Purification, characterization, optimization, and docking simulation of alkaline protease produced by Brevibacillus agri SAR25 using fish wastes as a substrate

Abstract

Recycling of protein-rich environmental wastes and obtaining more valuable products from these recycled products is a topic of interest for researchers. This study aims to produce, purify, and characterize the physicochemical and structural properties of the protease enzyme produced from Brevibacillus agri SAR25 using salmon fish waste as substrate and also to evaluate the effect of protease on the chicken feather, enzyme-ligand interactions, and active site surface area. The production of protease was optimum on 50 g/L fish waste, pH 8, 40 °C, 96 h, and 150 rpm. The alkaline protease was isolated using three-phase partitioning (TPP), a straightforward and efficient one-step method for purifying enzymes in industrial applications. TPP achieved a purification efficiency of 115 % with a 3.1-fold increase in concentration. As a result, the molecular weight of the purified protease was determined to be 50 kDa under optimal conditions of pH 9 and 45 °C. The 3D structure of the alkaline protease enzyme with the determined ligands was predicted by homology modeling using UCSF Chimera 1.17.3 software. Tween-20 ligand showed the best binding affinity by hydrogen bonding with amino acids 106 A, Asn 133 A, Gly 198, Asn 226, Glu 232 and hydrophobic interaction with His 135, Leu 283 in the active site of the alkaline protease enzyme, thus leading to the discovery of new semisynthetic enzymes of salmon fish waste. The activity and stability of Brevibacillus agri SAR25 alkaline protease over a wide range of temperatures and pH, and its relatively high stability in the presence of various metal ions, organic solvents, and surfactants indicate that it can be used as a biocatalyst for different industrial applications. This could lead to the creation of new enzymes made from recycled biological materials.