GROWTH OF SCHIZOSACCHAROMYCES-POMBE ON GLUCOSE-MALATE MIXTURES IN CONTINUOUS CELL-RECYCLE CULTURES - KINETICS OF SUBSTRATE UTILIZATION

The aerobic growth of Schizosaccharomyces pombe on mixtures of glucose and malate was investigated during continuous high cell density cultu res with partial cell-recycle using a membrane bioreactor. Determinati on of the specific metabolic rates relative to substrates and products allowed the capacity of the yeast to metabolize malic acid under both oxidative metabolism (carbon limited cultures) and oxidofermentative metabolism (carbon sufficient cultures) situations to be characterized . Under carbon limiting conditions, the specific rate of malate utiliz ation was dependent on the residual concentration and a limit for a pu rely oxidative breakdown without ethanol formation was observed for a characteristic ratio between the rates of substrate consumption q(M)/q (G) of 1.63 g.g(-1). In addition, the mass balance analysis revealed t he incorporation of malic acid into biomass. In carbon excess environm ents, the specific rate of malate utilization was dependent on both th e residual malate and the specific rate of glucose consumption indicat ing that in addition to its conversion into ethanol malate can be resp iratively metabolized for q(M)/q(G) ratios higher than 0.4 g.g(-1).