Influence of long-time continuous wine fermentation on morphological changes of yeast immobilized on foam glass

The aim of this work was to study the influence of long-time continuouswine fermentation on yeast morphology. The process of fermentation was carried out in medium of high sugar concentration (about 320 g/dm^), for 3,5months, at 22°C in 4 columns fermentor (4 series). In this experiment, wineyeast Saccharomyces bayanus strain S.O./1AD from the Collection of Pure Culturesof the Department of Food Biotechnology and Microbiology of Warsaw Agriculture University was used. Yeast was immobilized on foam glass. In this study,before and after immobilization (after finished fermentation) the cells were examined by light microscopy, scanning electron microscopy and computer imageanalysis. It was stated that yeast after 3,5 months of continuous fermentationwas bigger and showed morphological and intracellular changes in comparisonwith cells before this process. Before immobilization yeast was ovoid, single orbudding cells. Various shapes of cells were observed after immobilization: elongated, in the shape of “pear”, very big round and “pseudomycelia”. In “pseudomycelium”, the cells remained firmly connected by their cell walls and cytoplasm. In some cells, degeneration of cytoplasmic content was observed, too.These cells contained “granularity”. The results show that long-time, continuous fermentation in high sugar medium causes negative changes ofyeast cells.

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