Continuous culture for the bioproduction of glycerol and ethanol by Hansenula anomala growing under salt stress conditions.
Résumé
Continuous cultures of Hansenula anomala were carried out in media at low water activity, resulting from NaCl addition. Three dilution rates were compared and it was shown that a clear steady state was only recorded for the lowest dilution rate tested (0.03 h−1), leading to a biomass concentration of 4.3 g L−1. At 0.06 h−1 dilution rate, steady state was maintained for no more than 20 h and a clear wash-out was observed at 0.12 h−1. The experimental ratio ethanol on glycerol produced at steady state (D = 0.03 h−1) was similar to that previously recorded in batch culture in similar conditions after 30 h of growth, 7.8 and 7.9, respectively. The comparison of continuous culture to repeated batch culture was clearly in favour of the continuous culture, which led to significantly higher glycerol and ethanol production rates, 4.5 and 4 times higher than those recorded in repeated batch culture, respectively, even if significant amounts of glucose remained in the bleeding of the bioreactor.