耐乙酸粘红酵母合成油脂

Lipid synthesis by an acidic acid tolerant Rhodotorula glutinis

摘要:

乙酸是木质纤维素在水解过程中的主要副产物，高浓度的乙酸严重影响产油微生物的生长和油脂合成。本文研究了粘红酵母对乙酸的耐受性及其利用乙酸合成微生物油脂的能力。结果表明，在初始葡萄糖、木糖浓度分别为6 g/L和44 g/L的混合糖培养基中，乙酸浓度低于10 g/L时，不会对菌体生长产生抑制作用，油脂合成还得到了促进。当乙酸添加量为10 g/L时，生物量、油脂产量、油脂含量较对照组分别提高了21.5%、171.2%和121.6%。进一步研究表明，粘红酵母具备利用乙酸合成油脂的能力，当以乙酸为唯一碳源，浓度为25 g/L时，油脂产量达到3.20 g/L，油脂质量得率为13%。微生物油脂成分分析表明，粘红酵母以乙酸为底物制得的油脂可以作为制备生物柴油的油脂原料，其主要成分为棕榈酸、硬脂酸、油酸、亚油酸和亚麻酸，其中饱和脂肪酸和不饱和脂肪酸含量分别为40.9%和59.1%。由于粘红酵母具有利用乙酸合成微生物油脂的能力，在以木质纤维素水解液为原料生产微生物油脂的脱毒过程中，一定浓度的乙酸可以不必脱除。

Abstract:

Acetic acid, as a main by-product generated in the pretreatment process of lignocellulose hydrolysis, significantly affects cell growth and lipid synthesis of oleaginous microorganisms. Therefore, we studied the tolerance of Rhodotorula glutinis to acetic acid and its lipid synthesis from substrate containing acetic acid. In the mixed sugar medium containing 6 g/L glucose and 44 g/L xylose, and supplemented with acetic acid, the cell growth was not inhibited when the acetic acid concentration was below 10 g/L. Compared with the control, the biomass, lipid concentration and lipid content of R. glutinis increased 21.5%, 171% and 122% respectively when acetic acid concentration was 10 g/L. Furthermore, R. glutinis could accumulate lipid with acetate as the sole carbon source. Lipid concentration and lipid yield reached 3.20 g/L and 13% respectively with the initial acetic acid concentration of 25 g/L. The lipid composition was analyzed by gas chromatograph. The main composition of lipid produced with acetic acid was palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid, including 40.9% saturated fatty acids and 59.1% unsaturated fatty acids. The lipid composition was similar to that of plant oil, indicating that lipid from oleaginous yeast R. glutinis had potential as the feedstock of biodiesel production. These results demonstrated that a certain concentration of acetic acid need not to be removed in the detoxification process when using lignocelluloses hydrolysate to produce microbial lipid by R. glutinis.