一株热带假丝酵母木糖醇高产新菌株的筛选

自木糖厂环境样品中分离出一株编号为1-18的产木糖醇分离物。在初始木糖浓度200g/L的条件下重复循环利用1-18细胞摇瓶发酵,木糖醇转化率高达0.91(木糖醇g/木糖g),接近理论极限值;木糖醇生成速率达6.7g/L·h。无论产物浓度,产物生成速率与产物转化率都达到了令人满意的高水平。1-18发酵液以40ml/kg·d的最大剂量饲喂小白鼠一周,受试动物未出现中毒反应。分离物1-18在木糖醇生产中显然具有重要的生物工程应用潜力。根据常规形态鉴别,生理生化实验测定,以及26S rDNA D1/D2区域核酸序列同源性比较分析,证实分离物1-18属于Candida tropicalis(热带假丝酵母)。分离物1-18已保存于中国典型培养物保藏中心,保藏编号CCTCC M 205067,其26S rDNA D1/D2区域核酸序列在GenBank的核酸序列登记号为DQ176428。

Good Strain Screened from Candida tropicalis to Produce Xylitol

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.