Growth and effective inhibition of pathogens of Cordyceps militaris cultured on Sakon Nakhon local rice

This study investigated the growth and antimicrobial activity of Cordyceps militaris cultivated on two media types—Formula 1 (glucose-based) and Formula 2 (sucrose-based)—using five local rice varieties from Sakon Nakhon Province: Hom Nang Nual, Red Jasmine, Red Sticky, Kham Noi, and Kham Bai Kiew rice. The growth experiment, spanning 70 days, was divided into three stages, during which the fresh and dry weights of fruiting bodies and bases were recorded. Results showed that Formula 2 with Red Jasmine rice supported the highest growth, yielding 9.65 ± 1.23 g (fresh) and 1.54 ± 0.05 g (dry) per bottle. In Formula 1, the highest yield was observed using Kham Noi rice, with 9.62 ± 1.01 g (fresh) and 0.71 ± 0.16 g (dry) per bottle. For antimicrobial testing, dried C. militaris samples were soaked in 95% ethanol for 48 h, filtered, and concentrated via rotary evaporation at 50 °C. The crude extracts were tested against Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli using the disc diffusion method at concentrations of 20,000 – 100,000 ppm. At 100,000 ppm, all extracts exhibited antibacterial activity. Notably, the extract from Red Jasmine rice in Formula 1 showed the highest inhibition against E. coli, with a clear zone of 12.50 ± 5.91 mm. Statistical analysis confirmed significant differences (p ≤ 0.01) in inhibitory effectiveness. These findings indicate that a sucrose-based medium enhances the yield and quality of C. militaris, and nutrient-rich local rice substrates contribute to its antimicrobial potential. The study supports the application of local rice in C. militaris cultivation and suggests potential for developing natural antimicrobial products for future medical use. GRAPHICAL ABSTRACT HIGHLIGHTS Sucrose-based medium with Red Jasmine rice yielded the highest growth of Cordyceps militaris in both fresh and dry weights. The crude extract from C. militaris cultivated on Red Jasmine rice demonstrated the strongest inhibition against E. coli, showing the largest inhibition zone. Local rice varieties from Sakon Nakhon demonstrated strong potential as substrates for cultivating C. militaris for natural antimicrobial product development.