Report on aflatoxin-binding activity of galactan exopolysaccharide produced by Weissella confusa KR780676

Antifungal mechanisms investigation of lactic acid bacteria against Aspergillus flavus: through combining microbial metabolomics and co-culture system

AIMS

To develop antifungal lactic acid bacteria (LAB) and investigate their antifungal mechanisms against Aspergillus flavus in aflatoxin (AF) production.

METHODS AND RESULTS

We isolated 179 LABs from cereal-based fermentation starters and investigated their antifungal mechanism against A. flavus through liquid chromatography-mass spectrometry and co-culture analysis techniques. Of the 179 isolates, antifungal activity was identified in Pediococcus pentosaceus, Lactobacillus crustorum, and Weissella paramesenteroides. These LABs reduced AF concentration by (i) inhibiting mycelial growth, (ii) binding AF to the cell wall, and (iii) producing antifungal compounds. Species-specific activities were also observed, with P. pentosaceus inhibiting AF production and W. paramesenteroides showing AF B1 binding activity. In addition, crucial extracellular metabolites for selecting antifungal LAB were involved in the 2',3'-cAMP-adenosine and nucleoside pathways.

CONCLUSIONS

This study demonstrates that P. pentosaceus, L. crustorum, and W. paramesenteroides are key LAB strains with distinct antifungal mechanisms against A. flavus, suggesting their potential as biological agents to reduce AF in food materials.

The Weissella and Periweissella genera: up-to-date taxonomy, ecology, safety, biotechnological, and probiotic potential

Bacteria belonging to the genera Weissella and Periweissella are lactic acid bacteria, which emerged in the last decades for their probiotic and biotechnological potential. In 2015, an article reviewing the scientific literature till that date on the taxonomy, ecology, and biotechnological potential of the Weissella genus was published. Since then, the number of studies on this genus has increased enormously, several novel species have been discovered, the taxonomy of the genus underwent changes and new insights into the safety, and biotechnological and probiotic potential of weissellas and periweissellas could be gained. Here, we provide an updated overview (from 2015 until today) of the taxonomy, ecology, safety, biotechnological, and probiotic potential of these lactic acid bacteria.

Functional and health-promoting properties of probiotics' exopolysaccharides; isolation, characterization, and applications in the food industry

Exopolysaccharides (EPS) are extracellular sugar metabolites/polymers of some slim microorganisms and, a wide variety of probiotics have been broadly investigated for their ability to produce EPS. EPS originated from probiotics have potential applications in food, pharmaceutical, cosmetology, wastewater treatment, and textiles industries, nevertheless slight is recognized about their function. The present review purposes to comprehensively discuss the structure, classification, biosynthesis, extraction, purification, sources, health-promoting properties, techno-functional benefits, application in the food industry, safety, toxicology, analysis, and characterization methods of EPS originated from probiotic microorganisms. Various studies have shown that probiotic EPS used as stabilizers, emulsifiers, gelling agents, viscosifiers, and prebiotics can alter the nutritional, texture, and rheological characteristics of food and beverages and play a major role in improving the quality of these products. Numerous studies have also proven the beneficial health effects of probiotic EPS, including antioxidant, antimicrobial, anti-inflammatory, immunomodulatory, anticancer, antidiabetic, antibiofilm, antiulcer, and antitoxin activities. Although the use of probiotic EPS has health effects and improves the organoleptic and textural properties of food and pharmaceutical products and there is a high tendency for their use in related industries, the production yield of these products is low and requires basic studies to support their products in large scale.

Complete Genome Sequence of Weissella confusa LM1 and Comparative Genomic Analysis

The genus Weissella is attracting an increasing amount of attention because of its multiple functions and probiotic potential. In particular, the species Weissella confusa is known to have great potential in industrial applications and exhibits numerous biological functions. However, the knowledge on this bacterium in insects is not investigated. Here, we isolated and identified W. confusa as the dominant lactic acid bacteria in the gut of the migratory locust. We named this strain W. confusa LM1, which is the first genome of an insect-derived W. confusa strain with one complete chromosome and one complete plasmid. Among all W. confusa strains, W. confusa LM1 had the largest genome. Its genome was the closest to that of W. confusa 1001271B_151109_G12, a strain from human feces. Our results provided accurate evolutionary relationships of known Weissella species and W. confusa strains. Based on genomic analysis, the pan-genome of W. confusa is in an open state. Most strains of W. confusa had the unique genes, indicating that these strains can adapt to different ecological niches and organisms. However, the variation of strain-specific genes did represent significant correlations with their hosts and ecological niches. These strains were predicted to have low potential to produce secondary metabolites. Furthermore, no antibiotic resistance genes were identified. At the same time, virulence factors associated with toxin production and secretion system were not found, indicating that W. confusa strains were not sufficient to perform virulence. Our study facilitated the discovery of the functions of W. confusa LM1 in locust biology and their potential application to locust management.

Bacterial exopolysaccharides for improvement of technological, functional and rheological properties of yoghurt

Exopolysaccharides (EPS) are known to have technological and functional applications in food industry including dairy based products such as yoghurt. Yoghurt is a widely consumed dairy based product due to pleasant taste and texture, as well as a source of nutrients and bioactive compounds. At the same time, structural, rheological and sensorial properties are important in the production of good quality yoghurt. Various natural hydrocolloids including EPS with stabilizing and texture enhancing properties could be useful in enhancing these desirable properties. Apart from that, EPS may enhance various other functional properties of yoghurt such as antioxidant and prebiotic potential. Based on its prebiotic property, symbiotic products could be developed by combining EPS and probiotic bacterial strains. EPS has potential to provide physical and micro structural stability, thereby enhancing the protein distribution and viscoelastic properties. Main focus of the present review is to provide an insight on the action of EPS as a functional hydrocolloid on the technological, rheological and functional properties of yoghurt and related products.

Aflatoxin B1 and Sterigmatocystin Binding Potential of Non-Lactobacillus LAB Strains

Research on the ability of lactic acid bacteria (LAB) to bind aflatoxin B1 (AFB1) has mostly been focusing on lactobacilli and bifidobacteria. In this study, the AFB1 binding capacities of 20 Enterococcus strains belonging to E. casseliflavus, E. faecalis, E. faecium, E. hirae, E. lactis, and E. mundtii, 24 Pediococcus strains belonging to species P. acidilactici, P. lolii, P. pentosaceus, and P. stilesii, one strain of Lactococcus formosensis and L.garviae, and 3 strains of Weissella soli were investigated in MRS broth at 37 °C at 0.2 µg/mL mycotoxin concentration. According to our results, among non-lactobacilli LAB, the genera with the best AFB1 binding abilities were genus Pediococcus, with a maximum binding percentage of 7.6% by P. acidilactici OR83, followed by genus Lactococcus. For AFB1 bio-detoxification purposes, beside lactobacilli, pediococci can also be chosen, but it is important to select a strain with better binding properties than the average value of its genus. Five Pediococcus strains have been selected to compare their sterigmatocystin (ST) binding abilities to AFB1 binding, and a 2-3-fold difference was obtained similar to previous findings for lactobacilli. The best strain was P. acidilactici OR83 with 18% ST binding capacity. This is the first report on ST binding capabilities of non-Lactobacillus LAB strains.