Fungal Biotransformation of Curcumin and Its Antibacterial Efficacy against Silkworm Flacherie Pathogens

Microbial transformation involves the production of new active biomolecules from natural products using microorganisms. This study focuses on exploring the microbial conversion of curcumin to develop improved antimicrobial agent for managing Flacherie disease in silkworms. The fungal cultures, Schizophyllum and Debaromyces species capable of converting curcumin into four metabolites. The chemical structures of the metabolites were analyzed using Nuclear Magnetic Resonance (NMR) spectroscopy, identifying them as tetrahydrocurcumin, hexahydrocurcumin, vanillin, and an unidentified metabolite. Antimicrobial activities of the metabolites were tested in vitro against various bacteria and showing the highest activity against Staphylococcus. A blend of the four metabolites was tested in systemic conditions on infected silkworms, resulting in a 14% increase in pupal survival against Staphylococcus. The new metabolites did not have any adverse effects on the economic characteristics of the silkworms. Overall, the converted compounds showed enhanced antimicrobial activity compared to the parent compounds, suggesting that curcumin derivatives could serve as a broad-spectrum antimicrobial agent.