Soybeans agroindustrial residues as Staphylococcus epidermidis and S. aureus biofilm inhibitors

Abstract

The reuse of agroindustrial waste has been the subject of several studies since they present rich chemical composition and their disposal generates costs to industries and harmful potential to the environment. Compounds present in soybean residues may have a potential antibiofilm activity, a property still very little explored in this raw material. The seek for active compounds against biofilms, has been extremely important, since they represent a challenge in clinical and industrial environments. Thus, this study aimed to evaluate the potential antibiofilm and antimicrobial activities of extracts obtained from soybeans processing residues against Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. Antibacterial and antibiofilm activities of two crude extracts were evaluated using absorbance (620 nm), colony-forming units (CFU) counting, and the crystal violet method, respectively. The safety of these compounds was assessed using the alternative model Caenorhabditis elegans. The extract obtained from fragments of the grain and stalks (E1) had its chemical characterization investigated and was submitted fractionation by ultrafiltration. The proteomic and metabolomic analysis of an active fraction was performed using liquid chromatography and mass spectrometry. E1 (4 mg/mL) inhibited 75 % of the S. epidermidis biofilm formation with no inhibition of bacterial growth. Antibiofilm activity of E1 was lost when it was submitted to a heat treatment, while the enzymatic treatment with proteinase K led to a loss of 30 % in the activity of the extract, suggesting that the antibiofilm molecules may be of protein origin. When submitted to the ultrafiltration process, the antibiofilm activity was observed mainly when two fractions (fraction> 50 kDa (R50) and fraction <10 kDa (F10′)) were combined, suggesting that the biological activity is dependent on the combination of the active molecules. The metabolomic analysis of F10′ indicated the presence of flavonoids, lipids, peptides, organic compounds and nucleosides while in the proteomic analysis of R50 a total of 19 proteins were identified. The extract E1 and the active fraction (R50+F10′) showed low toxicity in C. elegans. This work shows that soybeans agroindustrial residues may be a potential source of molecules with activity against bacterial biofilms.