Screening of microorganisms for xylitol production and fermentation behavior in high concentrations of xylose

Microorganisms with the ability to produce xylitol from high concentrations of xylose were screened from soils by enrichment culture using xylose as a sole carbon source. The selected strain was classified and determined as Candida sp. according to a taxonomic identification. In this strain, various conditions for xylitol production were investigated. Organic nutrients such as peptone and yeast extract were essential for xylitol production, and the optimal initial pH and kLa were between 4.0 and 6.0, and 5.2/h, respectively. Under the optimal condition, xylitol production from 200 g/l of xylose was 173 g/l after 5 days incubation, a 99.3% yield of the theoretical value. In order to produce a higher concentration of xylitol, a fed-batch culture of xylose was carried out by feeding 2.0 g of xylose per 10 ml of culture medium. The production from 4.0 g of xylose was 2.9 g of xylitol (concentration of 256 g/l) after 11.5 days which is a yield of 85.0%.