Scale up of the production of xylitol dehydrogenase and alcohol dehydrogenase from Pachysolen tannophilus grown on xylose

Abstract

Coproduction of two enzymes, xylitol dehydrogenase (XDH) and alcohol dehydrogenase (ADH), was attempted using the yeast Pachysolen tannophilus. Production of both enzymes was scaled up to a volume of 500 l with the yeast growing on xylose a the sole carbon source. Maximal amount of XDH was obtained by harvesting the cells at the end of the logarithmic growth phase. Activity of XDH was induced by imposing anaerobic conditions, thereby yielding 10 times more enzyme than was obtained for aerobic growth conditions. In crude extracts, obtained by passage through a French press (20 000 p.s.i.), XDH activity was 0.057 u/mg protein and ADH was 0.15 u/mg for aerobic growth and 1.5 u/mg for microaerophilic growth. Extraction of intracellular enzymes on a large sale was performed with a combination of cell wall lytic enzymes and an industrial homogenizer (Manton-Gaulin, 3000 p.s.i.). This system enabled a continuous mode of operation (single passage through homogenizer) with a high cell density (100 g/l) and the extracts contained 0.033 u/mg of XDH and 0.45 u/mg protein of ADH.