Screening Of Yeast Strains And Fermentation Conditions For Hight Yield Production Of D-arabitol

D-arabitol receives people's attention as intermediates of xylitol fermentation, which can't be replaced. The objective of this work was to select a strain which bad the ability of fermentation of glucose into D-arabitol. It discussed primary factor of D-arabitol fermentation. Batch fermentation and fed batch fermentation were studied. It was basic work as the D-arabitol industrial production in the future. The mainly researching contents are blow.The method for the analysis and determination glucose and D-arabitol in the first screening of strains was studied. With paper chromatography, the substrate and the product were separation successful. According to the different transport ratio of glucose and D-arabitol in developing solvent, the fermentation fluid contained D-arabitol or not. The high performance liquid chromatography could precise determination the products and substrate. The analysis method provided the good instruction for the D-arabitol fermentation from glucose.One yeast strain, which was isolated from 378 osmophilic yeasts, was found to be able to utilize D-glucose effectively. The concentration of D-arabitol is 73.82g/L, and the substrate conversion rate of glucose is 36.91%. On the basis of assimilation physiological tests and Molecular biology teast, all of the detection led to the identification of yeast strain as a strain of Debaryomyces hansenii. GenBank accession number of ITS nucleotide sequence was EF196809. The strain was submitted to the Culture and Information Centre of Industrial Microorganisms of China Universities and the corresponding serial number was CICIM Y 0504.The Debaryomyces hansenii obtained was taken as the further research strain. In the result of this research, it discussed seed, substrate glucose, nitrogen source, yeast extract, initial pH of culture medium, temperature and liquid volume and so on to D-arabitol fermentation influence, finally indicated that yeast extract in the culture mediumas and the dissolves oxygen had important influence for D-arabitol fermentation. Simultaneously the excessive nitrogen source in the culture medium does not favor the synthesis of D-arabitol. The initial pH of culture medium under the acidic condition favors the growth of yeast and the product synthesis. Through researching the culture medium and the condition, the culture medium and the condition are: 200g/L glucose, 2g/L urea, 3g/L potassium dihydrogen phosphate, 2.5g/L seven water magnesium sulfate, 10g/L yeast paste, initial pH 3, media volume 20 mL, 30℃, 150r/min and the vaccination quantity is 5%.The product D-arabitol concentration is 105.41g/L in 120hours under the best fermentation condition, and the substrate conversion rate of glucose is 52.7%. Compares to screening, the D-arabitol concentration enhanced 30g/L and the substrate conversion rate enhanced 42.8%.Based on the above optimum condition, the fermentation enlargement was performed with strain Debaryomyces hansenii in 15-liter fermentor. Batch fermentation and fed batch fermentation were studied. The result showed that the concentration of D-arabitol was 64.09g/L and the substrate conversion rate was 33.9% in the batch fermentation. In the fed batch fermentation the production of D-arabitol was 125g/L and the conversion was 37.5%. The concentration of D-arabitol was growing. It provides a good perspective to D-arabitol industry.Meanwhile it established fermentation kinetic models including strain growth model, product formation model and medium consumption model. It obtained the model confidence interval is 88%. It indicated that this model could reflect well the actual fermentation process. It has certain guiding sense for simple batch fermentation.