Production of L-phenylacetyl carbinol by immobilized yeast cells: II. Semicontinuous fermentation

The cyclic, semicontinuous production of L-phenylacetyl carbinol (L-PAC) from a benzaldehyde substrate by Saccharomyces cerevisiae ATCC 834 immobilized in calcium alginate beads was substantially enhanced to about 4.5 g/L in a second cycle by reactivation in fresh medium for 24 h, following an earlier 24-h period of production from substrate. Intermittent feeding of benzaldehyde was employed (four doses in 3 h). In subsequent similar cycles, however, the production returned to that produced in the first cycle, viz. L-PAC concentration of 2-3 g/L in the medium. Production of L-PAC was also increased by adaptation of the cells over 200 h of exposure to the benzaldehyde substrate (compared to wild-type cells) and by continuous (as compared to intermittent) feeding of the substrate. A liter as great as 10 g/L was obtained with wild-type cells by continuous feeding of benzaldehyde over 6 h. Immobilization not only protected the cells from toxic effects of substrate but also permitted them to be used during 7 cycles of semicontinuous operation over more than 200 h.