Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
Appl Microbiol Biotechnol. 2020 Apr;104(7):3133-3144. doi: 10.1007/s00253-020-10443-z. Epub 2020 Feb 19.
Six local isolates of yeasts were screened for cell mass and lipid production in mixed glucose and xylose medium. Candida tropicalis SY005 and Trichosporon (Apiotrichum) loubieri SY006 showed significant lipid accumulation of 24.6% and 32% (dry cell weight), respectively when grown in medium containing equal mass of both the sugars. SY005 produced relatively higher cell mass of 9.66 gL due to higher rate of sugar consumption, which raised the lipid productivity of the organism to 0.792 gLday as compared to 0.446 gLday in SY006. When grown with each sugar separately, the xylose consumption rate of SY005 was found to be 0.55 gL h after 4 days as compared to 0.52 gL h for SY006. Transcript expression of the high affinity xylose transporter (Cthaxt), xylose reductase (Ctxyl1), and xylitol dehydrogenase (Ctxyl2) of SY005 was monitored to unravel such high rate of sugar consumption. Expression of all the three genes was observed to vary in mixed sugars with Cthaxt exhibiting the highest expression in presence of only xylose. Expression levels of both Ctxyl1 and Ctxyl2, involved in xylose catabolism, were maximum during 24-48 h of growth, indicating that xylose utilization started in the presence of glucose, which was depleted in the medium after 96 h. Together, the present study documents that C. tropicalis SY005 consumes xylose concomitant to glucose during early period of growth, and it is a promising yeast strain for viable production of storage lipid or other high-value oleochemicals utilizing lignocellulose hydrolysate.
六种本地酵母菌株在混合葡萄糖和木糖的培养基中进行了细胞质量和脂质生产的筛选。当在含有等量两种糖的培养基中生长时，热带假丝酵母 SY005 和毛孢子菌（Apiotrichum）loubieri SY006 分别显示出 24.6%和 32%（干细胞重量）的显著脂质积累。由于较高的糖消耗率，SY005 产生相对较高的细胞质量 9.66 gL，这将生物体的脂质生产力提高到 0.792 gLday，而 SY006 为 0.446 gLday。当分别用每种糖生长时，SY005 的木糖消耗率在 4 天后发现为 0.55 gL h，而 SY006 为 0.52 gL h。监测 SY005 的高亲和力木糖转运蛋白（Cthaxt）、木糖还原酶（Ctxyl1）和木糖醇脱氢酶（Ctxyl2）的转录表达，以揭示这种高糖消耗率。在混合糖中观察到所有这三个基因的表达各不相同，Cthaxt 的表达在仅存在木糖时最高。参与木糖分解代谢的 Ctxyl1 和 Ctxyl2 的表达水平在生长的 24-48 小时内达到最高，表明木糖利用在葡萄糖存在的情况下开始，在 96 小时后培养基中的葡萄糖耗尽。总之，本研究表明，热带假丝酵母 SY005 在生长的早期阶段与葡萄糖同时消耗木糖，并且是利用木质纤维素水解物生产储存脂质或其他高价值油脂化学品的有前途的酵母菌株。
