Structural and genetic insights into a poly-γ-glutamic acid with in vitro antioxidant activity of Bacillus velezensis VCN56.

Poly-γ­glutamic acid (γ­PGA) produced by Bacillus species is a natural biopolymer, which is widely used in various fields including food, pharmaceuticals, and cosmetics. In this study, the screening of 19 Bacillus isolates derived from traditionally fermented foods revealed that Bacillus velezensis VCN56 was the most potent γ­PGA producer. The maximum concentration of crude γ­PGA was 32.9 ± 1.5 g/L in the PGA-3 medium containing glycerol, citric acid, sodium glutamate, NH4Cl, and starch. The resulting γ-PGA was purified and then characterized by HPLC, FTIR, and 1H-NMR analyses. Molecular weight of purified γ­PGA was estimated to be 98 kDa with a polydisperse index of 2.04. Notably, the pure γ­PGA showed significant in vitro antioxidant scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (72.0 ± 1.5%), hydroxyl (81.0 ± 0.6%), and superoxide (43.9 ± 0.8%) radicals at the concentration of 4 mg/mL. Using whole-genome sequencing, the genetic organization of pgs operon responsible for γ­PGA biosynthesis in B. velezensis VCN56 differs from those in other Bacillus genomes. Further genome analysis revealed metabolic pathways for γ-PGA production and degradation. For the first time, the present study provides a better understanding of γ-PGA with a promising antioxidant activity produced by B. velezensis at the phenotypic, biochemical, and genomic levels, which hold potential applications in the foods, cosmetics, and pharmaceutical industries.

Whole genome sequence analysis of Bacillus amyloliquefaciens strain S2.5 as a potential probiotic for feed supplement in livestock production.

BACKGROUND: Supplementing probiotics in livestock feed is increasing due to concerns over the potential harm caused by antibiotics and other chemical growth promoters. Several Bacillus sp. have been used as probiotic supplements for livestock. In this study, Bacillus amyloliquefaciens S2.5 was isolated from freshwater and its potential probiotic characteristics were evaluated in vitro. The whole genome of strain S2.5 was sequenced, and its probiotic traits were annotated using bioinformatic tools. RESULTS: Both vegetative cells and spores of strain S2.5 remained stable throughout the 1.5 h of gastric juice and 48 h of intestine simulation. The strain S2.5 harbored the ability to produce glucoamylase, carboxymethyl cellulase, protease, and chitinase. It is also susceptible to all six tested antibiotics. The complete genome sequence shows genes related to acid-bile tolerance, environmental stress resistance, hydrolases, and adhesion to gut mucosa, confirming probiotic traits in the in vitro experiments. CONCLUSIONS: B. amyloliquefaciens S2.5 demonstrated potential probiotic characteristics and its genetic profile in the in vitro experiments. Further in vivo assessments of B. amyloliquefaciens S2.5 on livestock and poultry should be performed to assess its practical application.

Identification of differentially expressed genes and metabolism signaling pathway in the spleen of broilers supplemented with probiotic Bacillus spp.

Probiotics are essential in the body's nutrients, improving the ratio of meat to meat, immune response, and preventing diseases. In this study, RNA-sequencing (RNA-seq) was used to identify the differentially expressed genes (DEGs), enriched related pathways, and Gene Ontology (GO) terms among blank negative control (NC), supplemented with Bacillus spp. (BS) and commercial probiotic (PC) groups after a 42-day fed supplementation. The results showed that 2005, 1356, and 2189 DEGs were significantly altered in BS vs. NC, PC vs NC, and BS vs PC groups, respectively. On the other hand, 9 DEGs were further validated by qRT-PCR, indicating that the qRT-PCR and RNA-Seq results were more consistent. Therefore, the GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DEGs showed that the DEGs were mainly enriched to metabolism signalling pathways (alpha-linolenic acid metabolism, linoleic acid metabolism, tryptophan metabolism, tyrosine metabolism, ether lipid metabolism, and metabolic pathway, etc) and immune response pathways (cytokine-cytokine receptor interaction, MAPK signalling pathway, and intestinal immune network for IgA production, neuroactive ligand-receptor interaction etc). These results will provide a better understanding of the role of probiotics in chicken development and provide basic information on the genetic development of chickens.

Screening of lactic acid bacteria for their potential use as aromatic starters in fermented vegetables.

Lactic acid fermentation is a traditional process to preserve foods and to modify their organoleptic properties. This process is generally conducted in a spontaneous way, allowing indigenous lactic acid bacteria (LAB) of the matrix and of the environment to compete and grow. The aim of this study was to better characterise LAB strains ability to modify aroma profiles in fruit and vegetable matrices, by focusing on two key enzymatic activities: ß-glucosidase and alcohol dehydrogenase (ADH). Firstly, 200 LAB isolated from Cambodian and Vietnamese fermented foods were screened for their ß-glucosidase activity and duplicate isolates identified through RAPD-PCR analysis were discarded. Thereby, 40 strains were found positive for ß-glucosidase using p-nitrophenyl-ß-D-glucopyranoside as substrate. Among them, 14 displayed an activity greater than 10 nmol/min/mg dry cell. Thirteen were identified as Lactiplantibacillus (L.) plantarum and one as L. pentosus. Secondly, four strains of different phenotypes for ß-glucosidase activity were tested for ADH activity. The highest reduction ability for hexanal and (E)-2-hexenal was obtained for Limosilactobacillus (L.) fermentum V013-1A for which no ß-glucosidase activity was detectable. The three other strains (L. plantarum C022-2B, C022-3B, and V0023-4B2) exhibited a lower reduction ability and only for hexanal. Thirdly, mashed tomatoes were fermented with these four strains individually to evaluate their ability to release volatile compounds from the tomato precursors. Fifty-eight volatile compounds were identified and quantified by HS-SPME/GC-MS. Untreated tomatoes were rich in aldehydes. The tomatoes fermented with L. plantarum strains were rich in ketones whereas those with L. fermentum were rich in alcohols. However, for the generation of terpenoids that provide flower and fruit flavours, our screening of ß-glucosidase activity was not able to explain the differences among the strains. For ADH activity, L. fermentum exhibited a high activity in fermentation as most of the target aldehydes and ketones disappeared and were replaced by their corresponding alcohols. The L. plantarum strains exhibited a lower activity but with an important substrate-selectivity diversity. A better knowledge of the functionality of each LAB strain in the food matrix will permit to predict and shape the aroma profiles of fermented food.

Prospects for Food Fermentation in South-East Asia, Topics From the Tropical Fermentation and Biotechnology Network at the End of the AsiFood Erasmus+Project.

Fermentation has been used for centuries to produce food in South-East Asia and some foods of this region are famous in the whole world. However, in the twenty first century, issues like food safety and quality must be addressed in a world changing from local business to globalization. In Western countries, the answer to these questions has been made through hygienisation, generalization of the use of starters, specialization of agriculture and use of long-distance transportation. This may have resulted in a loss in the taste and typicity of the products, in an extensive use of antibiotics and other chemicals and eventually, in a loss in the confidence of consumers to the products. The challenges awaiting fermentation in South-East Asia are thus to improve safety and quality in a sustainable system producing tasty and typical fermented products and valorising by-products. At the end of the "AsiFood Erasmus+ project" (www.asifood.org), the goal of this paper is to present and discuss these challenges as addressed by the Tropical Fermentation Network, a group of researchers from universities, research centers and companies in Asia and Europe. This paper presents current actions and prospects on hygienic, environmental, sensorial and nutritional qualities of traditional fermented food including screening of functional bacteria and starters, food safety strategies, research for new antimicrobial compounds, development of more sustainable fermentations and valorisation of by-products. A specificity of this network is also the multidisciplinary approach dealing with microbiology, food, chemical, sensorial, and genetic analyses, biotechnology, food supply chain, consumers and ethnology.