ARTICLE Alternative Proteins Magazine October 2024 35 bacteria like Bacillus subtilis (2). Besides that, the defensin family, comprises six mature peptides, each with a molecular weight of around 4 kDa. These defensins are potent against E. coli, Staphylococcus aureus, and Salmonella species, as noted by Jingjing Zhang et al (2021)3. The antimicrobial effects of AMPs operate through diverse mechanisms, with the most well-studied being membrane disruption. These peptides interact with bacterial cell membranes, causing structural destabilization and increased permeability, which leads to cell lysis and death. Also, the interaction and binding with intracellular targets as well as immune modulation has been reported as antibacterial mode of actions of AMPs. Due to this broad spectrum potential antibacterial effect, it is challenging for bacteria to develop resistance to AMPs, unlike traditional antibiotics that target specific bacterial processes. AMPs offer several advantages, including their rapid action against bacteria and a low risk of inducing bacterial resistance, as it is difficult for bacteria to alter their membranes to resist AMP-induced disruption. Furthermore, AMPs have a short half-life, reducing their environmental persistence. These properties make AMPs promising candidates for use in animal feed applications to support pathogenic bacteria control, enhance animal health, and improve productivity in the livestock and aquaculture industries. With a mission to develop functional insect-based ingredients for animal feed and health, Entobel started with an in-house research project to investigate the AMPs properties found in its BSFL products. By exploring alternatives to antibiotics, Entobel aims to promote healthier fish and shrimp farming practices. One key area of research involves assessing the antimicrobial activity of extracts from fresh BSFL against bacterial infections in aquaculture, including Vibrio parahaemolyticus, a pathogen responsible for Acute Hepatopancreatic Necrosis Disease (AHPND) in shrimp and Streptococcus agalactiae, known to cause infections in freshwater fish. In a recent study, Entobel carried out preliminary research to assess the antimicrobial activity of whole, fresh BSFL which were reared on a diet of brewer's spent grain, with no additional treatments applied. The crude AMPs were extracted, followed by purification and fractionation based on molecular mass. To confirm the antimicrobial activity of each fraction, the Agar Inhibition Zone method was used. Additionally, SDS-PAGE, a technique for separating proteins based on their molecular mass, was used to determine the size of the peptides in each fraction. Two key fractions from the study demonstrated promising results. Fraction F3, which contained peptides ranging from 4 kDa to 7 kDa, showed antimicrobial activity against S. agalactiae, with a zone of inhibition measuring 13.5 mm at a 10.8 mg/mL concentration. Meanwhile, Fraction F4, accounting for the highest content in the crude extract and containing peptides smaller than 14 kDa, displayed antimicrobial activity against V. parahaemolyticus, and S. agalactiae. This fraction produced a zone of inhibition measuring 10.3 mm at a concentration of 21.5 mg/mL. (Figure 1 & 2) These initial findings suggest that the BSFL-derived AMPs possess an antimicrobial potential, particularly against some pathogenic bacteria in aquaculture. Figure 1. Diffusion inhibition zone of F3 and F4 against S. agalactiae
RkJQdWJsaXNoZXIy MTUxNjkxNQ==