Pulsed Electric Field treatment after malolactic fermentation of Tempranillo Rioja wines: Influence on microbial,physicochemical and sensorial quality

During wine stabilization, control of the microbial population is required in order to ensure a quality wine. Pulsed Electric Field (PEF) was applied to commercial wines in a continuous flow to reduce the amount of SO₂ added after the end of malolactic fermentation to manage microbial populations. Samples of wine from three commercial wineries of the Rioja Qualified Designation of Origin were treated with 30 mg/L SO₂, with 15 mg/L SO₂ and PEF, and only with PEF. The inactivation of the microbiota with the PEF treatment was greater than the inactivation achieved with SO₂ four days after treatment. Six months later, the lactic acid bacteria population was still viable in some of the wines. Regarding the physicochemical characterization of the wines, the PEF treatment was positive for quality because the wines had greater color intensity and lower volatile acidity. Moreover, organoleptic analysis indicated different scoring depending mainly on the characteristics of the original wine. Despite these positive results, further studies are advisable to optimize the control of lactic acid bacteria.Industrial relevanceThe application of PEF during wine stabilization after MLF can be a viable alternative for the oenological industry to reduce the SO₂ dosage used in winemaking.     

Studies on an inhibitor produced by lactic acid bacteria of wines on the control of malolactic fermentation

Malolactic fermentation is the microbiological process in wines, where lactic acid bacteria (LAB) govern the process of converting L-malic acid into L-lactic acid. During this process a high microbial load of LAB may lead to an unwanted spoilage phenomena by formation of excessive amounts of undesirable flavor compounds. This study is mainly focused on the isolation of LAB from the native flora of the wine, which has an inhibitory potential against malolactic activity of LAB inherent in wines. An isolate of Leuconostoc mesenteroides subsp. cremoris was found to produce an inhibitory compound against the LAB of wines. This compound was found to be a bacteriocin-like inhibitory substance (BLIS), which has a molecular weight of 32,000 Da, and it was shown that this BLIS was effective in the control of malolactic fermentation.     

Selection of lactic acid bacteria for use in vegetable fermentations

The fermentation of brined vegetables traditionally has depended upon growth of naturally occurring lactic acid bacteria to metabolize the vegetable sugars to organic acids which, together with added salt, results in preservation. Starter cultures have been used only to a limited extent commercially. However, recent efforts to improve fermentation vessels and to develop controlled fermentation methods for fermented vegetables has resulted in an increased interest in developing cultures suitable for application in such methods. Rapid and dominant growth, type and extent of acid production, salt tolerance, temperature range, CO₂ production, cell sedimentation, bacteriophage resistance, nutritional value, and ability to survive as concentrated cultures are factors to consider in developing lactic acid bacterial cultures for use in controlled fermentation of vegetables. Recent examples of efforts to improve cultures include development of nonmalate-decarboxylating strains of lactobacilli for use in cucumber fermentation and isolation of a new species of lactobacillus that produces only the L-isomer of lactic acid from the glucose for use in sauerkraut fermentation. Further improvements in starter cultures for fermented vegetables are likely when suitable genetic transfer systems are developed for selective incorporation or deletion of specific traits.     

Differentiation of mixed lactic acid bacteria communities in beverage fermentations using targeted terminal restriction fragment length polymorphism

Lactic acid bacteria (LAB) are an important group of bacteria in beer and wine fermentations both as beneficial organisms and as spoilage agents. However, sensitive, rapid, culture-independent methods for identification and community analyses of LAB in mixed-culture fermentations are limited. We developed a terminal restriction fragment length polymorphism (TRFLP)-based assay for the detection and identification of lactic acid bacteria and Bacilli during wine, beer, and food fermentations. This technique can sensitively discriminate most species of Lactobacillales, and most genera of Bacillales, in mixed culture, as indicated by both bioinformatic predictions and empirical observations. This method was tested on a range of beer and wine fermentations containing mixed LAB communities, demonstrating the efficacy of this technique for discriminating LAB in mixed culture.     

Occurrence of lactic acid bacteria and biogenic amines in biologically aged wines

Biologically aged sherry-type wines are elaborated by the so-called 'criadera and solera' system, which essentially involves development of the yeast on the wine surface forming a film velum for several years. Lactic acid bacteria can also develop and contribute to sherry-type wine quality, although their presence and role in this enological process have received very little attention. In this study, lactic acid bacteria microbiota and the presence of biogenic amines were investigated throughout the manufacture and biological aging of 36 samples of sherry wines. Malolactic fermentation was found to mainly take place during the first stage of biological ageing. The incidence and populations of lactic acid bacteria in sherry wines were low. The diversity of bacterial species isolated from the wines was greater than previously reported and included species of Lactobacillus, with prevailing Lactobacillus hilgardii, Lactobacillus plantarum and Lactobacillus zeae and Leuconostoc mesenteroides. The biogenic amine-producing capacity of the isolates was also determined. Five strains were putrescine producers, while another strain was shown to produce tyramine and phenylethylamine, simultaneously. L. zeae was one of the predominant species in wines during the biological aging and seemed to be one of the main putrescine producers. The biogenic amine composition of the wines investigated was similar to that reported for other types of wines. Putrescine was the major amine, followed by cadaverine, histamine and tyramine. The amine contents detected were lower than those usually reported in red wines.     

Influence of alcoholic and malolactic starter cultures on bioactive amines in Merlot wines

The influence of alcoholic and malolactic fermentations on the levels of amines in Merlot wines was investigated. Saccharomyces bayanus, S. cerevisiae, Lactobacillus plantarum, Oenococcus oeni (DSM 7008 and 12923) and spontaneous fermentations were used. Four of the 10 amines investigated were detected: spermidine, serotonin, putrescine and cadaverine. When considering the factors independently, the malolactic bacteria significantly affected the levels of serotonin and total amines, whereas the fermentation yeasts significantly affected the levels of spermidine (two way Kruskal–Wallis, p ? 0.05). Spermidine levels were significantly higher in wines produced with S. cerevisiae. Significantly higher serotonin levels were found in wines made with L. plantarum. Putrescine and cadaverine were not detected in wines produced by spontaneous alcoholic fermentation or by L. plantarum. There were significant differences in alcohol content, total and volatile acidity, sulphite levels and taste quality among wines (Tukey test, p ? 0.05).     

Intraspecific genetic diversity of lactic acid bacteria from malolactic fermentation of Cencibel wines as derived from combined analysis of RAPD-PCR and PFGE patterns

Three molecular techniques, randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), pulsed field gel electrophoresis (PFGE) and differential display-polymerase chain reaction (DD-PCR) have been used to assess the intraspecific diversity of the lactic microbiota responsible for spontaneous malolactic fermentation (MLF) in Cencibel wines made at a cellar in Castilla-La Mancha (Spain). The results indicate that RAPD-PCR and PFGE are of value in typing this microbiota. Better discrimination was achieved by RAPD-PCR. Reproducibility using DD-PCR was not good, which makes this method unsuitable. Combined numerical analysis of the patterns obtained from RAPD-PCR and PFGE allowed a better discrimination; this would therefore be a suitable tool to discriminate the diversity of bacterial communities like those found in MLF of wines. Genetic diversity data from combined numerical analysis suggest that there is considerable microbial diversity within MLF of Cencibel wines, with some genotypes coinciding in the two vinifications analysed.     

野生猕猴桃酒苹果酸-乳酸发酵优良乳酸菌的筛选与耐受性研究

该研究通过形态观察及生理生化试验,采用酸性番茄（ATB）培养基从自然启动苹果酸-乳酸发酵（MLF）的野生猕猴桃酒中筛选MLF优良乳酸菌,并对其SO2、酒精、pH耐受性进行测定。结果表明,经初筛得到6株乳酸菌,分别编号为R6、R7、R11、R14、R15、R18。其中,菌株R6、R15可耐受SO2 80 mg/L,菌株R7可耐受SO2 100 mg/L;菌株R6、R7可耐受酒精度14%vol,菌株R15可耐受酒精度12%vol;菌株R6、R7可耐受pH 3.2,菌株R15可耐受pH 3.0。综合分析,菌株R6、R7和R15具有较强的SO2、酒精及pH耐受能力,为MLF优良乳酸菌。     

干酪加工中的牛奶内源酶和非发酵剂乳酸菌

介绍了干酪加工中起作用的牛奶内源酶及微生物，包括血浆酶、组织蛋白酶D、半胱氨酸蛋白酶、脂蛋白脂肪酶和非发酵剂乳酸菌及它们的作用机制和特性。     

Identification of subdominant sourdough lactic acid bacteria and their evolution during laboratory-scale fermentations

Presumptive lactic acid bacterial cocci were found in six sourdoughs (out of 20) from the Abruzzo region (central Italy) and subjected to phenotypic and genotypic characterization. A total of 21 isolates, recognized as seven strains by randomly amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR) typing, were identified by a polyphasic approach, consisting of 16S rRNA gene sequencing, multiplex PCR assays and physiological features, as Enterococcus faecium and Pediococcus pentosaceus. Four strains belonging to those species and previously isolated from wheat kernels were inoculated in sterile flour to verify their capacity to grow in sourdough environment. Doughs with several dual bacterial combinations, including Lactobacillus sanfranciscensis, were propagated for 11 days and pH measurements and bacterial counts were carried out.     

Added pentosans in breadmaking: fermentations of derived pentoses by sourdough lactic acid bacteria

One hundred and seventy strains of sourdough lactobacilli were screened for their capacity to grow optimally by using pentoses. Lb. alimentarius M106 and M137, Lb. hilgardii S32, Lb. brevis AM11, Lb. fermentum I4 and Lb. brevis AM8 had a higher cell yield, growth rate and acetic acid production on a mix of arabinose, xylose or ribose and maltose than on maltose as carbon sources. In the cofermentation process, pentoses were preferentially consumed instead of maltose. Pentosan extract was treated with α-L-arabinofuranosidase from Aspergillus niger or endo-xylanase from Bacillus subtilis to produce hydrolysates respectively each of arabinose and xylose. Depending on the type of pentose and other unidentified compounds, hydrolysates specifically substantiated the growth and acetic acid production of sourdough lactobacilli. Sourdough fermentation by Lb. hilgardii S32 with addition of pentosans and endo-xylanase enzyme increased the acidification rate, titratable acidity, acetic acid content and cell yield number. In addition to the well known role in retarding bread staling, pentosans may also be used as sources of pentoses which favour the performances of selected sourdough lactobacilli.     

Practical implications of lactate and pyruvate metabolism by lactic acid bacteria in food and beverage fermentations

This article reviews the metabolism of pyruvate and lactate by lactic acid bacteria (LAB) involved in food and beverage fermentations with an emphasis on practical implications. First, the formation of pyruvate and lactate from a range of substrates, including carbohydrates, organic acids and amino acids, is briefly described. The catabolism of pyruvate and lactate by LAB is then reviewed. This is followed by a discussion of lactate degradation and racemisation by LAB from specific fermented foods and beverages. Finally, the impact of environmental factors and metabolic engineering on pyruvate and lactate metabolism by LAB is evaluated with regard to practical significance.     

Probiotic spectra of lactic acid bacteria (LAB)

Lactic acid bacteria (LAB) and their probio-active cellular substances exert many beneficial effects in the gastrointestinal tract. LAB prevent adherence, establishment, and replication of several enteric mucosal pathogens through several antimicrobial mechanisms. LAB also release various enzymes into the intestinal lumen and exert potential synergistic effects on digestion and alleviate symptoms of intestinal malabsoption. Consumption of LAB fermented dairy products with LAB may elicit antitumor effects. These effects are attributed to the inhibition of mutagenic activity; decrease in several enzymes implicated in the generation of carcinogens, mutagens, or tumor-promoting agents; suppression of tumors; and the epidemiology correlating dietary regimes and cancer. Specific cellular components in LAB strains seem to induce strong adjuvant effects including modulation of cell-mediated immune responses, activation of reticuloendothelial system, augmentation of cytokine pathways and regulation of interleukins, and tumor necrosis factors. Oral administration of LAB is well tolerated and proven to be safe in 143 human clinical trials and no adverse effects were reported in any of the total 7,526 subjects studied during 1961-1998. In an effort to decrease the reliance on synthetic antimicrobials and control the emerging immunocompromised host population, the time has come to carefully explore the prophylactic and therapeutic applications of probiotic LAB.     

Spontaneous organic cocoa bean box fermentations in Brazil are characterized by a restricted species diversity of lactic acid bacteria and acetic acid bacteria

Spontaneous organic cocoa bean box fermentations were carried out on two different farms in Brazil. Physical parameters, microbial growth, bacterial species diversity [mainly lactic acid bacteria (LAB) and acetic acid bacteria (AAB)], and metabolite kinetics were monitored, and chocolates were produced from the fermented dry cocoa beans. The main end-products of the catabolism of the pulp substrates (glucose, fructose, and citric acid) by yeasts, LAB, and AAB were ethanol, lactic acid, mannitol, and/or acetic acid. Lactobacillus fermentum and Acetobacter pasteurianus were the predominating bacterial species of the fermentations as revealed through (GTG)₅-PCR fingerprinting of isolates and PCR-DGGE of 16S rRNA gene PCR amplicons of DNA directly extracted from fermentation samples. Fructobacillus pseudoficulneus, Lactobacillus plantarum, and Acetobacter senegalensis were among the prevailing species during the initial phase of the fermentations. Also, three novel LAB species were found. This study emphasized the possible participation of Enterobacteriaceae in the cocoa bean fermentation process. Tatumella ptyseos and Tatumella citrea were the prevailing enterobacterial species in the beginning of the fermentations as revealed by 16S rRNA gene-PCR-DGGE. Finally, it turned out that control over a restricted bacterial species diversity during fermentation through an ideal post-harvest handling of the cocoa beans will allow the production of high-quality cocoa and chocolates produced thereof, independent of the fermentation method or farm.     

Effects of SO2 on lactic acid bacteria physiology when used as a preservative compound in malolactic fermentation

SO₂ is a preservative compound widely used at an industrial scale to control the cider‐making processes. However, little is known about the effect that sulfur dioxide exerts on the cell physiology of lactic acid bacteria (LAB) during malolactic fermentation, taking into account the cellular heterogeneity of the microbial populations. Analysis of flow cytometry results has shown how increasing SO₂ concentrations were not related to a significant rise in the dead cell subpopulation. SO₂ affected malolactic activity and cell viability, giving rise to different levels of LAB tolerance to the fermentation conditions. Malate consumption in the bioreactor and the enzymatic potential of whole cells were monitored during the bioconversion process under the different assayed conditions. After SO₂ exposure, specific malolactic activity of whole cells measured by enzymatic assays in which SO₂ or other inhibitory compounds were absent showed higher values than the malolactic activity determined in the bioreactor, suggesting that inhibition was not irreversible, at least not at the concentrations tested. A correlation between total malolactic activity and viable and viable but nonculturable cell concentrations was established. Increasing amounts of SO₂ in the fermentation media also affected the malic acid/lactic acid ratio. Changes observed on LAB physiology at different sulfiting levels could be useful for practical cider‐making applications. Copyright © 2012 The Institute of Brewing & Distilling     

Malolactic fermentation of Tempranillo wine: contribution of the lactic acid bacteria inoculation to sensory quality and chemical composition

Malolactic fermentation (MLF) of Tempranillo Rioja wines (Spain) inoculated with two lactic acid bacteria (LAB) strains were studied and compared with spontaneous MLF. Inoculation with selected Oenococcus oeni lyophila shortened MLF duration up to 19 days and lead to wines with more fresh and fruity characters, especially when implantation was 100%. We demonstrated modifications in the concentration of volatile and nitrogenous compounds and a good correlation between analytical and sensory attributes was also noted. In addition, the low initial amino acid concentration and the consumption of these compounds by the inoculated yeast strain during alcoholic fermentation resulted in wines with very low biogenic amines levels (under 3.75 mg L^?1) after MLF and 3 month storage period in all cases. The results showed the significance of choose the most suitable starter to elaborate quality wines and suggest the control of amino acid content in must and wine to prevent the formation of biogenic amines.     

臭豆腐乳酸菌多样性及耐酸乳酸菌的筛选分离

对采集的8个不同地区的臭豆腐样品中的乳酸菌多样性分析表明,臭豆腐中乳酸菌数量在6.8×104cfu/g～2.9×106cfu/g,优势乳酸菌包括乳杆菌、乳球菌和肠球菌.通过乳酸菌耐酸特性比较,表明不同来源样品中乳酸菌耐酸差异性不明显,而不同种类乳酸菌的耐酸差异性较明显,肠球菌耐酸性比例高,乳杆菌其次,乳球菌最低.经筛选获得pH 3.0、37℃培养6 h后存活率超过30%的菌株6株,对其中2株耐酸最强的杆菌和球菌进行鉴定,分别为植物乳杆菌和屎肠球菌.