The ogd1 and kgd1 mutants lacking 2-oxoglutarate dehydrogenase activity in yeast are allelic and can be differentiated by the cloned amber suppressor

Properties of hydrogel materials used for entrapment of microbial cells in production of fermented beverages

Approaches using immobilized biological materials are very promising for application in different branches of the food industry, especially in the production of fermented beverages. Materials tested by our team for the process of entrapment belong to the family of charged polysaccharides able to form beaded hydrogels by ionotropic gelation (e.g. alginate, pectate, kappa-carrageenan) and synthetic polymers (e.g. polyvinyl alcohol) forming bead- and lens-shaped hydrogels by thermal sol/gel transition. Concentration of a gel, conditions and instrumentation of gelation process, bead and size distribution, porosity, diffusion properties, mechanical, storage and operational stability, and many other parameters were followed and optimized. Our work has been oriented especially to practical applications of immobilized cells. Brewing yeast cells were successfully immobilized by entrapment materials and used in a process of batch and continual production of beer, including primary and secondary fermentation of wort. Other applications include continual production of ethanol by fermentation of different saccharide substrates (molasses, glucose syrup, wheat hydrolysate), mead and non-alcoholic beverages production.

The properties of the multicopy suppressor of the ogd1 mutation in yeast

The 8.1 kb chromosomal fragment partially suppressing the ogd1 mutation in Saccharomyces cerevisiae has been cloned. The molecular analysis revealed that its suppressor gene codes for a natural glutamine tRNA(CAG) and maps on chromosome XIII in the upstream region of the URA10 gene. The multicopy plasmids containing this tRNA gene also suppressed the standard trp1-1 amber mutation and conferred the sensitivity of yeast cells to paromomycin and increased temperature.