Metagenomic laccase-catalyzed crosslinking of wheat proteins for enhanced soybean meal nutritional value: applications in poultry feed and food industry

Soybean meal (SBM) is a major protein source for human and animal nutrition, particularly in broiler diets, due to its high amino acid content and digestibility. However, its use is limited by low solubility, poor emulsification, and weak foaming properties. Improving these characteristics is crucial for enhancing feed functionality and nutritional value. Laccase-mediated protein crosslinking using phenolic mediators offers an eco-friendly enzymatic strategy to modify protein structure and functionality. This study aimed to enhance the functional and nutritional quality of SBM by enzymatically crosslinking wheat albumin (WAP) and globulin (WGP) using a metagenomic laccase (PersiLac2) with phenolic mediators caffeic acid (CA) and vanillic acid (VA). Crosslinking increased the water-holding capacity (WHC) of SBM from 4.34 to 5.25 g/g and the oil-holding capacity (OHC) from 0.74 to 1.12 g/g, while solubility improved from 33.6% to 47.6%. The antioxidant activity of the crosslinked proteins also rose markedly, with ABTS and DPPH scavenging reaching 91% and 54%, respectively. SDS-PAGE confirmed higher molecular weight aggregates, indicating successful crosslinking. In WAP, foaming capacity increased from 30% to 120% and stability from 33% to 58%, while in WGP, VA raised foaming capacity to 44% and PersiLac2 improved stability to 33%. FTIR and SEM analyses showed enhanced secondary structure stability and smoother surface morphology in treated SBM. Metagenomic laccase-catalyzed crosslinking in the presence of natural phenolic mediators effectively improves SBM’s structural, antioxidant, and interfacial properties, providing a sustainable biocatalytic route for upgrading food and feed protein quality.