Protein and amino acid solubilization using bacillus cereus, bacillus velesensis, and chryseobacterium sp. from chemical extraction protein residue

The exploitation of natural resources and increased environmental pollution have stressed the need for more valued use of residues generated by the fish processing plants, and species with low commercial value. Protein hydrolysis processes—whether chemical or enzymatic—generate insoluble proteins from bones, scales, and skin, which are not recovered and are often used as animal feed or disposed off into the environment. As an alternative, insoluble proteins could be converted in useful biomass protein concentrates or amino acids, by using microbial proteases. This work examines the solubilization of insoluble proteins discarded in the process of pH change in fish residues from Whitemouth croaker (Micropogonias furnieri), through the use of bacterial proteases. Temperature and pH conditions in the fermentations were adjusted for each microorganism and time was set at 96 h. Two substrates (acid and alkaline), three microorganism strains, and the substrate concentration used were examined. Among the three strains, Bacillus velesensis reached the higher proteolytic activity (47.56 U mL−1), followed by Chryseobacterium sp. with 23.46 U mL−1. Bacillus cereus (3.13 U mL−1) showed low proteolytic activity. B. velesensis was the bacterium that presented better results with the analyzed substrates, achieving larger amount of soluble protein and free amino acids. The findings showed that these bacteria could be used to solubilize proteins from fish byproducts, which may be particularly useful to increase the yield of hydrolysis process or food formulations