Multiple bacteriocin production in lactic acid bacteria.

Bacteriocin production in lactic acid bacteria (LAB) has always been considered as a highly desirable trait as it enhances the strain's utility in different industrial applications. Bacteriocin producing LAB strains are considered to have higher bacterial fitness as they are able to easily establish themselves into target microbial niche and hence are more effective starter cultures in food fermentation and/or probiotic strains. The rapid advancement in genomic research revealed the true bacteriocin producing capacity of some select novel LAB strains capable of producing multiple bacteriocins which further improves their utility in different application systems.

Secondary Metabolites of Actinomycetales as Potent Quorum Sensing Inhibitors Targeting Gram-Positive Pathogens: In Vitro and In Silico Study.

Anti-virulence agents are non-bacteriostatic and non-bactericidal emerging therapeutic options which hamper the production of virulence factors in pathogenic flora. In and , regulation of virulence genes' expression occurs through the cyclic peptide-mediated accessory gene regulator () and its ortholog quorum sensing systems, respectively. In the present study, we screened a set of 54 actinomycetales secondary metabolites as novel anti-virulence compounds targeting quorum sensing system of the Gram-positive bacteria.

Molecular characterization of the possible regulation of multiple bacteriocin production through a three-component regulatory system in Enterococcus faecium NKR-5-3.

Enterococcus faecium NKR-5-3 produces multiple-bacteriocins, enterocins NKR-5-3A, B, C, D, and Z (Ent53A, Ent53B, Ent53C, Ent53D, and Ent53Z). However, the biosynthetic mechanisms on how their productions are regulated are yet to be fully understood. In silico analysis revealed putative promoters and terminators in the enterocin NKR-5-3ACDZ gene cluster, and the putative direct repeats (5'-ATTTTAGGATA-3') were conserved upstream of each promoter.

Transcriptome profile of carbon catabolite repression in an efficient l-(+)-lactic acid-producing bacterium Enterococcus mundtii QU25 grown in media with combinations of cellobiose, xylose, and glucose.

Enterococcus mundtii QU25, a non-dairy lactic acid bacterium of the phylum Firmicutes, is capable of simultaneously fermenting cellobiose and xylose, and is described as a promising strain for the industrial production of optically pure l-lactic acid (≥ 99.9%) via homo-fermentation of lignocellulosic hydrolysates. Generally, Firmicutes bacteria show preferential consumption of sugar (usually glucose), termed carbon catabolite repression (CCR), while hampering the catabolism of other sugars.

Kunkecin A, a New Nisin Variant Bacteriocin Produced by the Fructophilic Lactic Acid Bacterium, FF30-6 Isolated From Honey Bees.

FF30-6 isolated from healthy honey bees synthesizes the bacteriocin, which exhibits antimicrobial activity against . The bacteriocin, kunkecin A, was purified through three-step chromatography, and mass spectrometry revealed that its relative molecular mass was 4218.3.

Processing and secretion of non-cognate bacteriocins by EnkT, an ABC transporter from a multiple-bacteriocin producer, Enterococcus faecium NKR-5-3.

EnkT is an ATP-binding cassette (ABC) transporter produced by Enterococcus faecium NKR-5-3, which is responsible for the secretion of multiple bacteriocins; enterocins NKR-5-3A, C, D, and Z (Ent53A, C, D, and Z). EnkT has been shown to possess a tolerant recognition mechanism that enables it to secrete the mature Ent53C from a chimeric precursor peptide containing the leader peptide moieties that are derived from different heterologous bacteriocins. In this study, to further characterize EnkT, we aimed to investigate the capacity of EnkT to recognize, process, and secrete non-cognate bacteriocins, which belong to different subclasses of class II.

Correction to: Dynamic simulation of continuous mixed sugar fermentation with increasing cell retention time for lactic acid production using QU 25.

[This corrects the article DOI: 10.1186/s13068-020-01752-6.].

Dynamic simulation of continuous mixed sugar fermentation with increasing cell retention time for lactic acid production using QU 25.

Background: The simultaneous and effective conversion of both pentose and hexose in fermentation is a critical and challenging task toward the lignocellulosic economy. This study aims to investigate the feasibility of an innovative co-fermentation process featuring with a cell recycling unit (CF/CR) for mixed sugar utilization. A l-lactic acid-producing strain QU 25 was applied in the continuous fermentation process, and the mixed sugars were utilized at different productivities after the flowing conditions were changed.

Lowering effect of viable QU 19 on the rise in postprandial glucose.

In the present study, we investigated the glucose-decreasing action of lactic acid bacteria (LAB). The finding of this study could be helpful for people in controlling their blood sugar levels. The LAB candidate was isolated from a Japanese fermented food and identified as by an analysis of its genome sequence.

Non-carbon loss long-term continuous lactic acid production from mixed sugars using thermophilic Enterococcus faecium QU 50.

In this study, a non-sterile (open) continuous fermentation (OCF) process with no-carbon loss was developed to improve lactic acid (LA) productivity and operational stability from the co-utilization of lignocellulose-derived sugars by thermophilic Enterococcus faecium QU 50. The effects of different sugar mixtures on LA production were firstly investigated in conventional OCF at 50°C, pH 6.5 and a dilution rate of 0.

Mosaic Cooperativity in Slow Polypeptide Topological Isomerization Revealed by Residue-Specific NMR Thermodynamic Analysis.

Slow polypeptide conformational changes on time scales of >1 s are generally assumed to be highly cooperative two-state transitions, reflecting the high energy barrier. However, few experimental characterizations have tested the validity of this assumption. We performed residue-specific NMR thermodynamic analysis of the 27-residue lantibiotic peptide, nukacin ISK-1, to characterize the isomerization between two topological states on the second time scale.

Smart fermentation engineering for butanol production: designed biomass and consolidated bioprocessing systems.

There is a renewed interest in acetone-butanol-ethanol (ABE) fermentation from renewable substrates for the sustainable and environment-friendly production of biofuel and platform chemicals. However, the ABE fermentation is associated with several challenges due to the presence of heterogeneous components in the renewable substrates and the intrinsic characteristics of ABE fermentation process. Hence, there is a need to select optimal substrates and modify their characteristics suitable for the ABE fermentation process or microbial strain.

Relation between cell-bound exopolysaccharide production via plasmid-encoded genes and rugose colony morphology in the probiotic Lactobacillus brevis KB290.

The probiotic Lactobacillus brevis KB290 is a natural producer of cell-bound exopolysaccharide (EPS), and the plasmid-encoded glycosyltransferase genes are responsible for this EPS production. KB290 forms unique rugose colonies inside an agar medium; this characteristic is useful for detecting and enumerating KB290 in the gut or feces. However, the genetic elements associated with this morphology remain unclear.

The association between gut microbiota development and maturation of intestinal bile acid metabolism in the first 3 y of healthy Japanese infants.

The gut microbial community greatly changes in early life, influencing infant health and subsequent host physiology, notably through its collective metabolism, including host-microbiota interplay of bile acid (BA) metabolism. However, little is known regarding how the development of the intestinal microbial community is associated with maturation of intestinal BA metabolism. To address this, we monitored the succession of gut bacterial community and its association with fecal BA profile in the first 3 y of ten healthy Japanese infants.

Constitutive expression of phosphoketolase, a key enzyme for metabolic shift from homo- to heterolactic fermentation in QU 25.

Phosphoketolase (PK) is responsible for heterolactic fermentation; however, the PK gene of QU 25, , is transcribed constitutively, even under homolactic fermentation conditions. In order to deduce the regulatory mechanisms of PK activity in QU 25, XfpA levels in QU 25 cells under hetero- and homolactic fermentation conditions were tested using western blotting. The results showed that the XfpA protein expression was similar under both conditions and that the expression products formed complexes, most likely homodimers, indicating that the regulation of PK activity is downstream of translation.

Plasmid-encoded glycosyltransferase operon is responsible for exopolysaccharide production, cell aggregation, and bile resistance in a probiotic strain, Lactobacillus brevis KB290.

We demonstrate here that exopolysaccharide (EPS) production, cell aggregation, and bile resistance in Lactobacillus brevis KB290 are conferred by three eps genes (gtf27, gtf28, and orf29) located on the 42.4-kb plasmid pKB290-1. The predicted products of gtf27 and gtf28 belong to the membrane-bound glycosyltransferase family whereas the orf29 gene product showed homology with the ABC transporter.

Complete Genome Sequence of Enterococcus faecium QU50, a Thermophilic Lactic Acid Bacterium Capable of Metabolizing Xylose.

Herein, we report the complete genome sequence of QU50, isolated from Egyptian soil and exhibiting intermediate susceptibility to vancomycin. The genome contains a 2,535,796-bp circular chromosome and two plasmids of 196,595 bp and 17,267 bp. IS-like sequences were not found.

Semi-hydrolysate of paper pulp without pretreatment enables a consolidated fermentation system with in situ product recovery for the production of butanol.

Utilization of lignocellulosic biomasses for biobutanol fermentation usually requires costly processes of pretreatment and enzymatic hydrolysis. In this study, paper pulp (93.2% glucan) was used as a starting biomass material to produce biobutanol.

The lantibiotic nukacin ISK-1 exists in an equilibrium between active and inactive lipid-II binding states.

The lantibiotic nukacin ISK-1 exerts antimicrobial activity through binding to lipid II. Here, we perform NMR analyses of the structure of nukacin ISK-1 and the interaction with lipid II. Unexpectedly, nukacin ISK-1 exists in two structural states in aqueous solution, with an interconversion rate on a time scale of seconds.

Recognizability of heterologous co-chaperones with Streptococcus intermedius DnaK and Escherichia coli DnaK.

Streptococcus intermedius DnaK complements the temperature-sensitive phenotype of an Escherichia coli dnaK null mutant only when co-chaperones DnaJ and GrpE are co-expressed. Therefore, whether S. intermedius DnaK and E.

Circular and Leaderless Bacteriocins: Biosynthesis, Mode of Action, Applications, and Prospects.

Bacteriocins are a huge family of ribosomally synthesized peptides known to exhibit a range of bioactivities, most predominantly antibacterial activities. Bacteriocins from lactic acid bacteria are of particular interest due to the latter's association to food fermentation and the general notion of them to be safe. Among the family of bacteriocins, the groups known as circular bacteriocins and leaderless bacteriocins are gaining more attention due to their enormous potential for industrial application.

Novel biobutanol fermentation at a large extractant volume ratio using immobilized Clostridium saccharoperbutylacetonicum N1-4.

Product inhibition by butanol and acetone is a known drawback in acetone-butanol-ethanol (ABE) fermentation. Extractive fermentation improves butanol production by several ABE-producing Clostridium spp., but only low volume ratios (<4) of extractant to broth (V/V) have been studied.

Urban Diets Linked to Gut Microbiome and Metabolome Alterations in Children: A Comparative Cross-Sectional Study in Thailand.

Loss of traditional diets by food globalization may have adverse impact on the health of human being through the alteration of gut microbial ecosystem. To address this notion, we compared the gut microbiota of urban ( = 17) and rural ( = 28) school-aged children in Thailand in association with their dietary habits. Dietary records indicated that children living in urban Bangkok tended to consume modern high-fat diets, whereas children in rural Buriram tended to consume traditional vegetable-based diets.