Cyclic dipeptides from lactic acid bacteria inhibit the proliferation of pathogenic fungi

Lactobacillus plantarum LBP-K10 was identified to be the most potent antifungal strain from Korean traditional fermented vegetables. The culture filtrate of this strain showed remarkable antifungal activity against Ganoderma boninense. Five fractions from the culture filtrate were observed to have an inhibitory effect against G. boninense. Also, the electron ionization and chemical ionization indicated that these compounds might be cyclic dipeptides. Of the five active fractions, two fractions showed the most significant anti-Ganoderma activity, and one of these fractions inhibited the growth of Candida albicans. These compounds were identified to be cis-cyclo(l-Val-l-Pro) and cis-cyclo(l-Phe-l-Pro), as confirmed by X-ray crystallography.     

抑制黑色素合成的乳酸菌胞外多糖的筛选和性质研究

【目的】筛选可抑制黑色素合成的乳酸菌胞外多糖。【方法】通过观察凝乳拉丝外观筛选产胞外多糖的乳酸菌菌株,测量胞外多糖对B16黑色素瘤细胞黑色素合成和细胞活力的影响。对胞外多糖进行纯化,并通过PMP衍生-HPLC、红外光谱、抑制酪氨酸酶活性、抗氧化能力对其单糖组成和结构、作用机制进行研究。【结果】筛选到一株乳酸菌Lactobacillus rhamnosus HLAB122,发酵产生的胞外多糖在5 g/L浓度下可使B16细胞黑色素产量下降至空白对照的32.7%,且在96 h内对细胞活力无影响。纯化后的多糖由鼠李糖、葡萄糖、半乳糖构成,各单糖摩尔比为1?5.44?5.37。该胞外多糖不抑制酪氨酸酶活力且抗氧化性微弱。【结论】L.rhamnosus HLAB122产生的胞外多糖在个人护理产品中有潜在应用价值。     

Heteropolysaccharides from lactic acid bacteria

Microbial exopolysaccharides are biothickeners that can be added to a wide variety of food products, where they serve as viscosifying, stabilizing, emulsifying or gelling agents. Numerous exopolysaccharides with different composition, size and structure are synthesized by lactic acid bacteria. The heteropolysaccharides from both mesophilic and thermophilic lactic acid bacteria have received renewed interest recently. Structural analysis combined with rheological studies revealed that there is considerable variation among the different exopolysaccharides; some of them exhibit remarkable thickening and shear-thinning properties and display high intrinsic viscosities. Hence, several slime-producing lactic acid bacterium strains and their biopolymers have interesting functional and technological properties, which may be exploited towards different products, in particular, natural fermented milks. However, information on the biosynthesis, molecular organization and fermentation conditions is rather scarce, and the kinetics of exopolysaccharide formation are poorly described. Moreover, the production of exopolysaccharides is low and often unstable, and their downstream processing is difficult. This review particularly deals with microbiological, biochemical and technological aspects of heteropolysaccharides from, and their production by, lactic acid bacteria. The chemical composition and structure, the biosynthesis, genetics and molecular organization, the nutritional and physiological aspects, the process technology, and both food additive and in situ applications (in particular in yogurt) of heterotype exopolysaccharides from lactic acid bacteria are described. Where appropriate, suggestions are made for strain improvement, enhanced productivities and advanced modification and production processes (involving enzyme and/or fermentation technology) that may contribute to the economic soundness of applications with this promising group of biomolecules.     

Exploiting expolysaccharides from lactic acid bacteria

Microbial exopolysaccharides (EPSs) synthesized by lactic acid bacteria (LAB) play a major role in the manufacturing of fermented dairy products. EPS production is characterized by a large variety in terms of quantity, chemical composition, molecular size, charge, type of sidechains and rigidity of the molecules. Monosaccharide unit's composition, linkages, charge and size determine the EPS' intrinsic properties and their interactions with other milk constituents. EPSs contribute to texture, mouthfeel, taste perception and stability of the final product. Furthermore, it was reported that EPS from food grade organisms, particularly LAB, have potential as food additives and as functional food ingredients with both health and economic benefits. A better understanding of structure-function relationships of EPS in a dairy food matrix and of EPS biosynthesis remain two major challenges for further applications of EPS and the engineering of functional polysaccharides.     

Evaluation of lactic acid bacteria autolysate for the supplementation of lactic acid bacteria fermentation

At the end of culture in a carbon-limited medium, i.e. the best conditions for subsequent autolysis, lactic acid bacteria were harvested and autolysed at 50 °C for 24 h. The resulting supernatant was then successfully tested as a substitute for industrial yeast extract for the supplementation of whey permeate and its conversion into lactic acid: for almost equivalent total nitrogen amounts of both supplements, the same growth and production rates were recorded.     

乳酸菌发酵上清液成分分析

目的 乳酸菌发酵上清液为益生菌生产企业的废弃物,为了开发其在食品和饲料中的应用,对其进行初步的成分分析。 方法 采用本公司乳酸菌生产离心上清液为材料,用化学分析法测定其中的总固形物、总糖、总蛋白质和总酸等成分含量;采用抑菌圈法检测以大肠埃希菌为革兰阴性菌指示菌、金黄色葡萄球菌为革兰阳性菌指示菌的抑菌活性,并测定以大肠埃希菌为革兰阴性菌指示菌的抑菌效价;采用点样培养法测定菌种分泌淀粉酶、蛋白酶等消化酶的活力。 结果 乳酸菌发酵上清液分别含总固形物4.96%~7.04%、总糖0.11%~0.60%、总蛋白质1.67%~2.45%、总酸(以乳酸计)2.41~7.12 g/L;其对革兰阴性菌、革兰阳性菌都具有一定的抑制作用,抑菌效价范围为374.87~878.05 μ/g;测得菌种分泌淀粉酶活力(H/C)范围为4.33~8.67。 结论 初步揭示了乳酸菌发酵上清液中含有一定量的营养成分及抑菌活性、抑菌效价和淀粉酶活力,为开发其在食品和饲料中的应用提供了依据。     

Characterization of lactic acid bacteria isolated from seafood

Lactic acid bacteria were isolated from various samples of seafood: fresh pollock, brine shrimp, gravad fish, vacuum-packed seafood (surimi, smoked tuna, salted cod), and fish stored under 100% CO₂ at 5°C (smoked tuna, fresh and salted cod, salmon). Eighty-six independent isolates were obtained and were grouped according to cell morphology, presence or absence of diaminopimelic acid in the cell wall, and lactate configuration. Fifty-four isolates were identified as belonging to the genus Lactococcus and most of them exhibited DNA homologies with L. lactis subsp. lactis. Four strains were identified as Lactobacillus plantarum , eight strains as genus Leuconostoc and 16 belonged to the genus Carnobacterium. One facultative heterofermentative Lactobacillus and three other isolates were not identified. Of the strains 47% showed similar patterns of carbohydrate fermentations especially among strains belonging to the genera Lactococcus and Carnobacterium. Most of the strains (64%) grew at 5°C, in salted media and in fish extract medium without added sugar. Carnobacterium piscicola and Carn. divergens were the only reference strains able to grow in the same conditions as well as psychrotroph strains isolated from seafood. A numerical analysis could not be used because of the divergent properties of isolates of the same genus and strong similarities between different genera.     

Bifunctional thiosialosides inhibit influenza virus

We have synthesized a panel of bivalent S-sialoside analogues, with modifications at the 4 position, as inhibitors of influenza virus. These first generation compounds show IC₅₀ values ranging from low micromolar to high nanomolar in enzyme inhibition and plaque reduction assays with two intact viruses, Influenza H1N1 (A/California/07/2009) and H3N2 (A/Hongkong/8/68).     

Aldolases of the lactic acid bacteria

Reciprocal qualitative and quantitative immunological experiments employing an anti-Pediococcus cerevisiae aldolase serum confirmed many of the interspecific relationships demonstrated previously among lactic acid bacteria with antisera prepared against the Streptococcus faecalis fructose diphosphate aldolase. The extent of immunological relatedness observed between the Lactobacillus and Pediococcus aldolases was markedly greater than that noted between Pediococcus and Streptococcus aldolases indicating that the pediococci share closer phylogenetic ties with the rod-shaped lactobacilli than with their spherical counterparts in the streptococci. In addition to confirming the existence of definitive, but distant, relationships between the lactic acid bacteria and certain gram positive nonsporeforming anaerobes, immunological cross-reactivity was also demonstrated between the pediococcal aldolases and those of Aerococcus viridans.This paper is dedicated with deepest appreciation to Prof. Roger Y. Stanier on the occasion of his 60th birthday in token of what his friendship and guidance have meant to me. — J. L.     

Antimicrobial susceptibility of lactic acid bacteria isolated from a cheese environment

In the production of the Spanish traditional blue-veined Cabrales cheese, lactic acid bacteria strains free of antibiotic resistance that have a transferrable capacity are necessary as components of a specific starter. To select for these bacteria, the minimum inhibitory concentration (MIC) of 12 antibiotics and 2 mixtures (containing beta-lactamase inhibitor and penicillin) were determined by microbroth and agar dilution techniques in 146 strains belonging to the genera Lactococcus, Enterococcus, Lactobacillus, and Leuconostoc. The antibiotic-resistance profiles of Lactococcus and Enterococcus species were different from those of Lactobacillus and Leuconostoc, but clear genus- or species-associated patterns were not observed. Cefoxitin and metronidazole were not effective against bacteria of these genera. The MICs of beta-lactam antibiotics for lactobacilli and leuconostoc isolates were higher than those for lactococci and enterococci, but no strain was clinically resistant. All lactobacilli and leuconostoc isolates were resistant to high levels of vancomycin, a type of resistance not seen among the tested members of the genera Lactococcus and Enterococcus. The majority of the observed resistance appeared to be either intrinsic or nonspecific, although some strains of Lactococcus lactis, Enterococcus spp., and Lactobacillus spp. were resistant to antibiotics, such as chloramphenicol, erythromycin, clindamycin, or tetracycline.     

Health and nutritional benefits from lactic acid bacteria

Abstract There are several potential health or nutritional benefits possible from some species of lactic acid bacteria. Among these are: improved nutritional value of food, control of intestinal infections, improved digestion of lactose, control of some types of cancer, and control of serum cholesterol levels. Some potential benefits may result from growth and action of the bacteria during the manufacture of cultured foods. Some may result from growth and action of certain species of the lactic acid bacteria in the intestinal tract following ingestion of foods containing them. In selecting a culture to produce a specific benefit it is necessary to consider not only the wide variation among species of the lactic acid bacteria but also that among strains within a given species. With the possible exception of improving lactose utilization by persons who are lactose maldigestors, no specific health or nutritional claims can yet be made for the lactic acid bacteria.     

Health and nutritional benefits from lactic acid bacteria

There are several potential health or nutritional benefits possible from some species of lactic acid bacteria. Among these are: improved nutritional value of food, control of intestinal infections, improved digestion of lactose, control of some types of cancer, and control of serum cholesterol levels. Some potential benefits may result from growth and action of the bacteria during the manufacture of cultured foods. Some may result from growth and action of certain species of the lactic acid bacteria in the intestinal tract following ingestion of foods containing them. In selecting a culture to produce a specific benefit it is necessary to consider not only the wide variation among species of the lactic acid bacteria but also that among strains within a given species. With the possible exception of improving lactose utilization by persons who are lactose maldigestors, no specific health or nutritional claims can yet be made for the lactic acid bacteria.     

Comparative studies of lactic acid dehydrogenases in lactic acid bacteria

The stability, pH-dependence and kinetic properties of the Mn²⁺ and FDP-activated NAD-dependent lactic acid dehydrogenases from Lactobacillus casei ssp. casei (ATCC 393) and L. curvatus (DSM) 20010) were studied after the enzymes were purified to homogeneity by affinity chromatography. Both enzymes are virtually unidirectional, catalysing efficiently only the reduction of pyruvate. They are similar with respect to the effector requirement and pH-optimum. They differ, however, in their electrophoretic mobility, heat stability, pH-dependence of the Mn²⁺ requirement and several kinetic properties. It is suggested that most of these differences are caused by differences of the negative charges in the vicinity of the FDP-binding site or the site responsible for the interaction of the subunits of the enzymatically active oligomeres.Abbreviations l-LDH l-Lactic acid dehydrogenase - FDP Fructose-1,6-bisphosphate - DTE Dithioerythrol AddendumIn the case of the L. casei-LDH the shape of the NADH saturation curve is not changed by omitting the effectors FDP and Mn 2⁺. The K _M under these conditions is 3 fold higher (10.10 ^–5 M).     

Screening from pickled vegetables the potential probiotic strains of lactic acid bacteria able to inhibit the Salmonella invasion in mice

Aims: To screen from pickled vegetables the potential probiotic lactic acid bacteria (LAB) strains with antagonistic activity against Salmonella invasion in host. Methods and Results: Probiotic properties including acid and bile tolerance as well as inhibition on pathogenic bacteria were used for screening of LAB strains from pickled vegetables. Two strains, i.e Pediococcus pentosaceus MP12 and Lactobacillus plantarum LAP6, were selected and further assayed for their activities against Salmonella invasion in mouse liver and spleen. For these two LAB strains, strain LAP6 was able to adhere to the mouse intestinal epithelium cells. Conclusions: In screening of the probiotic strains able to inhibit the Salmonella invasion in host, factors other than the adherence to host intestinal epithelium may contribute some roles. Significance and Impact of the Study: Probiotic LAB strains with activity against Salmonella invasion in host could be isolated from vegetable origins. These strains may be used for vegetable processing.     

Class II antimicrobial peptides from lactic acid bacteria

Strains of lactic acid bacteria (LAB) produce a wide variety of antibacterial peptides. More than fifty of these so-called peptide bacteriocins have been isolated in the last few years. They contain 20-60 amino acids, and are cationic and hydrophobic in nature. Several of these bacteriocins consist of two complementary peptides. The peptide bacteriocins of LAB are inhibitory at concentrations in the nanomolar range, and cause membrane permeabilization and leakage of intracellular components in sensitive cells. The inhibitory spectrum is limited to gram-positive bacteria, and in many cases to bacteria closely related to the producing strain. Among the target organisms are food spoilage bacteria and pathogens such as Listeria, so that many of these antimicrobial peptides could have a potential as food preservatives as well as in medical applications.     

Bacteriocins of lactic acid bacteria

Lactic acid bacteria produce a variety of antagonistic factors that include metabolic end products, antibiotic-like substances and bactericidal proteins, termed bacteriocins. The range of inhibitory activity by bacteriocins of lactic acid bacteria can be either narrow, inhibiting only those strains that are closely related to the producer organism, or wide, inhibiting a diverse group of Gram-positive microorganisms. The following review will discuss biochemical and genetic aspects of bacteriocins that have been identified and characterized from lactic acid bacteria.     

乳酸菌的系统分类概况

乳酸菌是重要的益生菌资源,在食品、农业、化工业、医学等领域具有广阔的应用前景。目前,人们熟知的乳酸菌主要集中在乳杆菌属、双歧杆菌属、链球菌属、肠球菌属、乳球菌属、片球菌属和明串珠菌属等少数属种。为了拓宽人们对乳酸菌的认知,本文就乳酸菌的系统分类学进行阐述。在系统分类学上,乳酸菌分别隶属于厚壁菌门4纲7目18科39属653种和放线菌门2纲2目3科12属88种。最后,对乳酸菌的益生作用、安全性与有效来源、益生潜能的体外评价指标等进行简要的讨论。