to 16.8 %. Furthermore,
redox balances based on the accounted xylose
consumed and the excreted metabolites, indicated an
overproduction of reducing power. The oxidative pentose
phosphate pathway was shown to be a plausible source of
the additional reducing power.
