Study On Yeasts With Ability Against Osmotic Pressure

While the world is working hard to overcome the problems of globalenvironmental degradation, the greenhouse effect, and the increasingly serious energycrisis, alcohol has been regarded as an environmental-friend and recyclable material, agreen energy. The production and consumption of alcohol as a liquid fuel is becoming adirection of energy development for strategic consideration. At present, its production ismainly based on methods with yeast fermentation. So it is of great significance to screenand breed better yeast strains to perform alcohol industrial production.Some kinds of yeast have ability to live and proliferate in media with high osmoticpressure. These eukaryotic microorganisms are fit well to fermentation processes withhigh-concentration of alcohol. Under high alcohol concentration, the change ofconditions for yeast fermentation might cause a production and accumulation ofglycerol and erythritol. As a result, these yeast strains have a wide range of applicationsand prospects, such as in chemical industry, food industry, pharmaceutical, fermentation,etc. So it needs to study deeply on and develop these yeasts.In this paper, a method combined screening and domesticating on solid media withosmotic pressure gradients was built. By this way, yeast strains were screened fromsamples from soil, fruit, molasses and other selected natural environments. At the end ofscreening, two yeast strains named F-3and F-5were obtained. The identification ofthese two strains was also performed by physiological and biochemical tests,morphology study, fermentation characteristics, and molecular biology ways.Alsocarried out experiments alcohol-resistant yeast and fermentation performancecomparison test, to verify the performance of screening osmophilic yeast.Experiments were taken out by direct screening strains on solid medium with14%of sodium chloride for a osmotic pressure, or domesticating with osmotic pressuregradients. It was found that under high osmotic pressure, a gradient of osmotic pressuredid better for domesticating yeast strains.Results showed that: yeast strains, F-3and F-5, could grow and ferment inenvironment with14%of sodium chloride, with a optimum conditions of pH6.0and30℃. These strains showed a high identity toCandida by ways of molecular biology.