Stimulated production of triterpenoids of Inonotus obliquus using methyl jasmonate and fatty acids

• Triterpenoid production by I. obliquus under submerged fermentation.
• Trametenolic acid, 3β-hydroxy-lanosta-8,24-dien-21-al, inotodiol, and betulin.
• Addition of MeJA with Tween-80 or fatty acids stimulates the production.
• Fatty acids are less effective than MeJA on the production.
• Different effect on biosynthesis of individual tritepenoid components.

Found in Europe, Asia, and North America, Inonotus obliquus is a rare yet popular medicinal mushroom. One type of the most biologically active components found in I. obliquus is triterpenoids. The aim of this study is to investigate the feasibility of enhancing triterpenoid production in shake flask cultures of I. obliquus by adding methyl jasmonate (MeJA) as an exogenous elicitor and fatty acids as stimulatory agents. The appropriate addition concentration and adding time of MeJA were determined to be 50 μM and on Day 6. The production of total triterpenoids (99.72 mg/g DW and 1.01 g/L) increased by 65.8% and 65.6%, respectively, compared with the control. Of the fatty acids tested, linoleic acid was proved to be the most effective in enhancing total triterpenoid production. With an addition of 1.5 g/L on Day 6, the production of total triterpenoids rose from 64.93 mg/g DW in the control to 94.61 mg/g DW. HPLC analysis showed that the production of four highly bioactive triterpenoids, i.e., inotodiol, trametenolic acid, 3β-hydroxy-lanosta-8,24-dien-21-al, and betulin, was substantially increased by the supplementation of MeJA and fatty acids. The mycelia cultured with additional MeJA yielded 2.5 mg/g inotodiol, 2.2 mg/g trametenolic acid, 1.5 mg/g 3β-hydroxy-lanosta-8,24-dien-21-al, and 14.9 mg/g betulin, showing 3.0-, 5.5-, 4.7-, and 21.8-fold increments, respectively. Of the three fatty acids, linoleic acid was the most effective in enhancing the production of 3β-hydroxy-lanosta-8,24-dien-21-al and betulin (3.5- and 20.4-fold increments, respectively), while oleic acid was the most effective in enhancing the production of inotodiol and trametenolic acid (2.5- and 4.1-fold increments, respectively). This study demonstrated that the addition of MeJA and fatty acids effectively enhanced the production of bioactive metabolites in submerged cultures of I. obliquus. The mechanisms were preliminarily discussed.