The mechanistic study of adding polyunsaturated fatty acid to promote triterpenoids production in submerged fermentation of Sanghuangporus baumii

Background: Triterpenoids are the major bioactive constituents of the edible and medicinal mushroom San-ghuangporus baumii. The polyunsaturated fatty acid is an excellent stimulator that promotes the production of triterpenoids significantly. In this study, the detailed underlying mechanisms between linolenic acid and tri-terpenoids production were further investigated. Results: GC-MS analysis, the release of cell constituents, SEM observation and MDA content determination showed the changes in cell membrane composition, permeability and morphology. A higher unsaturated/satu-rated fatty acid ratio, better membrane permeability and fluidity, and enhanced degree of mycelial wrinkles and lipid peroxidation were observed. Furthermore, the expression levels and enzyme activities of HMGS, HMGR, FPPS, SQS and SE were significantly upregulated by adding linolenic acid at specific period. Conclusion: All mechanism explorations indicated that the effects of exogenous linolenic acid on triterpenoids production were tightly correlated with substrate supply, change of cell membrane and metabolic regulation of triterpenoids biosynthetic pathway.