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Development of Biphasic Culture System for an Entomopathogenic Fungus Beauveria bassiana PfBb Strain and Its Virulence on a Defoliating Moth Phauda flammans (Walker)

Summary

Researchers developed an efficient two-stage fermentation process to mass-produce Beauveria bassiana PfBb, a fungus that kills defoliating moths damaging Ficus trees. The first stage grows the fungus in liquid to produce active spores, which are then transferred to solid substrates to produce hardy, long-lasting conidia. The optimized process produces high quantities of effective fungal spores that can be stored at refrigerator temperature for over a year while maintaining their pest-killing ability.

Background

Beauveria bassiana is an entomopathogenic fungus used as a biological control agent for insect pests. The PfBb strain has high host specificity to Phauda flammans, a serious defoliating pest of Ficus trees in China and India. Biphasic fermentation systems are efficient for industrial-scale production of entomopathogenic fungi biopesticides.

Objective

This study optimized the biphasic fermentation system of B. bassiana PfBb by screening medium compositions and fermentation conditions for both liquid and solid fermentations. The researchers aimed to develop cost-effective mass production methods and maintain conidia validity and virulence during storage.

Results

Optimal liquid fermentation conditions were: glucose (40 g/L) and yeast extract (15 g/L) as carbon and nitrogen sources with C:N ratio of 17:1, inoculation concentration of 1×10⁸ conidia/mL, 50 mL inoculum, 180 rpm rotation speed, pH 7, and 26°C. For solid fermentation, wheat bran and chaff at 8:2 ratio with 20% inoculum content, 50% water content, and 3 days dark fermentation yielded highest conidia production. Conidia stored at 4°C for one year maintained virulence against all larval instars of P. flammans.

Conclusion

The optimized biphasic culture system provides essential support for commercial production of B. bassiana PfBb-based biopesticides. Storage at 4°C maintains conidial validity and virulence for extended periods, enabling practical implementation of biological control programs. The high cadaver rates and maintained virulence across larval instars demonstrate the potential for large-scale pest management applications.
  • Published in:Journal of Fungi (Basel),
  • Study Type:Experimental Research,
  • Source: 10.3390/jof11030202, PMC11943346, 40137240
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