New and potent production platform of the acetylcholinesterase inhibitor huperzine A by gamma-irradiated Alternaria brassicae under solid-state fermentation

Abstract

Huperzine-A (HupA) is an emerging, powerful, and promising natural acetylcholinesterase inhibitor. Despite that, the achieved yields of HupA from microbial sources are still far from the industrial applications. Accordingly, this paper was conducted to valorize solid-state fermentation (SSF) as an efficient production platform of HupA. Four agro-industrial wastes, namely rice bran, potato peel, sugarcane bagasse, and wheat bran, were tested and screened as cultural substrates for the production of HupA by the endophytic Alternaria brassica under SSF. Maximum HupA production was attained on using rice bran moistened by Czapex's dox mineral broth. In the effort to increase the HupA titer, supplementation of the best moistening agent by different carbon and nitrogen sources was successfully investigated. Additionally, factors affecting HupA production under SSF including substrate concentration, moistening level, and inoculum concentration were optimized using response surface methodology. A Box-Behnken design was applied for generating a predictive model of the interactions between these factors. Under the optimum conditions of 15 g rice bran, inoculum concentration of 5 × 10⁶ spores mL^-1, and 60% moisture level, HupA concentration was intensified to 518.93 μg g^-1. Besides, HupA production by the fungal strain was further enhanced using gamma-irradiation mutagenesis. The final HupA production was significantly intensified following exposure to 0.5 KGy gamma radiation to 1327 μg g^-1, which represents a 12.85-fold increase. This is the first report on the successful production of the natural fungal metabolite HupA under SSF. Moreover, the achieved yield in this study using agro-industrial wastes may contribute to reducing the cost of HupA manufacture.Key points• Different agro-industrial by-products were tried as cultural substrates for the production of the acetylcholinesterase inhibitor HupA under SSF for the first time.• Factors affecting HupA production under SSF were optimized using response surface methodology.• The final HupA production was intensified following exposure to gamma radiation recording 1327 μg g^-1, which represents a 12.85-fold increase.

Keywords: Agro-industrial wastes; Alternaria brassicae; Gamma radiation; Huperzine A; Solid-state fermentation; Sustainable production.