Physical and Chemical Fermentation Conditions Affect the Growth and Metabolite Production of Endophytic Fungi Athelia rolfsii

Background: The effort to explore antimicrobial agents isolated from an endophytic fungus of Coleus amboinicus resulted in the finding of a potential aromatic compound having methoxy, hydroxyl, and methyl groups produced by Athelia rolfsii. This compound exhibited antibacterial activities with IC50 values of <2 μg/mL against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Streptococcus mutans, and Pseudomonas aeruginosa. This study was aimed to determine the effect of varying fermentation conditions (types of media, carbon sources, nitrogen sources, temperature, and pH) on biomass, total metabolites, and bioactive compound production.

Materials and Methods: The fungal cultures were subjected to various treatment conditions and incubated for 12 days at 25°C 160 rpm followed by analyzing the biomass, metabolite, and bioactive compound production.

Results and Conclusion: The study found that although the maximum total metabolite production was achieved in the Tryptic Soy Broth medium, both biomass and bioactive compound production accumulated at the highest amount in Potato Dextrose Broth and Sabouraud Dextrose Broth media. Adding 1% of different types of carbon sources did not significantly enhance biomass, total metabolite, and bioactive compound production. Three types of organic nitrogen sources used in this study did not significantly affect biomass and total metabolite production, but adding peptone produced the highest amount of bioactive compound. Supplementing inorganic source of nitrogen to the culture medium decreased the production. While pH 5.5 was found to be the optimum condition for total metabolite production, pH 6–7 resulted in higher productivity of the bioactive compound. The total metabolite production was best produced at 25°C, whereas higher temperatures were needed to get optimum bioactive and biomass production. This study found that the total metabolite production was 7.8 times higher when the culture was grown in PDB medium supplemented with 1% sucrose and 1% peptone and incubated at 27°C at pH 6.5; whereas a 15% increase was observed in the bioactive compound production.