Kefir is a fermented dairy product with well recognized probiotic properties. Recently, consumer interest in fermented products with probiotic microorganisms has increased due to the accumulating evidence of the effects of kefir microorganisms on the modulation of gut microbiota and their antimicrobial activity. Although the health properties of kefir have been reviewed in other works, the present review addresses the antimicrobial effects of kefir microbiota and associated compounds. The antimicrobial activity of kefir microorganisms could derive from different mechanisms. The microorganisms' capacity to adhere to the intestinal epithelium, preventing the adhesion of pathogens, and their immunomodulation properties are among the mechanisms suggested. Bacteria and yeast isolated from kefir have been shown to have in vivo and in vitro antimicrobial activity against enteropathogenic bacteria and spoilage fungi. However, most reports have focused their approach on single-strain antimicrobial properties; evaluation of antimicrobial activity of cocultures of kefir microbiota and their potential mechanisms of action has been neglected. Kefir microbiota and associated compounds have shown promising antimicrobial effects; however, more research needs to be done to discern the mechanisms of action.

Marketing of raspberries is limited by their short postharvest life under refrigerated storage (<14 days). Short-term controlled atmospheres have been found to be effective in increasing the storage life of different crops and providing a more sustainable alternative to maintain postharvest quality compared to a continuous controlled atmosphere (CA). In this work, the effect of short-term CA treatments: early (15% CO 2 , 10% O 2 for 3 days + air for 11 days) and intermediate (3 days in air +3 days 15% CO 2 , 10% O 2 + 8 days in air) versus continuous CA on the postharvest quality of red raspberry cv. "Adelita" was evaluated. Short-term CA treatments significantly reduced weight loss during the first 6 days of storage. Early CA fruit showed longer sensory shelf life (SSL) values, and improved color parameters during storage compared to control.Efecto de atmósferas controladas en tiempos cortos sobre la calidad poscosecha y vida de anaquel sensorial de frambuesa roja (Rubus idaeus L.) RESUMENLa comercialización de frambuesa roja se ve limitada por la corta vida poscosecha de este fruto en almacenamiento refrigerado (<14 días). El uso de atmósferas controladas (AC) aplicadas en tiempos cortos ha resultado efectivo en incrementar la vida poscosecha de diferentes cultivos, siendo además una estrategia más sustentable para mantener la calidad de los productos comparado con el uso tradicional de AC aplicadas de manera continua durante el almacenamiento. En el presente estudio se evaluó el efecto de las AC aplicadas en tiempo-cortos: aplicación temprana (15% CO 2 , 10% O 2 por 3 días + aire por 11 días) e intermedia (3 días en aire + 3 días 15% CO 2 , 10% O 2 + 8 días en aire) contra. AC continua, en la calidad poscosecha de frutos de frambuesa roja cv. "Adelita". Tiempos cortos de AC redujeron significativamente la pérdida de peso durante los primeros 6 días de almacenamiento. La aplicación temprana de AC presentó mayores valores en la vida de anaquel sensorial y mejoró los parámetros de color durante el almacenamiento, comparados con el tratamiento control.

IntroductionDue to the increasing consumer demand for the development and improvement of functional foods containing probiotics, new probiotic candidates need to be explored as well as novel means to enhance their beneficial effects. Lactobacillus kefiranofaciens OSU-BDGOA1 is a strain isolated from kefir grains that has demonstrated probiotic traits. This species is the main inhabitant of kefir grains and is responsible for the production of an exopolysaccharide (EPS) whit vast technological applications and potential bioactivities. Research has shown that interkingdom interactions of yeast and lactic acid bacteria can enhance metabolic activities and promote resistance to environmental stressors.MethodsComparative genomic analyses were performed to distinguish OSU-BDGOA1 from other strains of the same species, and the genome was mined to provide molecular evidence for relevant probiotic properties. We further assessed the cumulative effect on the probiotic properties of OSU-BDGOA1 and Kluyveromyces marxianus bdgo-ym6 yeast co-culture compared to monocultures.ResultsSurvival during simulated digestion assessed by the INFOGEST digestion model showed higher survival of OSU-BDGOA1 and bdgo-ym6 in co-culture. The adhesion to intestinal cells assessed with the Caco-2 intestinal cell model revealed enhanced adhesion of OSU-BDGOA1 in co-culture. The observed increase in survival during digestion could be associated with the increased production of EPS during the late exponential and early stationary phases of co-culture that, by enhancing co-aggregation between the yeast and the bacterium, protects the microorganisms from severe gastrointestinal conditions as observed by SEM images. Immune modulation and barrier function for recovery and prevention of flagellin-mediated inflammation by Salmonella Typhimurium heat-killed cells (HKSC) in Caco-2 cells were also measured. OSU-BDGOA1 in mono- and co-culture regulated inflammation through downregulation of pro-inflammatory cytokine expression and increased membrane barrier integrity assessed by TEER, FD4 permeability, and expression of tight junctions.DiscussionThe results of the study warrant further research into the application of co-cultures of yeast and LAB in functional probiotic products and the potential to increase EPS production by co-culture strategies.

The microbiota composition of kefir grain and milk kefir was assessed via a metagenomic approach. Significant microorganisms were isolated and identified using molecular methods. A safety assessment was conducted based on antibiotic susceptibility and blood hemolysis. Probiotic traits such as resistance to gastric tract conditions, surface characteristics, adhesion to intestinal cells, and antibacterial activity were also assessed. Metagenomic analysis revealed that kefir grains are a more stable community with clear dominant species as compared to milk kefir. Lactobacillus kefiranofaciens BDGO‐A1, Lactobacillus helveticus BDGO‐AK2, and Lactobacillu kefiri strains showed tolerance to acidic pH and the presence of bile salts, adhesion capability to Caco‐2 cells, in vitro antibacterial activity, and the production of antibacterial proteins. In the metagenomic analysis, contigs associated with these species showed the presence of genes involved in exporting polyketide antibiotics and bacteriocin production. To fully exploit the potential probiotic properties of these microorganisms to help human health, further investigation is necessary to elucidate the mechanisms behind the biological activity and the genotypic characteristics of the isolated strains.

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