Impact of submerged culture conditions on growth and bioactive metabolite produced by endophyte Hypocrea spp. NSF-08 isolated from Dillenia indica Linn. in North-East India

Abstract

Summary An endophytic fungus, associated with tropical tree species Dillenia indica Linn., has a broad-spectrum antimicrobial property against human and plant pathogenic microorganisms. The fungus was identified as Hypocrea spp. NSF-08, a teleomorphic genus of Trichoderma, based on morphological, sporulation and molecular characteristics. The effect of various culture conditions, supplementary carbon, nitrogen sources and amino acid amendment on growth and antimicrobial agent production by the fungus was determined. The basal medium, enriched with glycerol (2%) as carbon source and ammonium nitrate as nitrogen source, promoted the biosynthesis of secondary metabolite. Optimum temperature required for maximum production of antimicrobial agent was 25 °C and pH 5.5, respectively, in an incubation period of eight days, while specific rate of product formation was at maximum on the 4th day. Amendment of amino acid alanine with glucose and glutamic acid in combination with glycerol, sucrose and fructose enhanced the production of bioactive metabolite by the fungus. The antimicrobial agent produced by Hypocrea spp. was extracted with ethyl acetate as solvent and purified by TLC. The purified active compound with UV λ-max 242 nm got the lowest minimum inhibitory concentration (MIC) against Staphylococcus aureus and Fusarium oxysporum, whereas no activity recorded against Pseudomonas aeruginosa.