CARBON AND ENERGY BALANCES IN CELL-RECYCLE CULTURES OF SCHIZOSACCHAROMYCES-POMBE

A strain of the fission yeast Schizosaccharomyces pombe was aerobicall y grown in a cell-recycle fermentor under various operating conditions , i.e., different bleeding rates and various separate feed rates of gl ucose and basal medium. Carbon and energy balances were analyzed durin g steady-state culture regimes, allowing growth yields and maintenance coefficients to be determined under glucose-limited and glucose-exces s environments. Special attention was given to the metabolic shift fro m purely oxidative to respirofermentative glucose catabolism resulting from a change in the growth-limiting factor. No maintenance requireme nts for the carbon source and for energy were observed during glucose- limited culture regimes and oxidative catabolism. Under glucose excess and respirofermentative metabolism, the m(G) coefficient was shown to be growth-linked, whereas the enhancement of the apparent m(e) coeffi cient observed for increased residual glucose concentrations could be assigned to a decline in the ATP yield. (C) 1993 John Wiley & Sons, In c.