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The cloning and sequencing of the Kluyveromyces lactis gene encoding triose phosphate isomerase activity (TIM) are described. The K lactic mutant strain, unlike Saccharomyces cerevisiae, was observed to have the ability to grow on glucose. Results of preliminary experiments of bioconversion suggest that, similar to the S cerevisiae TIM-deficient strain, the K lactis TIM-deficient strain is able to produce glycerol with high yield.

The development of a homolactic Kluyveromyces lactis yeast strain, which displays high concentration and high productivity of lactic acid at a pH level below 5 to 5.5, the typical minimum pH range for lactate production by conventional microbial cells, is reported. Results represent the first example of a total replacement of a fermentation product mediated by metabolic engineering methods in yeast genera.

Yest divides through an asymmetrical process. A series of experiments was used to analyze the Po value and the duration of the budded phase in an asynchronously growing Saccharomyces cerevisiae population using a newly developed flow cytometric approach. Results derived during transient states of growth show that the whole population requires a few hours to reach a balanced growth condition. Effects of nutritional shift-down were also determined.

Researchers have been able to increase the secretion of human insulin-like growth hormone from yeast by fusing the hIGF-1 gene to the prepro-alpha-factor leader sequence and inactivating the GAS1 gene of the yeast. This hormone is of interest to the pharmaceutical industry.

Despite the importance of some Zygosaccharomyces species as agents causing spoilage of food, the carbon and energy metabolism of most of them is yet largely unknown. This is the case with Zygosaccharomyces bailii. In this study the occurrence of the Crabtree effect in the petite-negative yeast Z. bailii ATCC 36947 was investigated. In this yeast the aerobic ethanol production is strictly dependent on the carbon source utilised. In glucose-limited continuous cultures a very low level of ethanol was produced. In fructose-limited continuous cultures ethanol was produced at a higher level and its production increased with the dilution rate. As a consequence, on fructose the onset of respiro-fermentative metabolism caused a reduction in biomass yield. An immediate aerobic alcoholic fermentation in Z. bailii was observed during the transition from sugar limitation to sugar excess, both on glucose and on fructose. The analysis of some key enzymes of the fermentative metabolism showed a high level of acetyl-CoA synthetase in Z. bailii growing on fructose. At high dilution rates, the activities of glucose- and fructose-phosphorylating enzymes, as well as of pyruvate decarboxylase and alcohol dehydrogenase, were higher in cells during growth on fructose than on glucose. [Copyright &y& Elsevier]