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γ-Aminobutyric acid (GABA) is a crucial neurotransmitter with wide application prospects. In this study, we focused on a GABA-producing strain from a traditional Chinese fermented beverage system. Among the six isolates, Lactobacillus hilgardii GZ2 exhibited the greatest ability to produce GABA in the traditional Chinese fermented beverage system. To increase GABA production, we optimized carbon sources, nitrogen sources, temperature, pH, and monosodium glutamate and glucose concentrations and conducted fed-batch fermentation. The best carbon and nitrogen sources for GABA production and cell growth were glucose, yeast extract and tryptone. Gradual increases in GABA were observed as the glucose and monosodium glutamate concentrations increased from 10 g/L to 50 g/L. During fed-batch fermentation, lactic acid was used to maintain the pH at 5.56, and after feeding with 0.03 g/mL glucose and 0.4 g/mL sodium glutamate for 72 h, the GABA yield reached 239 g/L. This novel high-GABA-producing strain holds great potential for the industrial production of GABA, as well as the development of health-promoting functional foods and medical fields. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the capacity of Lactobacillus hilgardii and Lactobacillus buchneri on modifying the bacterial community and improving fermentation and aerobic stability of high‐moisture corn (HMC). Methods and Results: High‐moisture corn was untreated (CTR), treated with L. hilgardii (LH) or L. buchneri (LB) at 600 000 CFU per gram fresh weight, or with L. hilgardii and L. buchneri at 300 000 CFU per gram fresh weight each (LHLB), and stored for 10, 30 or 92 days. Compared to CTR, inoculated silages had higher Lactobacillaceae relative abundance, lower yeasts numbers and higher aerobic stability. Treatment with LHLB resulted in a higher acetic acid concentration than LH and higher 1,2 propanediol concentration than LB, such differences were numerically greater at 10 and 30 days but statistically greater at 92 days. At 10 days, all inoculated silages were more stable than CTR, but LHLB was even more stable than LB or LH. Conclusions: The combination of L. hilgardii and L. buchneri had a synergistic effect on yeast inhibition, leading to greater improvements in aerobic stability as early as 10 days after ensiling. Significance and Impact of the Study: Lactobacillus hilgardii, especially in combination with L. buchneri, can improve the aerobic stability of HMC after a very short period of ensiling. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of inoculation of whole crop corn silage with a mixture of heterofermentative lactic acid bacteria (LAB) composed of Lactobacillus hilgardii and Lactobacillus buchneri on ensiling, aerobic stability, ruminal fermentation, total tract nutrient digestibility, and growth performance of beef cattle. Uninoculated control corn silage (CON) and silage inoculated with 3.0 × 105 cfu g−1 of LAB containing 1.5 × 105 cfu g−1 of L. hilgardii CNCM I-4785 and 1.5 × 105 cfu g−1 of L. buchneri NCIMB 40788 (INOC) were ensiled in silo bags. The pH did not differ (P > 0.05) between the two silages during ensiling but was greater (P < 0.001) for CON than INOC after 14 d of aerobic exposure (AE). Neutral detergent insoluble crude protein (NDICP) content (% of DM and % of CP basis) of terminal INOC silage was greater (P ≤ 0.05) than that of CON. In terminal silage, concentrations of total VFA and acetate were greater (P < 0.001), while water-soluble carbohydrates were lower (P < 0.001) for INOC than CON. Yeast and mold counts were lower for INOC than CON (P ≤ 0.001) in both terminal and aerobically exposed silages. The stability of INOC was greater (P < 0.001) than that of CON after 14 d of AE. Ruminal fermentation parameters and DMI did not differ (P > 0.05) between heifers fed the two silages, while there was a tendency (P ≤ 0.07) for lower CP and starch digestibility for heifers fed INOC than CON. Total nitrogen (N) intake and N retention were lower (P ≤ 0.04) for heifers fed INOC than CON. Dry matter intake as a percentage of BW was lower (P < 0.04) and there was a tendency for improved feed efficieny (G:F; P = 0.07) in steers fed INOC vs. CON silage. The NEm and NEg contents were greater for INOC than CON diets. Results indicate that inoculation with a mixture of L. hilgardii and L. buchneri improved the aerobic stability of corn silage. Improvements in G:F of growing steers fed INOC silage even though the total tract digestibility of CP and starch tended to be lower for heifers fed INOC are likely because the difference in BW and growth requirements of these animals impacted the growth performance and nutrient utilization and a greater proportion of NDICP in INOC than CON. [ABSTRACT FROM AUTHOR]

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BACKGROUND Lactic acid bacteria inocula have been developed over the years to improve the aerobic stability of silages. The aims of the study were to evaluate the effect of various conservation periods and the use of Lactobacillus hilgardii inoculum on aerobic stability, fermentative profile and microbial population of corn and sorghum silages. Trials were carried out on two corns and one sorghum crops. The crops were untreated or treated with L. buchneri (LB, application rate 300 000 cfu g−1 FM), L. hilgardii (LH, application rate 300 000 cfu g−1 FM) and a combination (LB + LH, application rate 150 000 cfu g−1 FM each). Silos were opened after 15, 30, 100 and 250 days of conservation, and the silages were analysed for fermentative profile, microbial count and aerobic stability. RESULTS: During conservation, the inocula influenced the fermentation profile. The use of LH increased the aerobic stability at 15 and 30 days in one out of three trials, while after 100 and 250 days, the presence of LB alone or with LH led to greater stability. In all the trials, the acetic acid content increased, the yeast count decreased and the aerobic stability increased during the conservation period. CONCLUSIONS: This study has shown that a long period in complete anaerobiosis reduced yeast count and improved aerobic stability in all silages. The addition of LB was confirmed to be a good option for increasing aerobic stability of silages, whereas the effect of LH alone or in combination with LB on aerobic stability was not consistent between trials. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The ensiling of sugarcane results in high dry-matter ( DM) loss, but the addition of glycerine may compensate for the loss during ensiling. Methanol is the most undesirable contaminant of crude glycerine destined for animal feeding. The aim of this study was to evaluate the ability of the yeast strain Pichia methanolica NCYC 1381 to reduce the methanol concentration in sugarcane silage inoculated with Lactobacillus hilgardii CCMA 0170 + glycerine. A randomized design consisted of four dose rates of glycerine (0, 4, 8 and 12% of fresh forage), three periods of silage fermentation (11, 34 and 68 d) and three combinations of microbial additives [ L. hilgardii ( LH), L. hilgardii plus P. methanolica ( LH + PM) and without microbial additive ( WI)]. The DM of the fresh sugarcane was 275 g kg−1. The linear reduction in neutral detergent fibre caused by glycerine inclusion was probably due to a dilution effect. The LH treatment increased the concentrations of the succinic, acetic and propionic acids, and 1,2-propanediol, and reduced the yeast population. The LH + PM treatment increased DM loss of sugarcane silage with 12% glycerine and L. hilgardii CCMA 0170 (6·1 log cfu g−1 of FM) reduced the DM loss when compared to the silage without additives. Under the conditions of the experiment, the P. methanolica treatment did not reduce the methanol concentration in silage. [ABSTRACT FROM AUTHOR]

Water kefir is a slightly alcoholic, lactic and acetic beverage fermented by yeasts, lactic acid bacteria and acetic acid bacteria that are associated with the polysaccharide of the water kefir grains. In this study, the three main metabolic products of microorganisms were evaluated during a traditional 192-h water kefir fermentation and also after inoculating the microorganisms in fresh medium or sterilised broth from different fermentation stages. The first process to occur was alcoholic fermentation, carried out in particular by Saccharomyces cerevisiae. After 24 h, lactic and acetic acid accumulation was generated by Lactobacillus hilgardii and Acetobacter tropicalis. By the end of fermentation, ethanol had been almost entirely consumed and oxidised to acetic acid, possibly by a dissimilatory route of Acetobacter species. An original hypothetical diagram is proposed for the carbon flux from sucrose, and the metabolic role of the main yeasts and bacteria is assigned for the distinct stages of water kefir fermentation. [ABSTRACT FROM AUTHOR]

Aerobic stability is an important feature in the evaluation of silages. The aims were to investigate the chemical and microbiological changes that occur in sugar-cane ( Saccharum spp.) silage after aerobic exposure, to identify the major species of yeasts associated with the aerobic deterioration process and to select lactic acid bacteria ( LAB) strains that can improve the aerobic stability of this silage. Fourteen wild LAB strains belonging to Lactobacillus plantarum, L. brevis and L. hilgardii were evaluated using experimental silos. Silage samples were collected at 0, 96 and 216 h after aerobic exposure to determinate the DM, WSC, p H, products of fermentation, to evaluate the silage temperatures and to identify yeast species associated with the aerobic deterioration of silage. The strains tested were able to modify the fermentative and chemical parameters and the diversity of yeasts species of silage after aerobic exposure. There was no association between the facultative or obligatory heterofermentative fermentation patterns and the increased aerobic stability of silage. Aerobic stability of sugar-cane silages was associated with high acetic acid and 1,2-propanediol concentrations. L. hilgardii UFLA SIL51 and UFLA SIL52 strains promoted an increase in aerobic stability of silage. [ABSTRACT FROM AUTHOR]

Aim To clone and characterize two related intracellular esterases from Oenococcus oeni and Lactobacillus hilgardii under wine-like conditions. Methods and Results The published genome sequences for O. oeni and Lact. hilgardii were used to identify, clone and purify putative esterase genes from these species designated EstCOo8 and EstC34, respectively. Both esterases are members of family V of lipolytic enzymes. However, EstC34 contains an SGSLG nucleophilic elbow structural motif instead of the usual GGSLG motif which is conserved in other lactic acid bacteria. Both esterases exhibited greatest specificity for C2-C4 pNP-linked substrates and retained activity under wine-like conditions. EstCOo8 had an optimum temperature, pH, and ethanol concentration of 40°C, 5·5 and 6% (v/v), respectively. Whereas EstC34 had an optimum temperature, pH and ethanol concentration of 50°C, 5·0 and 10% (v/v), respectively. Conclusions Both esterases were stable and retained activity under conditions that would be encountered in wine. They have the potential to reduce short-chain ethyl esters such as ethyl acetate. Significance and Impact of the Study This study provides information that might help improve the performance of LAB during malolactic fermentation in wine in the future, either by strain selection, optimization or direct enzyme addition. [ABSTRACT FROM AUTHOR]

The catabolic ornithine transcarbamylase (cOTC; EC 2.1.3.3) from the lactic acid bacteria Lactobacillus hilgardii is a key protein involved in the degradation of arginine during malolactic fermentation. cOTC containing an N-terminal His6 tag has been overexpressed in Escherichia coli, purified and crystallized under two different experimental conditions using the hanging-drop vapour-diffusion method. Crystals obtained from a solution containing 8%( w/ v) PEG 4000, 75 m M sodium acetate pH 4.6 belong to the trigonal space group P321 and have unit-cell parameters a = b = 157.04, c = 79.28 Å. Conversely, crystals grown in 20%( v/ v) 2-methyl-2,4-pentanediol, 7.5%( w/ v) PEG 4000, 100 m M HEPES pH 7.8 belong to the monoclinic space group C2 and have unit-cell parameters a = 80.06, b = 148.90, c = 91.67 Å, β = 100.25°. Diffraction data were collected in-house to 3.00 and 2.91 Å resolution for trigonal and monoclinic crystals, respectively. The estimated Matthews coefficient for the crystal forms were 2.36 and 2.24 Å3 Da−1, respectively, corresponding to 48% and 45% solvent content. In both cases, the results are consistent with the presence of three protein subunits in the asymmetric unit. The structure of cOTC has been determined by the molecular-replacement method using the atomic coordinates of cOTC from Pseudomonas aeruginosa (PDB code ) as the search model. [ABSTRACT FROM AUTHOR]

Aims: A contribution towards the elucidation of the mechanisms of tannins on bacteria growth inhibition, with particular focus on the interaction between tannins and bacterial proteins. Methods and results: The interaction between tannic acid (TA) and Lactobacillus hilgardii, a wine spoilage bacterium, was investigated by a combination of physiologic and proteomic approaches. Growing tests were performed on medium supplemented with TA at concentrations ranging from 100 to 1000 mg l−1 demonstrating the inhibitory effect of TA on the growth rate. Total proteins extracted from cells unexposed and exposed to TA were then analysed by 2D-electrophoresis and significant quantitative variations with a marked decrease of protein intensity upon TA exposure were observed. Most of the proteins, identified by ESI tandem Mass Spectrometry, were metabolic enzymes of different pathways, located in cytoplasm and membrane. Conclusions: The effects of TA on cells are deduced by the involvement of metabolic enzymes, and functional proteins on the tannin–protein interaction. These results might be related to the altered functions of the cell metabolism. Significance and impact of the study: The possible role of tannins in the inhibition of the bacterial survival and growth in a natural environment such as wine. A similar approach could be applied for evaluating the effects of tannins on food borne and pathogenic bacteria. [ABSTRACT FROM AUTHOR]