Draft Genome Sequence of Enterococcus mundtii SCPM-O-B-8398 (E28), Isolated from Fermented Milk in the Moscow Region, Russian Federation

We report the draft genome sequence of the bacteriocin-producing Enterococcus mundtii strain SCPM-O-B-8398 (E28), which was isolated from fermented milk in the Moscow region, Russian Federation.

Improvement of Enantiomeric l-Lactic Acid Production from Mixed Hexose-Pentose Sugars by Coculture of Enterococcus mundtii WX1 and Lactobacillus rhamnosus SCJ9

Among 39 pentose-utilizing lactic acid bacteria (LAB) selected from acid-forming bacteria from the midgut of Eri silkworm, the isolate WX1 was selected with the highest capability to produce optically pure l-lactic acid (l-LA) from glucose, xylose and arabinose with furfural-tolerant properties. The isolate WX1 was identified as Enterococcus mundtii based on 16S rDNA sequence analysis. The conversion yields of l-LA from glucose and xylose by E. mundtii WX1 were 0.97 and 0.68 g/g substrate, respectively. Furthermore, l-LA production by E. mundtii WX1 in various glucose-xylose mixtures indicated glucose repression effect on xylose consumption. The coculture of E. mundtii WX1 and Lactobacillus rhamnosus SCJ9, a homofermentative LAB capable of producing l-LA from glucose clearly showed an improvement of l-LA production from 30 g/L total glucose-xylose (6:4). The results from Plackett–Burman design (PBD) indicated that Tween 80, MnSO4 and yeast extract (YE) were three medium components that significantly influenced (p < 0.05) l-LA production using the coculture strategy in the presence of 2 g/L furfural. Optimal concentrations of these variables revealed by central composite design (CCD) and response surface methodology (RSM) were 20.61 g/L YE, 1.44 g/L Tween 80 and 1.27 g/L MnSO4. Based on the optimized medium with 30 g/L total glucose-xylose (6:4), the maximum experimental l-LA value of 23.59 g/L reflecting 0.76 g/g substrate were achieved from 48 h fermentation at 37 °C. l-LA produced by coculture cultivated under standard MRS medium and new optimized conditions were 1.28 and 1.53 times higher than that obtained from single culture by E. mundtii WX1, respectively. This study provides the foundations for practical applications of coculture in bioconversion of lignocellulose particularly glucose-xylose-rich corn stover to l-LA.

Dual Microbial Inoculation, a Game Changer? – Bacterial Biostimulants With Multifunctional Growth Promoting Traits to Mitigate Salinity Stress in Spring Mungbean

Soil microbes play a vital role in improving plant growth, soil health, ameliorate biotic/abiotic stress and enhance crop productivity. The present study was aimed to investigate a coordinated effect of compatible consortium [salt tolerating Rhizobium and rhizobacterium with 1-aminocyclopropane-1-carboxylate (ACC) deaminase] in enhancing plant growth promoting (PGP) traits, symbiotic efficiency, nutrient acquisition, anti-oxidative enzymes, grain yield and associated profitability in spring mungbean. We identified a non-pathogenic compatible Rhizobium sp. LSMR-32 (MH644039.1) and Enterococcus mundtii LSMRS-3 (MH644178.1) from salt affected areas of Punjab, India and the same were assessed to develop consortium biofertilizer based on salt tolerance, multifarious PGP traits, antagonistic defense activities and presence of nifH, acds, pqq, and ipdc genes. Indole Acetic acid (IAA), P-solubilization, biofilm formation, exo-polysaccharides, siderophore, salt tolerance, ACC deaminase activities were all found highly significant in dual inoculant (LSMR-32 + LSMRS-3) treatment compared to LSMR-32 alone. Under saline soil conditions, dual inoculant showed a higher seed germination, plant height, biomass, chlorophyll content and macro and micro-nutrient uptake, than un-inoculated control. However, symbiotic (nodulation, nodule biomass and leghaemoglobin content) and soil quality parameters (phosphatase and soil dehydrogenase enzymes) increased numerically with LSMR-32 + LSMRS-3 over Rhizobium sp. LSMR-32 alone. Dual bacterial inoculation (LSMR-32 + LSMRS-3) increased the proline content (2.05 fold), anti-oxidative enzymes viz., superoxide dismutase (1.50 fold), catalase (1.43 fold) and peroxidase (3.88 folds) in contrast to control treatment. Decreased Na+ accumulation and increased K+ uptake resulted in favorable K+/Na+ ratio through ion homeostasis. Co-inoculation of Rhizobium sp. LSMR-32 and Enterococcus mundtii LSMRS-3 significantly improved the grain yield by 8.92% and led to superior B: C ratio over Rhizobium sp. alone under salt stress. To best of our knowledge this is perhaps the first field report from Indian soils that largely describes dual inoculation of Rhizobium sp. LSMR-32 and Enterococcus mundtii LSMRS-3 and the same can be considered as a game-changer approach to simultaneously induce salt tolerance and improve productivity in spring mungbean under saline stress conditions.

Enterococcus mundtii Isolated from Slovak Raw Goat Milk and Its Bacteriocinogenic Potential

Enterococci are lactic acid bacteria. Most of them can adapt well to the food system due to their salt and acid-tolerance. Moreover, many enterococcal species have been found to produce antimicrobial substances of proteinaceous character, i.e., bacteriocins/enterocins. In this study, Enterococcus mundtii EM ML2/2 with bacteriocinogenic potential was identified in Slovak raw goat milk. This strain demonstrated inhibition activity against up to 36% of Gram-positive indicator bacteria, and in concentrated form the bacteriocin substance (pH 6.3) showed the highest inhibition activity (1600 AU/mL) against the principal indicator strain E. avium EA5. Semi-purified substance (SPS) EM ML2/2 produced inhibition activity up to 3200 AU/mL. Concentrated bacteriocin substance and SPS maintained active (inhibition activity up to 100 AU/mL) for three months under −20 °C storage conditions. The strain showed susceptible antibiotic profile, and it did not form biofilm. No production of damaging enzymes was noted. It was nonhemolytic, as well as DNase, and gelatinase-negative. It grew well in skim milk, and it was salt and acid-tolerant. The bacteriocin potential of E. mundtii species isolated from Slovak raw goat milk has not previously been detected, so this is an original contribution which may stimulate addtitional research and application studies.

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. In our previous study, QU25 exhibited apparent CCR in a glucose-xylose mixture phenotypically, and transcriptional repression of the xylose operon encoding initial xylose metabolism genes, likely occurred in a CcpA-dependent manner. QU25 did not exhibit CCR phenotypically in a cellobiose-xylose mixture. The aim of the current study is to elucidate the transcriptional change associated with the simultaneous utilization of cellobiose and xylose. To this end, we performed RNA-seq analysis in the exponential growth phase of E. mundtii QU25 cells grown in glucose, cellobiose, and/or xylose as either sole or co-carbon sources. Our transcriptomic data showed that the xylose operon was weakly repressed in cells grown in a cellobiose-xylose mixture compared with that in cells grown in a glucose-xylose mixture. Furthermore, the gene expression of talC, the sole gene encoding transaldolase, is expected to be repressed by CcpA-mediated CCR. QU25 metabolized xylose without using transaldolase, which is necessary for homolactic fermentation from pentoses using the pentose-phosphate pathway. Hence, the metabolism of xylose in the presence of cellobiose by QU25 may have been due to 1) sufficient amounts of proteins encoded by the xylose operon genes for xylose metabolism despite of the slight repression of the operon, and 2) bypassing of the pentose-phosphate pathway without the TalC activity. Accordingly, we have determined the targets of genetic modification in QU25 to metabolize cellobiose, xylose and glucose simultaneously for application of the lactic fermentation from lignocellulosic hydrolysates.