Isolation And Identification Of Yeasts In Honey And Their Fermentation Properties

Honey is a natural nourishing food. The low water activity and high osmoticpressure were generally considered not conducive to the existence of microorganisms.But there are still some osmophilic yeasts can tolerate the environment. Yeasts canproduce sugar alcohol in order to adapt to the high osmophilic environment. Sugaralcohol has broad application prospect for its pure sweetness, low calory, goodstability, high tolerance dose and some other properties. In this study, yeasts in honeysamples collected from north of China were isolated and identified. Then theirfermentation properties were studied on screening of sugar alcohol producing yeastsstrains.A total of13samples collected from north of China were used to detect the yeaststrains in the glucose-yeast medium.80yeasts strains were screened. Themorphological, physiological and biochemical properties tests were conducted, aswell as26S rDNA sequence analysis. The results indicated that8osmophilic yeaststrains belong to three speices of four genuses, including2yeast strains ofSchizosaccharomyces octosporus,3yeast strains of Zygosaccharomyces siamensis,2yeast strains of Zygosaccharomyces mellis and1yeast strain of Moniliella pollinis.The8yeast strains were inoculated to30%glucose-yeast medium to cultivate.Three well-growing yeasts were screened from three genuses respectively, whichwere Schizosaccharomyces octosporus A05, Zygosaccharomyces siamensis E17andMoniliella pollinis H10. Then the growth characteristics and fermentation propertiesof the three yeast strains were studied. The results showed that the optimaltemperature of the three yeast strains were30℃, the optimal pH of strain A05andstrain H10were6, the optimal pH of strains E17was5, the optimal sugarconcentration of the three yeast strains were20%, the optimal NaCl concentration ofthe three yeast strains were2%. By TLC and HPLC, the fermentation fluid of strainA05and strain E17mainly contained xylitol and the concentration of xylitol were8.89g/L and2.76g/L. The fermentation fluid of strain H mainly contained erythritoland the concentration of erythritol was11.67g/L.On the basis of decolorization, ion-exchange resin elution, evaporation andcrystallization, xylitol and erythritol were separated and purified. The receiving rate of xylitol of strain A05was57.21%. The receiving rate of xylitol of strain E17was42.16%. And the receiving rate of erythritol of strain H10was64.19%.Finally the melting dynamics of xylitol and erythritol were studied. The resultsindicated that different heating rate had an influence on the thermal stability of xylitoland erythritol. The melting temperature of xylitol was about95~96℃. And themelting temperature of erythritol was about119~120℃.The article mainly studied the isolation and identification of yeasts in honey andscreen xylitol and erythritol producing yeasts strains. Moreover, separation andpurification and melting dynamics of sugar alcohol were studied. The results providereference for the development of sugar alcohol as food additives.