Category Archives: Bacteriocin

Research – Lactic Acid Bacteria and Bacteriocins: Novel Biotechnological Approach for Biopreservation of Meat and Meat Products

MDPI

Meat and meat products are perishable in nature, and easily susceptible to microbial contamination and chemical deterioration. This not only results in an increased risk to health of consumers, but also causes economic loss to the meat industry. Some microorganisms of the lactic acid bacteria (LAB) group and their ribosomal-synthesized antimicrobial peptides—especially bacteriocins—can be used as a natural preservative, and an alternative to chemical preservatives in meat industry. Purified or partially purified bacteriocins can be used as a food additive or incorporated in active packaging, while bacteriocin-producing cells could be added as starter or protective cultures for fermented meats. Large-scale applications of bacteriocins are limited, however, mainly due to the narrow antimicrobial spectrum and varying stability in different food matrixes. To overcome these limitations, bioengineering and biotechnological techniques are being employed to combine two or more classes of bacteriocins and develop novel bacteriocins with high efficacy. These approaches, in combination with hurdle concepts (active packaging), provide adequate safety by reducing the pathogenicity of spoilage microorganisms, improving sensory characteristics (e.g., desirable flavor, texture, aroma) and enhancing the shelf life of meat-based products. In this review, the biosynthesis of different classes of LAB bacteriocins, their mechanism of action and their role in the preservation of meats and meat products are reviewed.

Research – Bacteriocin Production by Escherichia coli during Biofilm Development

MDPI

Escherichia coli is a highly versatile bacterium ranging from commensal to intestinal pathogen, and is an important foodborne pathogen. E. coli species are able to prosper in multispecies biofilms and secrete bacteriocins that are only toxic to species/strains closely related to the producer strain. In this study, 20 distinct E. coli strains were characterized for several properties that confer competitive advantages against closer microorganisms by assessing the biofilm-forming capacity, the production of antimicrobial molecules, and the production of siderophores. Furthermore, primer sets for E. coli bacteriocins–colicins were designed and genes were amplified, allowing us to observe that colicins were widely distributed among the pathogenic E. coli strains. Their production in the planktonic phase or single-species biofilms was uncommon. Only two E. coli strains out of nine biofilm-forming were able to inhibit the growth of other E. coli strains. There is evidence of larger amounts of colicin being produced in the late stages of E. coli biofilm growth. The decrease in bacterial biomass after 12 h of incubation indicates active type I colicin production, whose release normally requires E. coli cell lysis. Almost all E. coli strains were siderophore-producing, which may be related to the resistance to colicin as these two molecules may use the same transporter system. Moreover, E. coli CECT 504 was able to coexist with Salmonella enterica in dual-species biofilms, but Shigella dysenteriae was selectively excluded, correlating with high expression levels of colicin (E, B, and M) genes observed by real-time PCR. View Full-Text

Research – Novel Bacteriocin a Promising New Treatment for Resistant Listeria monocytogenes

Contagion Live

A novel bacteriocin appears promising as a new treatment option for antibiotic-resistant Listeria monocytogenes infection just as a multistate outbreak of the foodborne bacteria has claimed 2 lives in the United States.

With a fatality rate that can reach as high as 30%, L monocytogenes is considered a pressing public health threat that can have a serious impact on immunocompromised individuals and pregnant women, newborn children, and the elderly.

Because of its high mortality rate and increasing resistance to currently available antibiotics, treating L monocytogenes is becoming more and more challenging. But investigators with RMIT University in Melbourne, Australia, have discovered a promising new treatment in the form of a bacteriocin produced by Lactobacillus plantarum B21. The research team presented their findings at the American Society for Microbiology (ASM) and the European Society for Clinical Microbiology and Infectious Diseases (ESCMID) Conference on Drug Development to Meet the Challenge of Antimicrobial Resistance.

Investigators played with multiple culture conditions to find a set that would foster high bacterial growth and/or high bacteriocin production. They also used gas chromatography mass spectrometry (GC‐MS)-based metabolomics to evaluate cellular and functional behavior of L plantarum B21. The structure of bacteriocin was analyzed using 2‐dimensional nuclear magnetic resonance spectroscopy (NMR). In order to assess the effectiveness of bacteriocin against a range of target strains of bacteria, the team relied on well diffusion assays and electron microscopy.