Xylitol production in repeated fed batch cultivation

The ability of Candida parapsilosis to produce xylitol was tested using successive substrate supplies, and the importance of the amount of viable cells in enhancing the conversion rate was demonstrated. The suitability of this yeast for the production of xylitol was investigated in repeated fed-batch cultivation, using pure xylose or mixtures of xylose and glucose. The use of this process increased productivity by about 40% compared with simple batch cultivation without loss of yield of product on substrate. The presence of glucose in the culture medium seemed to stimulate the specific growth rate, but had no influence over other fermentative parameters.     

Yeast killer activity: A quantitative study

Summary A method, based on the reaction of a sensitive strain being transferred to medium prefermented by a killer strain, is proposed for the quantitative determination of the killer activity in fermentation media by Saccharomyces cerevisiae K1. This technique enables killer activity to be closely followed throughout the duration of batch fermentation. The killer activity in the culture medium is represented by the percentage decrease in viable biomass in comparison with the viable biomass of a reference culture.