Investigating the antibacterial effects of some Lactobacillus, Bifidobacterium and acetobacter strains killed by different methods on Streptococcus mutans and Escherichia coli

Bacterial Strains Isolated from Stingless Bee Workers Inhibit the Growth of Apis mellifera Pathogens

Apis mellifera bees are an important resource for the local economy of various regions in Argentina and the maintenance of natural ecosystems. In recent years, different alternatives have been investigated to avoid the reduction or loss of colonies caused by pathogens and parasites such as Ascosphaera apis, Aspergillus flavus, and Paenibacillus larvae. We focused on bacterial strains isolated from the intestine of native stingless bees, to elucidate their antagonistic effect on diseases of A. mellifera colonies. For this purpose, worker bees of the species Tetragonisca fiebrigi, Plebeia spp., and Scaptotrigona jujuyensis were captured from the entrance to tree hives and transported to the laboratory, where their intestines were extracted. Twenty bacterial colonies were isolated from the intestines, and those capable of inhibiting enterobacteria in vitro and producing organic acids, proteases, and chitinases were selected. Four genera, Levilactobacillus, Acetobacter, Lactiplantibacillus, and Pantoea, were selected and identified by the molecular marker that codes for the 16S rRNA gene. For inhibition assays, cell suspensions and cell-free suspensions were performed. All treatments showed significant antibacterial effects, in comparison with the controls, against P. larvae and antifungal effects against A. apis and A. flavus. However, the mechanisms by which these bacteria inhibit the growth of these pathogens were not studied.

Synergistic effects of lactobacillus strains and Acetobacter pasteurianus on jujube puree's product functionality and quality

Commercial lactic acid bacteria strains and indigenous Chinese acetic acid bacterium were co-cultivated bi- and tri-culturally in Junzao jujube puree for the first time to investigate their effects on physicochemical properties and quality attributes. Lactic-acetic acid bacteria co-fermentation was performed at 37 °C for 48 h during the anaerobic fermentation phase and at 30 °C for 144 h during aerobic fermentation. FTIR results showed that predominant wave numbers at 1716-1724 cm-1 and 2922-3307 cm-1 exhibited discernible alterations in the lactic-acetic acid co-fermented jujube purees compared to the control sample. Pearson correlation analysis showed that the flavonoid and flavonol contents were responsible for the enhanced 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl scavenging activities of the fermented jujube purees. Consequently, fermented jujube puree from tricultures of Lactobacillus casei, Lactobacillus plantarum, and Acetobacter pasteurianus gave the best results, with the highest phenolics, flavonoid, and flavonol contents and the most improved antioxidative properties and color. Overall, lactic-acetic acid bacteria co-culture holds significant promise in valorizing Junzao jujube purees for functional ingredient development, paving the way for further research into similar interactions with different food matrices or microbial strains.

Postbiotics: Current Trends in Food and Pharmaceutical Industry

Postbiotics are non-viable bacterial products or metabolic byproducts produced by probiotic microorganisms that have biologic activity in the host. Postbiotics are functional bioactive compounds, generated in a matrix during anaerobic fermentation of organic nutrients like prebiotics, for the generation of energy in the form of adenosine triphosphate. The byproducts of this metabolic sequence are called postbiotics, these are low molecular weight soluble compounds either secreted by live microflora or released after microbial cell lysis. A few examples of widely studied postbiotics are short-chain fatty acids, microbial cell fragments, extracellular polysaccharides, cell lysates, teichoic acid, vitamins, etc. Presently, prebiotics and probiotics are the products on the market; however, postbiotics are also gaining a great deal of attention. The numerous health advantages of postbiotic components may soon lead to an increase in consumer demand for postbiotic supplements. The most recent research aspects of postbiotics in the food and pharmaceutical industries are included in this review. The review encompasses a brief introduction, classification, production technologies, characterization, biological activities, and potential applications of postbiotics.