Valorization of Malaysian fish sausage (Keropok Lekor) by-products into bioactive fish protein hydrolysate by Bacillus licheniformis fermentation: Influence of by-products characteristics on nutritional, antioxidant and antibacterial capacities

Abstract

Abstract The Malaysian fish sausage industry, Keropok Lekor (KL), generates large amounts of by-products (FBs), that are underutilised and inappropriately disposed of, resulting in negative environmental implications. This study aimed to transform the FBs into bioactive fish protein hydrolysate (FPH) via the Bacillus licheniformis fermentative approach. Besides the various FBs and strain type used, this study was significant for its detailed analysis exploring the effect of the FB's nutritional and amino acid contents on antioxidant and antibacterial activities, as well as the nutritional qualities of the FPHs. The B. licheniformis fermentation improved the FBs nutritional quality by increasing protein digestibility and essential amino acid content. The highest degree of hydrolysis (DH) was linked to soluble protein concentration, and there was a significant correlation (R2 = 0.9) between the DH and protein yields in the samples. The FPHs demonstrated stronger DPPH (32.5–58.4%) and ABTS (74.8–90.1%) antiradical activities, and ferrous chelating activity (25.3–59.9%) than that of the FBs (p < 0.05). The highest peptide concentration was found in fraction 3–10 kDa, which also showed the strongest inhibition of DPPH and ABTS, and ferrous chelating activity. The amino acid composition of the FPH significantly influenced the level of antioxidant activity. However, all FPHs showed no significant (p > 0.05) difference in growth inhibition against all tested pathogens compared to their FBs. Hence, KL FBs valorisation into high-value product like bioactive FPH by microbial fermentation serves as a green strategy to improve waste management and to advocate a circular and sustainable bioeconomy.