XYLITOL AND RIBOFLAVIN ACCUMULATION IN XYLOSE-GROWN CULTURES OF PICHIA-GUILLIERMONDII

Seven strains of Pichia guilliermondii (Candida guilliermondii, asexua l state) from diverse isolation sources were examined for the producti on of xylitol and riboflavin in xylose-grown cultures. Under the condi tions tested, all strains produced xylitol from xylose; conversion eff iciencies varied, on a strain-specific basis, from 7% to 36% of the in itial substrate. Four of seven strains metabolized xylitol immediately as xylose levels became depleted. The remaining three strains metabol ized xylitol slowly and incompletely. Surprisingly, utilization of xyl itol showed an apparent relationship with riboflavin production. Strai ns that readily metabolized xylitol produced at least threefold greate r levels of riboflavin than did strains that used xylitol slowly. More over, riboflavin accumulation took place during xylitol consumption. P . guilliermondii strains that produced the highest levels of riboflavi n on xylose produced significantly less riboflavin when grown on gluco se or directly on xylitol.