Transport of glucose in the wine spoilage yeast Dekkera anomala

When grown in media with 0.1 and 2% of glucose Dekkera anomala IGC 5153 pre sented specific, relatively low growth rates and the yield coefficient decr eased from 0.40 to 0.28 g/g as the initial sugar concentration in the mediu m increased. From transport assays carried out in vivo and in vitro, it was observed that the yeast produced two transport systems for glucose which c ould be distinguished by their kinetic parameters and substrate specificity : (i) a high-affinity system able to accept 2-deoxy-D-glucose and D(+)galac tose, and (ii) a low-affinity system able to accept 2-deoxy-D-glucose and D (-)fructose, hut not D(+)galactose. When 2% of glucose or fructose teas use d in the culture medium only the low-affinity carrier was found, while in a cetic acid- or glycerol-grown cells only the high-affinity one was present. If a lower sugar concentration (0.1%, w/v) or ethanol was used in the medi um, both systems were operating. These results suggest that the most probab le mechanism involved in glucose transport by both carriers was a facilitat ed diffusion. The values of the specific glucose transfer rates in cultures with 0.1 and 2% of glucose were very similar to those of the corresponding V-max of glucose transport.