Enhanced production of ganoderic acids in static liquid culture of Ganoderma lucidum under nitrogen-limiting conditions

The effect of nitrogen limitation on the production of the antitumor compounds, ganoderic acids (GAs), by Ganoderma lucidum and on transcription levels of triterpene biosynthesis genes in this mushroom was investigated. At 3 mM glutamine, a maximal content of GA-Mk, GA-T, GA-S, and GA-Me was 2.16, 11.76, 31.09, and 7.04 μg/mg cell dry weight, respectively, which was 2.8-, 5.8-, 8.3-, and 5.1-fold that obtained at 60 mM glutamine. The transcription levels of biosynthetic genes encoding 3-hydroxy-3-methylglutaryl-CoA reductase, farnesyl pyrophosphate synthase, squalene synthase, lanosterol synthase, and a putative nitrogen regulator, AreA, were up-regulated by 37-, 18-, 4.5-, 3.2-, and 13-fold, respectively, in nitrogen limitation conditions, suggesting that increased GAs biosynthesis may result from higher expression of those genes. This study demonstrated a useful strategy for enhancing GAs production and provided useful information for further investigation on its biosynthesis regulation.