Screening of endophytic fungi for producing functional oils rich in diacylglycerol and analysis of the oil composition

The production of functional oils by fermentation using microbial has been paid much attention due to its advantages such as small footprint, short production cycle, and high oil yield. In the present study, the endophytic fungi strains were isolated and screened from natural Taxus chinensis var. mairei, and their biological identification was carried out. Then, the oil content, oil yield, and oil composition of the endophytic fungi were analyzed. The results showed that a total of 18 endophytic fungal strains were obtained. Among them, two strains belonged to the genus Fusarium, two strains belonged to the genus Lasidiplodia, two strains belonged to the genus Trichoderma, three strains belonged to the genus Colletotrichum, and three strains belonged to the genus Diporthe. The other six strains belonged to the genus Phomopsis, Cladosporium, Pestalotiopsis, Botryosphaeria, Penicillium, and Talaromyces, respectively. Under the same culture conditions, the strain Fusarium lateritium (coded as 2.S33Y) had the highest oil content, reaching 27.60% of cell dry weight. The oil productivity of Lasiodiplodia pseudotheobromae (coded as 2.S31) had a maximum value of 1.91 g/L. Endophytic fungal oils mainly contained triacylglycerol, diacylglycerol, and free fatty acids. The highest triacylglycerol content was found in the oils from the Diaporthe sp. (coded as S511), reaching 92.25%. The strain Fusarium lateritium (coded as 2.S33Y) had the highest yield of diacylglycerol, reaching 335.22 mg/L; Oils from the Cladosporium sp. (coded as S431) had the highest content of diacylglycerol, reaching 19.20%. But S431 had a low productivity of diacylglycerol (102.91 mg/L). The strain 2.S33Y was the most suitable for biosynthesis of functional lipid diacylglycerol. The oil fraction extracted from 2.S33Y was mainly composed of palmitic acid (29.79%), steric acid (29.36%), oleic acid (11.07%), and linoleic acid (27.14%).