Abstract:

In this study, tilapia processing byproducts were used as the major substrate for solid-state fermentation
to produce composite active peptides with antimicrobial and nutritional properties. In order to improve the yield of
antimicrobial lipopeptides, the medium and fermentation conditions were optimized. The lipopeptide components generated
were analyzed and quantitated by a high performance liquid chromatography-mass spectrometry method. The optimization
was performed by applying one-factor-at-a-time method and response surface methodology. The results showed that the
main antimicrobial lipopeptides produced were surfactin (m/z 995.20, 1 008.20 and 1 058.20, respectively) and iturin (m/z
1 044.30 and 1 071.20, respectively). Under the optimized conditions: tilapia processing byproducts to wheat bran
ratio of 3.48:1 (m/m), initial moisture content of 69.34%, fermentation time of 61.69 h, fermentation temperature of
28.97 ℃, amount of sugarcane bagasse of 6% and inoculum volume of 5 mL/100 g, the yield of antimicrobial lipopeptides
reached up to 7.32 g/kg (the actual yield was 7.29 g/kg), which increased 8.5 folds compared with that before optimization.
The product obtained was found to consist of a mixture of lipopeptides.

Key words: Bacillus natto NT-6, tilapia processing byproducts, solid-state fermentation, response surface methodology, antimicrobial lipopeptides, high performance liquid chromatography-mass spectrometry