Effect of osmotic potential of sodium chloride on the biological activity of yeast isolated from some foodstuffs.

摘要

A total of 39 osmophilic yeasts were isolated from grapes, figs, guavas, apple jam, honey, sugarcane juice, sugar syrup, high-test molasses and tomato juice. The isolates were assigned to the yeast genera Torulopsis, Saccharomyces, Candida or Rhodotorula, based on their morphological and physiological characteristics. Cane juice yielded an isolate of S. cerevisiae; sugar syrup, a Candida parapsilosa; high-test molasses, 11 isolates of Torulopsis species; honey, one S. rouxii and 11 of Torulopsis. The effects of different NaCl concentrations on the biological activity of Saccharomyces kluyveri G29, S. cerevisiae S41 and Rhodotorula mucilaginosa [R. rubra] J38 were evaluated during batch culture in shake flasks. The 2 Saccharomyces species toleratedup to 10% NaCl, while R. rubra J38 grew in 15% NaCl. In media containing 10% NaCl, net biomass and biomass yield coefficient decreased as initial glucose concentration increased, reaching minima at 20% glucose for S. kluyveri G29 or 40% for S. cerevisiae S41 or R. rubra J38. The greatest amount of glycerol was produced by Saccharomyces strains at 20% glucose. Rates of ethanol and glycerol production were higher in media containing glucose alone than in those containing glucose and NaCl. S. kluyveri G29was more sensitive than S. cerevisiae S41, in terms of growth and ethanol or glycerol production in the presence of glucose and NaCl.