The use of monochloroacetic acid for improved ethanol production by immobilized Saccharomyces cerevisiae

Saccharomyces cerevisiae adsorbed on acid-treated glass beads produced 5.4 g l-1 ethanol at 96 h in batch process. Precoating the acid-treated glass beads with gelatin (25 g l-1) before immobilization of the cells increased ethanol production to 26.3 g l-1 at 72 h. Cell leakage into the medium was decreased when the immobilized cells were cross-linked with increasing concentrations of glutaraldehyde (0100 g l-1). Although monochloroacetic acid inhibited ethanol production and cell multiplication at concentrations greater than 0.1 g l-1, at a concentration of 0.01 g l-1 it not only increased the ethanol production to 52.1 g l-1 but also shortened the ethanol production time to 48 h. In a semi-continuous batch process with the feed containing 0.01 g l-1 monochloroacetic acid, immobilized cells showed no significant change in ethanol-producing ability for 40 days when incubated with nutrient medium intermittently.