This mini-review focused on the current advances in the development and the application of the antibacterial agents produced from probiotics strains against foodborne pathogens. Inhibitory activity of the pathogen growth could be achieved by co-culture with probiotics and/or the treatment of metabolites extracted from probiotics culture, whereas strain-dependent efficacy was mainly reported according to the bacterial species of the target pathogens. To overcome the limited antibacterial spectrum and the efficacy of the metabolites from probiotics, the recent research highlight the discovery of novel bioactive substances with broad range of the inhibitory activity of foodborne pathogens and mode-of-action which has not been reported as the major research goal. Moreover, understanding the distribution of functional and regulation genes coding the production of the antibacterial metabolites based on the bacterial genome analysis can provide the clues for the mechanisms of the pathogen control by using probiotics. Major strategies on the application of the genomics in this research area can be represented as follows: 1) functional annotation specialized for antimicrobial proteins, 2) assessment of the antibacterial effects followed by the general/functional annotation, 3) genome and metabolites analysis for the purification of antimicrobial proteins, 4) comparative genomics and the characterization of antimicrobial potential. Especially the relationship between phenotype-genotype based on genomic bioinformation with the results of the practical efficacy tests of bacterial metabolites as an active substance of disinfectants and/or preservatives can be expected to act as supportive research for broadening our knowledge regarding the key metabolic pathways associated with the production of antibacterials from probiotics.
Human intestinal flora is very diverse; with lactic acid bacteria (LAB) existing as part of the most vital gut microbes that improve host health. The application of LAB as a whole organism or its metabolite in the case of probiotic and bacteriocin respectively is extensive. Thus, the need to always bio-prospect for newer strains of LAB is essential. This study focused on isolating LAB from kunun-zaki and kindirmo, a fermented non-alcoholic beverage of non-dairy and dairy sources respectively, explored their physiological and biochemical properties, antibiotics sensitivity pattern and identified based on their 16S rRNA sequencing. A total of eighty isolates were selected sixty-six from kunun-zaki and fourteen from kindirmo in which 93.7% were bacilli and 6.3% were spherical in shape having 68.75% and 30% homofermentative and heterofermentative pathway respectively. All isolates have the ability to utilize glucose to produce lactic acid while their tolerance to pH 3 and salt concentration at 2%, 4% and 6.5% varied widely. Thirty-four isolates based on their physiological and biochemical properties were selected for molecular identification to ascertain their genera and species. Limosilactobacillus fermentum (68%); Lactiplantibacillus plantarum (6%) and Weissella confusa (3%) were confirmed species isolated. Thus, it was concluded that traditional fermented foods such as kunun-zaki and kindirmo are a good source to bio-prospect for LAB for product development, starter culture and probiotic study.
The detection of the genome-based antibiotic resistance gene is an essential analysis process for the purpose of verifying the safety of probiotic strains, including lactic acid bacteria. In this study, 4 analysis platforms (AMRFinderPlus, staramr, rgi, ABRicate) were used for cross-comparison of 782 genomes corresponding to 19 kinds of probiotic species notified as functional foods. As a result of the analysis, the relatively fewest number of antibiotic resistance genes were detected in strains belonging to the order Lactobacillales, and antibiotic resistance genes were detected in 322 genomes used in the case of 2 types of Enterococcus genus. In addition, the presence and type of antibiotic resistance gene detection showed a lot of difference even for the same genome sequence depending on the database and analysis algorithm used by the analysis platform. These results can be confused in evaluating the potential for transmission of antibiotic resistance genes inherent in specific lactic acid bacteria and predicting potential risks that may occur in the future. Accordingly, it is judged that the antibiotic resistance gene-related analysis criteria need to be established more clearly and specifically in the safety evaluation of probiotic bacteria.
Probiotic strain is known to regulate the immune system by colonizing in the intestine and interact with intestinal cell receptors of lymphoid tissue. In this study, safety of Streptococcus thermophilus KCTC14471BP and silk fibroin coating effects was evaluated with respect to mucin binding abilities and immune system modulation. S. thermophilus KCTC14471BP was coated with silk fibroin by adding 1% water-soluble calcium and 0.1% silk fibroin. S. thermophilus KCTC14471BP showed the high activities of leucine arylamidase and β-galactosidase. Regarding the antibiotic resistance tests, S. thermophilus KCTC14471BP was susceptible to ampicillin, vancomycin, gentamicin, kanamycin, streptomycin, erythromycin, clindamycin, tetracycline, and chloramphenicol. S. thermophilus KCTC14471BP coated with silk fibroin showed the improved mucin binding ability from 16.1% to 71.3% and was confirmed to have no cytotoxicity against RAW 264.7 macrophage. S. thermophilus KCTC14471BP coated with silk fibroin showed dose-dependently significant increases in pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. These results suggested that S. thermophilus KCTC14471BP can be expected as a promising probiotic bacteria for applications to food industries such as fermentation or functional foods.
This study aimed to optimize the fermentation condition of black bean using probiotic lactic acid bacteria (LAB) and to evaluate characteristics and antioxidant activity of LAB fermented and heat-treated black bean. Two LAB strains were selected by analysis of acid resistance, bile resistance, antimicrobial activity, and antioxidant activity, and identified as Lactiplantibacillus plantarum CH9 and Lactiplantibacillus plantarum SU18 by 16S rRNA sequencing. Both strains showed similar or higher acid resistance, bile resistance and antimicrobial activity, compared to Lacticaseibacillus rhamnosus GG, a commercial probiotic strain. The heat-killed cells of CH9 and SU18 strains showed significantly (p<0.05) higher DPPH and ABTS radical scavenging activities than live cells. Fermentation of black bean (30%) treated with Alcalase using the two selected strains was found to be optimal condition, increasing viable cell count of LAB up to 10.8 Log CFU/g. During the fermentation, the titratable acidity of Alcalase-treated black bean was notably increased with concomitant decrease in the pH. LAB fermentation significantly (p<0.05) increased antioxidant activity based on DPPH and ABTS radical scavenging activities as well as total phenol content. In addition, total phenol content and antioxidant activity were significantly (p<0.05) enhanced by heat processing (121C, 15 min) of the fermented products. These findings are expected to be useful for the development of various LAB-fermented foods containing heat-killed probiotics.