高产木糖醇酵母菌的筛选鉴定及两级法发酵特性  

Isolation and Identification of a High-yield Xylitol-producing Yeast Strain and Its Two-stage Fermentation Performances

作　　者：张金明[1] 耿安利 姚传义[1] 卢英华[1,3] 李清彪[1,3] 

机构地区：[1]厦门大学化学化工学院,福建厦门361005 [2]义安理工学院生命与化学技术学院,新加坡599489 [3]厦门大学化学生物学福建省重点实验室,福建厦门361005

出　　处：《厦门大学学报（自然科学版）》2011年第3期624-630,共7页Journal of Xiamen University：Natural Science

摘　　要：从300多种土壤样品中进行筛选,最终得到10株可耐受300 g/L木糖的酵母菌株,且其木糖醇转化率超过64.0%.其中酵母菌株SB18在150 g/L木糖下的木糖醇转化率为68.5%,为相同条件下转化率最大的菌株,并经18SrDNA测序鉴定为热带假丝酵母.酶活测定结果显示SB18木糖还原酶主要依赖辅因子还原型烟酰胺腺嘌呤二核苷酸磷酸(NADPH),其酶活性远大于木糖醇脱氢酶活性.对SB18进行两级法发酵条件研究,确定补充氮源为尿素和酵母提取物,接种量为0.5 g/L,转速转换时间为36 h.在此条件下由250 g/L木糖摇瓶发酵252 h得到207.65 g/L木糖醇,转化率为83.1%,达到理论值的91.8%.本研究表明酵母菌SB18在高浓度木糖醇的工业生产中具有很大的应用潜力.Xylose-utilizing yeasts isolated from soil samples in Singapore were screened for xylitol production in high xylose concentration.After several round of screening,10 strains were selected for their high tolerance to 300 g/L xylose concentration,which can convert xylose into xylitol with a yield greater than 64.0%.Strain SB18 exhibited the maximal xylitol yield of 68.5% from 150 g/L xylose,and then was identified as Candida tropicalis by 18S rDNA sequencing information.Enzyme assay results indicate that in strain SB18,xylose reductase（XR） is NADPH dependent and its activity is much higher than that of xylitol dehydrogenase（XDH）.A two-stage fermentation process was employed to investigate the cultivation condition of SB18.The results show that the best nitrogen sources are yeast extract and urea,innoculum size is 0.5 g/L,initial xylose concentration is 250 g/L,the optimal speed switch time is 36 h with a shaking speed of 250 r/min in the first stage,and a speed of 100 r/min afterwards.Under the optimal cultivation conditions,xylitol final concentration reached 207.65 g/L after 252 h incubation from 250 g/L,corresponding to a xylitol yield of 83.1% and 91.8% xylose-to-xylitol bioconversion efficiency.This work demonstrates that strain C.tropicalis SB18 has great potentials in industrial xylitol bioproduction in high xylose concentration.

关 键 词：木糖醇生产 两级法发酵 热带假丝酵母 木糖还原酶 木糖醇脱氢酶 

分 类 号：Q939.9[生物学—微生物学]