Abstract

The aerobic batch growth of Issatchenkia orientalis DY252 with glucose and fructose medium was investigated at 32 C and pH 5.0. Aerobic ethanol production was evident with yeast I. orientalis. A diauxic lag of about 1 h between growth on glucose and growth on ethanol during batch culture was observed. However, no diauxic growth occurred with fructose. As the incubation temperature was increased from 32 to 39 C, viability at the end of each batch culture declined significantly, from 93 to 43%. Unlike the effect of temperature, viability was not greatly affected by incubation pH, and cell yield values in a range of 0.45-0.48 were obtained. In order to overcome overflow metabolism, a fed-batch culture under glucose limitation was carried out. Compared with aerobic batch culture, about 10% improvement in cell yield was achieved with a fed-batch culture in optimal conditions.

• Keywords: diauxic lag; direct-fed microbials (DFMs); Issatchenkia orientalis; overflow metabolism; viability