Enhanced production of mycelial biomass and ganoderic acid in submerged culture of Ganoderma applanatum ACCC-52297 elicited by feeding rutin

Abstract

In this study, it was found that supplementation of 0.6 g/L rutin could improve the fermentation performance of Ganoderma applanatum ACCC-52297 in terms of mycelial growth and ganoderic acid (GA) production. Albeit retarded mycelial growth was detected at the first 36 h in the submerged culture of G. applanatum ACCC-52297 with the addition of rutin, kinetic model analysis revealed that rutin could improve mycelial growth and GA synthesis at the later phase of the fermentation (after 36 h). As such, rutin post-feeding strategy was proposed to elevate the final GA titer and at the same time minimize the inhibitory effect of rutin on mycelia growth. As a result, higher GA production (293 mg/L) and dry mycelia weight (DCW) (30.5 g/L) were achieved, GA were increased by 102.1 and 7.32%, and DCW were increased by 200 and 130% compared with those culture without addition of rutin and addition of 0.6 g/L rutin at the beginning of fermentation, respectively. Rheology analysis showed that addition of rutin was adversely related with the broth consistency coefficient and apparent viscosity, possibly due to the inhibitory effect of rutin on the biosynthesis of some macromolecules such as proteins and polysaccharides, which could partially account for the improved production of mycelia and GA during G. applanatum ACCC-52297 fermentation. Quericean, a metabolite of rutin, was also found to accumulate within the mycelium. It was concluded that rutin does not participate in the synthesis of GA as a precursor but rather facilitates the synthesis of GA and mycelia biomass by increasing the dissolved oxygen concentration during fermentation. Key words: Ganoderma applanatum, rutin, ganoderic acid, dry cell weight, rheolog.