Genome shuffling of Lactobacillus plantarum 163 enhanced antibacterial activity and usefulness in preserving orange juice

Enhanced antimicrobial activity of lactic acid bacteria through genome shuffling and genetic variability among shuffled strains

In this investigation, lactic acid bacteria (LAB) isolated from milk were tested for their antibacterial properties and improved the antimicrobial activity of these isolates using genome shuffling. A total of sixty-one isolates were found in eleven samples, which were then tested using the agar diffusion method for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa. Thirty-one strains exhibited antibacterial activity against at least one of the tested pathogens, with an inhibitory zone's diameter varying between 15.0 and 24.0 mm. Two isolates that showed the highest antimicrobial activity were identified as Lactobacillus plantarum CIP 103151 and Lactobacillus plantarum JCM 1149 according to 16S rRNA analysis. In the present study, applying genome shuffling approach significantly enhanced the antibacterial activity of L. plantarum. The initial populations were obtained via ultraviolet irradiation and were treated using the protoplast fusion method. The ideal condition for the production of protoplasts was 15 mg/ml of lysozyme and 10 μg/ml of mutanolysin. After two rounds of fusion, ten recombinants exhibited a significant increase in the inhibition zones versus S. aureus, S. typhimurium, P. aeruginosa, and E. coli, reaching up to 1.34, 1.31, 1.37, and 1.37-fold increase in inhibitory zone respectively. Random Amplified Polymorphic DNA results showed clear differences in DNA banding patterns among the wild strain of L. plantarum CIP 103151 and the three selected shuffled strains using primers 1283 & OPA09. On the other hand, no change was obtained using primers OPD03 neither among the wild strain and the three recombinant strains nor among the three shuffled strains.

Characterization, High-Density Fermentation, and the Production of a Directed Vat Set Starter of Lactobacilli Used in the Food Industry: A Review

Lactobacilli have been widely concerned for decades. Bacteria of the genus Lactobacillus have been commonly employed in fermented food to improve the appearance, smell, and taste of food or prolong its shelf-life. They comprise 261 species (by March 2020) that are highly diverse at the phenotypic, ecological, and genotypic levels. Some Lactobacilli strains have been documented to be essential probiotics, which are defined as a group of living microorganisms that are beneficial to the health of the host when ingested in sufficiency. However, the characterization, high-density fermentation, and the production of a directed vat set (DVS) starter of Lactobacilli strains used in the food industry have not been systematically reported. This paper mainly focuses on reviewing Lactobacilli as functional starter cultures in the food industry, including different molecular techniques for identification at the species and strain levels, methods for evaluating Lactobacilli properties, enhancing their performance and improving the cell density of Lactobacilli, and the production techniques of DVS starter of Lactobacilli strains. Moreover, this review further discussed the existing problems and future development prospects of Lactobacilli in the food industry. The viability and stability of Lactobacilli in the food industry and gastrointestinal environment are critical challenges at the industrial scale. The new production equipment and technology of DVS starter of Lactobacilli strains will have the potential for large-scale application, for example, developing low-temperature spray drying, freezing granulation drying, and spray freeze-drying.