Sustainable valorization of fish byproducts and acid whey through lactic acid bacteria fermentation into bioactive hydrolysates

Abstract

The growing accumulation of food byproducts and waste imposes environmental and economic challenges, highlighting the need for sustainable valorization strategies. This study investigated the usage of fish byproducts and acid whey through lactic acid bacteria (LAB) fermentation to produce bioactive fish protein hydrolysates (FPHs) with potential antioxidant and antibacterial properties. The effects of three formulations: acid whey (FAw), a starter culture (FLr), and their combination (FAwLr) on the fermentation and its products were systematically evaluated. LAB fermentation triggered protein hydrolysis, as demonstrated by the increased degrees of hydrolysis (DH). The fermentation process was also marked by significant microbial growth using FAwLr, with LAB populations above 10⁸ CFU mL⁻¹ by Day 3, accompanied by a rapid pH decline (<4.5). Viscosity of the fermented samples decreased in all formulations, showing smaller consistency indexes and larger flow behavior indexes, indicating enhanced protein hydrolysis and a reduced structural complexity of the system over time. Antioxidant activity, measured by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid), and FRAP (Ferric Reducing Antioxidant Power) assays, was significantly improved in all formulations containing acid whey. The antibacterial activity against Listeria innocua and Escherichia coli showed formulation-dependent effects. The combination of acid whey and LAB (FAwLr) exhibited the strongest antibacterial properties, lowering both the minimum inhibitory and bactericidal concentrations. These results highlight the synergistic effects of acid whey and LAB in producing multifunctional bioactive hydrolysates with both antioxidant and antibacterial activities, showcasing a sustainable approach to converting waste streams into value-added ingredients.