Abstract: The yeast isolate with a laboratory code of 1-18 cell was isolated from the environmental samples of a xylose manufacturing factory. The volumetric productivity of 6.7 g/L·h and xylitol yield of 0.91 g/g were reached respectively at initial xlylose concentration of 200 g/L by 1-18 isolate cell recycle fermentation. It reached a theoretical yield of xylitol from D-xylose. It is a satisfactory high xylitol production rate and xylitol yield. The test of acute toxicity on mice showed that the fermentation broth of isolated 1-18 cell does not show any toxic reaction at the maximum dosage of 40 ml/kg·d for one week. These results showed that the considerable biotechnological potential usage of 1-18 isolate exists for xylitol manufacture. On the bases of conventional morphological identification and assimilation physiological tests, its molecular characteristics was assayed by PCR amplification and sequencing of D1/D2 domain of 26S rDNA, so as to compare the nucleotide sequence of D1/D2 domain against GenBank+EMBL+DDBJ+PDB other known sequences from a BLAST search. All of the results led to the identification of 1-18 isolate as a new strain of Candida troplicalis. 1-18 isolate was submitted to China Center for Type Culture Collection and provided an accession number of CCTCCM 205067. Its nucleotide sequence of D1/D2 domain of 26S rDNA was registered in the GenBank nucleotide sequence databases under accession number DQ176428.

Key words: Candida tropicalis, xylitol, fermentation