Effect of Protaetia brevitarsis seulensis larvae fermented by Bacillus subtilis PB2110 on nutritional composition and immunomodulatory activity

Abstract Protaetia brevitarsis seulensis (white-spotted flower chafer) larvae are rich in amino acids and fatty acids, making them an environmentally sustainable and promising alternative protein source. Fermentation is recognised as an effective approach to enhance nutrient availability and influence the nutritional profile of biological materials. This study aimed to investigate whether fermenting P. brevitarsis larvae with Bacillus subtilis PB2441 prior to extraction could improve their nutritional composition and immunomodulatory effects. The larvae were either extracted using papain alone (PE) or fermented with B. subtilis PB2441 after papain treatment (PEP). The fermented extract (PEP) exhibited significantly higher levels of amino acids and fatty acids, resulting in an improved nutritional profile. In addition, PEP showed stronger antioxidant activity, enhanced nitric oxide (NO) production, upregulated immune-related biomarker expression, and increased both splenocyte proliferation and natural killer (NK) cell cytotoxicity compared to the non-fermented extract. Neither extract exhibited cytotoxic effects. These results indicate that fermentation-assisted extraction can effectively enhance the nutritional value and immunological functionality of P. brevitarsis larvae. Furthermore, this study supports the use of fermentation as a means to improve the nutritional potential of edible insects, reinforcing their applicability as sustainable ingredients in the food and feed sectors.