相关论文
2020 - Science Translational Medicine
Metabolic reprogramming of donor T cells enhances graft-versus-leukemia effects in mice and humans

Bicarbonate boosts metabolic fitness of T cells challenged with leukemia-derived lactic acid. A basic treatment for leukemia For patients with acute myeloid leukemia, hematopoietic stem cell transplant offers a chance of curing the underlying cancer, in part because of the graft-versus-leukemia effect, or anticancer activity of transplanted T cells. Unfortunately, this does not always work, and engrafted T cells often fail to control the leukemia. By studying patients with acute myeloid leukemia who relapsed after hematopoietic stem cell transplant, Uhl et al. found that lactic acid produced by leukemic cells specifically interfered with T cell activity. The detrimental effects of lactic acid could be overcome with sodium bicarbonate, which improved T cell metabolic fitness in both mouse models and human patients. Acute myeloid leukemia (AML) relapse after allogeneic hematopoietic cell transplantation (allo-HCT) has a dismal prognosis. We found that T cells of patients relapsing with AML after allo-HCT exhibited reduced glycolysis and interferon-γ production. Functional studies in multiple mouse models of leukemia showed that leukemia-derived lactic acid (LA) interfered with T cell glycolysis and proliferation. Mechanistically, LA reduced intracellular pH in T cells, led to lower transcription of glycolysis-related enzymes, and decreased activity of essential metabolic pathways. Metabolic reprogramming by sodium bicarbonate (NaBi) reversed the LA-induced low intracellular pH, restored metabolite concentrations, led to incorporation of LA into the tricarboxylic acid cycle as an additional energy source, and enhanced graft-versus-leukemia activity of murine and human T cells. NaBi treatment of post–allo-HCT patients with relapsed AML improved metabolic fitness and interferon-γ production in T cells. Overall, we show that metabolic reprogramming of donor T cells is a pharmacological strategy for patients with relapsed AML after allo-HCT.

2000 - Applied and Environmental Microbiology
Isolation and Expression of Lactate Dehydrogenase Genes from Rhizopus oryzae

ABSTRACT Rhizopus oryzae is used for industrial production of lactic acid, yet little is known about the genetics of this fungus. In this study I cloned two genes, ldhA and ldhB, which code for NAD+-dependent l-lactate dehydrogenases (LDH) (EC 1.1.1.27 ), from a lactic acid-producing strain of R. oryzae. These genes are similar to each other and exhibit more than 90% nucleotide sequence identity and they contain no introns. This is the first description of ldh genes in a fungus, and sequence comparisons revealed that these genes are distinct from previously isolated prokaryotic and eukaryotic ldh genes. Protein sequencing of the LDH isolated from R. oryzae during lactic acid production confirmed that ldhA codes for a 36-kDa protein that converts pyruvate to lactate. Production of LdhA was greatest when glucose was the carbon source, followed by xylose and trehalose; all of these sugars could be fermented to lactic acid. Transcripts fromldhB were not detected when R. oryzae was grown on any of these sugars but were present when R. oryzae was grown on glycerol, ethanol, and lactate. I hypothesize thatldhB encodes a second NAD+-dependent LDH that is capable of converting l-lactate to pyruvate and is produced by cultures grown on these nonfermentable substrates. BothldhA and ldhB restored fermentative growth toEscherichia coli (ldhA pfl) mutants so that they grew anaerobically and produced lactic acid.

2016 - Lwt - Food Science and Technology
Survival of probiotic lactic acid bacteria immobilized in different forms of bacterial cellulose in simulated gastric juices and bile salt solution

Abstract In this work, we discuss the possibilities of using bacterial cellulose (BC) produced by Gluconacetobacter xylinus as carrier support for the immobilization of probiotic strains of Lactobacillus spp. In our study, immobilization of the microorganisms was performed by the adsorption of bacterial cells on the surface of the synthetized BC and by a simultaneous cultivation of the probiotic bacteria with cellulose-synthetizing G. xylinus . Co-cultures were conducted in stationary cultures, in which BC was synthesized as pellicles on the medium surface and in shaken cultures in which BC was synthetized in the forms of beads. The experiments carried out also included the analysis of the survival of immobilized probiotic bacteria in the presence of gastric juices and bile salts solution. The results showed that immobilization of probiotic Lactobacillus in BC during co-culture with G. xylinus was the most effective immobilization method, providing high-level protection of the microorganisms against the influence of gastric juices and bile salts.

1964 - Applied microbiology
EFFECT OF WATER EXTRACTS OF CAROB PODS, TANNIC ACID, AND THEIR DERIVATIVES ON THE MORPHOLOGY AND GROWTH OF MICROORGANISMS.

The effect of aqueous extracts of carob (Ceratonia siliqua) pods, gallotannic acid, gallic acid, and catechol on several microorganisms was studied. Carob pod extract and tannic acid showed a strong antimicrobial activity toward some cellulolytic bacteria. On the basis of tannin content, to which antimicrobial effect was related, carob pod extracts inhibited Cellvibrio fulvus and Clostridium cellulosolvens at 15 mug/ml, Sporocytophaga myxococcoides at 45 mug/ml, and Bacillus subtilis at 75 mug/ml. The inhibiting concentrations for tannic acid were found to be 12, 10, 45, and 30 mug/ml, respectively. Gallic acid and catechol were much less effective. Tannic acid and the tannin fraction of carob extract exerted both bacteriostatic and bactericidal effects on C. fulvus. Respiration of C. fulvus in the presence of bactericidal concentrations of tannic acid or tannin fraction of carob extract was inhibited less than 30%. A partial formation of "protoplasts" by C. fulvus was obtained after 2 hr of incubation in a growth medium to which 20% sucrose, 0.15% MgSO(4).7H(2)O, and 10 to 50 mug/ml of tannic acid or 500mug/ml of penicillin, or both, had been added. Tannic acid and the tannin fraction of carob extract protected C. fulvus from metabolic lysis in sucrose solution. Although the growth of other microorganisms tested was only slightly affected, the morphology of some of them was drastically changed in the presence of subinhibitory concentrations of carob pod extracts of tannic acid. It is suggested that the site of action of tannins on sensitive microorganisms is primarily the cell envelope.

2006 - Current issues in intestinal microbiology
Lactic acid bacteria as probiotics.

A number of Lactobacillus species, Bifidobacterium sp, Saccharomyces boulardii, and some other microbes have been proposed as and are used as probiotic strains, i.e. live microorganisms as food supplement in order to benefit health. The health claims range from rather vague as regulation of bowel activity and increasing of well-being to more specific, such as exerting antagonistic effect on the gastroenteric pathogens Clostridium difficile, Campylobacter jejuni, Helicobacter pylori and rotavirus, neutralising food mutagens produced in colon, shifting the immune response towards a Th2 response, and thereby alleviating allergic reactions, and lowering serum cholesterol (Tannock, 2002). Unfortunately, most publications are case reports, uncontrolled studies in humans, or reports of animal or in vitro studies. Whether or not the probiotic strains employed shall be of human origin is a matter of debate but this is not a matter of concern, as long as the strains can be shown to survive the transport in the human gastrointestinal (GI) tract and to colonise the human large intestine. This includes survival in the stressful environment of the stomach - acidic pH and bile - with induction of new genes encoding a number of stress proteins. Since the availability of antioxidants decreases rostrally in the GI tract production of antioxidants by colonic bacteria provides a beneficial effect in scavenging free radicals. LAB strains commonly produce antimicrobial substance(s) with activity against the homologous strain, but LAB strains also often produce microbicidal substances with effect against gastric and intestinal pathogens and other microbes, or compete for cell surface and mucin binding sites. This could be the mechanism behind reports that some probiotic strains inhibit or decrease translocation of bacteria from the gut to the liver. A protective effect against cancer development can be ascribed to binding of mutagens by intestinal bacteria, reduction of the enzymes beta-glucuronidase and beta-glucosidase, and deconjugation of bile acids, or merely by enhancing the immune system of the host. The latter has attracted considerable interest, and LAB have been tested in several clinical trials in allergic diseases. Characteristics ascribed to a probiotic strain are in general strain specific, and individual strains have to be tested for each property. Survival of strains during production, packing and storage of a viable cell mass has to be tested and declared.

2009 - Biotechnology and bioengineering
Understanding and harnessing the microaerobic metabolism of glycerol in Escherichia coli

Given its availability, low prices, and high degree of reduction, glycerol has become an ideal feedstock for the production of reduced compounds. The anaerobic fermentation of glycerol by Escherichia coli could be an excellent platform for this purpose but it requires expensive nutrients such as tryptone and yeast extract. In this work, microaerobic conditions were used as a means of eliminating the need for rich nutrients. Availability of low amounts of oxygen enabled redox balance while preserving the ability to synthesize reduced products. A fermentation balance analysis showed ∼95% recovery of carbon and reducing equivalents. The pathways involved in glycerol dissimilation were identified using different genetic and biochemical approaches. Respiratory (GlpK‐GlpD/GlpABC) and fermentative (GldA‐DhaKLM) routes mediated the conversion of glycerol to glycolytic intermediates. Although pyruvate formate‐lyase (PFL) and pyruvate dehydrogenase contributed to the synthesis of acetyl‐CoA from pyruvate, most of the carbon flux proceeded through PFL. The pathways mediating the synthesis of acetate and ethanol were required for the efficient utilization of glycerol. The microaerobic metabolism of glycerol was harnessed by engineering strains for the co‐production of ethanol and hydrogen (EH05 [pZSKLMgldA]), and ethanol and formate (EF06 [pZSKLMgldA]). High ethanol yields were achieved by genetic manipulations that reduced the synthesis of by‐products succinate, acetate, and lactate. Co‐production of hydrogen required the use of acidic pH while formate co‐production was facilitated by inactivation of the enzyme formate‐hydrogen lyase. High rates of product synthesis were realized by overexpressing glycerol dehydrogenase (GldA) and dihydroxyacetone kinase (DhaKLM). Engineered strains efficiently produced ethanol and hydrogen and ethanol and formate from glycerol in a minimal medium without rich supplements. Biotechnol. Bioeng. 2009;103: 148–161. © 2008 Wiley Periodicals, Inc.

1959
Muscular Fatigue and Mortality in Troll-Caught Chinook Salmon (Oncorhynchus tshawytscha)

Blood samples were analyzed for lactic acid from 66 troll caught chinook salmon after from zero to 103/4 hours of rest. Fish were held in a live box aboard a trolling vessel. During the course of the experiment 22 individuals died. Analysis of these data indicate a general response of blood lactic acid comparable with results of other experiments. The typical response is a gradual increase of blood lactic acid to high levels in the third and fourth hours, followed by a general decline. Death is strongly associated with high blood lactic acid. The level of lactic acid response is not significantly increased with more than 10 minutes of vigorous exercise nor is it significantly affected by the size of the fish within the ranges sampled in this experiment. Mortality rate is estimated at 71% with 95 percent binomial confidence limits of 40% and 86%.

1997 - Separation Science and Technology
Separation of fermentation products by membrane techniques. I. Separation of lactic acid/lactates by diffusion dialysis

Abstract The results of the separation of lactic acid from sodium lactate by diffusion dialysis are presented in this paper. Neosepta AFN-7 and Selemion DSV membranes were used for the separation. The dialytic separation factor for lactic acid/sodium lactate was found to be ∼20 for Neosepta AFN-7 and ∼30 for Selemion DSV membranes. The fluxes inherent in the separation were up to ∼1 mol/m2·h for the acid and only up to ∼0.07 mol/m2·h for the salt. The effects that enable the separation, i.e., the differences in solubility and diffusivity of the acid and the salt, were estimated (single solute experiments). The partition coefficients for lactic acid were found close to or above unity whereas those for sodium lactate were much lower. On the contrary, the apparent diffusion coefficients of both solutes were comparable, being of the order of 10−11 m2/s. It results that the separation of the weak acid and salt is based on differences in solubilities rather than in diffusivities, i.e., the phenomenon is differe...

2010 - Journal of Applied Microbiology
Determination of the shelf life of sliced cooked ham based on the growth of lactic acid bacteria in different steps of the chain

Aims:  Development of a predictive model for the determination of the shelf life of modified atmosphere‐packed (MAP) cooked sliced ham in each step of the cold chain.

1993 - Journal of food protection
Inactivation and Attachment of Listeria monocytogenes on Beef Muscle Treated with Lactic Acid and Selected Bacteriocins.

Cubical pieces (1 cm3) of aseptically obtained beef muscle were treated with lactic acid (2%), nisin (4 × 104 IU/ml) and pediocin PO2 (a bacteriocin produced by Pediococcus acidilactici PO2; 3.2 × 103 arbitrary units/ml). Treated meat was immersed for 1 min in a cell suspension of a mixture of two strains of Listeria monocytogenes and then stored for 48 h at 4°C. Meat cubes were analyzed immediately after immersion in the cell suspension, then after 1, 24, and 48 h of storage. Count of L. monocytogenes per cube and percentage of attached cells were determined. Data indicated that the antimicrobial agents significantly (p = 0.05) decreased the count of L. monocytogenes during the 48-h storage by 1.7, 1.1, and 0.6 log10 CFU/6 cm2 of meat surface for lactic acid, nisin, and pediocin PO2 treatments, respectively. Lactic acid on the meat surface had an immediate and also a delayed listericidal action, but bacteriocins only inhibited L. monocytogenes immediately, and had little or no delayed antilisterial effect. The percentage of Listeria cell attached to the beef muscle significantly (p = 0.05) increased in the presence of lactic acid, but the value did not change significantly or slightly decreased in the presence of nisin and pediocin PO2, respectively.

2006 - The American journal of clinical nutrition
Conversion of alpha-linolenic acid in humans is influenced by the absolute amounts of alpha-linolenic acid and linoleic acid in the diet and not by their ratio.

BACKGROUND Human in vivo data on dietary determinants of alpha-linolenic acid (ALA; 18:3n-3) metabolism are scarce. OBJECTIVE We examined whether intakes of ALA or linoleic acid (LA; 18:2n-6) or their ratio influences ALA metabolism. DESIGN During 4 wk, 29 subjects received a control diet (7% of energy from LA, 0.4% of energy from ALA, ALA-to-LA ratio = 1:19). For the next 6 wk, a control diet, a low-LA diet (3% of energy from LA, 0.4% of energy from ALA, ratio = 1:7), or a high-ALA diet (7% of energy from LA, 1.1% of energy from ALA, ratio = 1:7) was consumed. Ten days before the end of each dietary period, [U-13C]ALA was administered orally for 9 d. ALA oxidation was determined from breath. Conversion was estimated by using compartmental modeling of [13C]- and [12C]n-3 fatty acid concentrations in fasting plasma phospholipids. RESULTS Compared with the control group, ALA incorporation into phospholipids increased by 3.6% in the low-LA group (P = 0.012) and decreased by 8.0% in the high-ALA group (P < 0.001). In absolute amounts, it increased by 34.3 mg (P = 0.020) in the low-LA group but hardly changed in the high-ALA group. Nearly all ALA from the plasma phospholipid pool was converted into eicosapentaenoic acid. Conversion of eicosapentaenoic acid into docosapentaenoic acid and docosahexaenoic acid hardly changed in the 3 groups and was <0.1% of dietary ALA. In absolute amounts, it was unchanged in the low-LA group, but increased from 0.7 to 1.9 mg (P = 0.001) in the high-ALA group. ALA oxidation was unchanged by the dietary interventions. CONCLUSION The amounts of ALA and LA in the diet, but not their ratio, determine ALA conversion.

1991 - Journal of food protection
Microbiological Effects of Acid Decontamination of Beef Carcasses at Various Locations in Processing.

Hot (55°C), dilute (1% v/v) lactic acid was sprayed on beef carcass surfaces immediately after dehiding, after evisceration (immediately before chilling), or at both locations. Surface samples of carcasses were examined for total aerobic plate counts (APCs) and for the presence of Salmonella and Listeria . APCs of treated beef carcasses were lower (P<0.05) than those of control carcasses. APCs were determined both at slaughter day 0 (immediately after carcasses enter the chill room) and after 72 h postmortem. At day 0, reductions in log10 APC by more than 90% occurred when carcasses were treated with lactic acid after evisceration or both after dehiding and after evisceration. The effect of lactic acid decontamination was greatest on carcasses treated with lactic acid both after dehiding and after evisceration. No further reductions in APCs of carcasses were observed on samples taken 72 h postmortem. No difference in color between control and acid-treated carcasses was observed. All samples tested for the presence of Salmonella were negative. Listeria was detected in three samples from control carcasses only. Samples obtained from strip loins of acid-treated or control carcasses did not show any consistent pattern of differences in microbiological counts. Additional data collected from carcasses sprayed with lactic acid in three different sized slaughter plants showed that irrespective of differences in size of slaughter facility, mean APCs of acid-treated carcasses were significantly (P<0.05) lower than those of control carcasses.

2006 - Cell Cycle
Brave Little World: Spheroids as an in vitro Model to Study Tumor-Immune-Cell Interactions

Multicellular tumor spheroids (MCTS) are a well established 3-D in vitro model system that reflects the pathophysiological in vivo situation in tumor microregions and of avascular micrometastatic sites. Because monocytes and other immune cells infiltrate into MCTS of different origin, such spheroid co-cultures are a valuable, still underestimated tool to systematically study heterologous interactions between tumor and immune cells. The present article gives a brief overview on work that has been published on tumor - immune cell interactions in MCTS and also summarizes mechanisms of immune suppression in the tumor milieu focussing on myeloid cells. Using the co-culture model, we recently demonstrated that tumor-derived lactic acid is a potent modulator of human monocyte as lactic acid inhibited the differentiation of monocytes (MO) into dendritic cells (DC) and also impaired antigen presentation. We show herein, that the capacity of various tumor cells in MCTS to secrete lactic acid differs up to tenfold, suggesting that this capacity is dependent on the tumor cell type. It is further demonstrated that lactic acid disturbs the migration of MO into MCTS as infiltration could be increased by blocking lactic acid production. We therefore discuss lactic acid which accumulates in many tumors and tumor microregions as a potent immune suppressor for MO/DC in the tumor milieu and conclude that these data are highly relevant for adoptive immunotherapy protocols with DC.

2006 - Molecular plant-microbe interactions : MPMI
Organic acids, sugars, and L-tryptophane in exudates of vegetables growing on stonewool and their effects on activities of rhizosphere bacteria.

The influence of stonewool substrate on the exudation of the major soluble carbon nutrients and of the auxin precursor tryptophane for Pseudomonas biocontrol agents was studied. To this end, the composition of the organic acids and sugars, as well that of tryptophane, of axenically collected exudates of seed, seedlings, and roots of tomato, cucumber, and sweet pepper was determined. The major results were as follows. i) The total amount of organic acid is much higher than that of total sugar. ii) Exudation of both organic acids and sugars increases during plant growth. iii) Citric, succinic, and malic acids represent the major organic acids, whereas fructose and glucose are the major sugars. iv) Compared with glass beads as a neutral substrate, stonewool substantially stimulates exudation of organic acids and sugars. v) It appeared that enhanced root-tip-colonizing bacteria isolated previously from the rhizosphere of tomato and cucumber grow much better in minimal medium with citrate as the sole carbon source than other, randomly selected rhizobacteria do. This indicates that the procedure which selects for excellent root-tip colonizers enriches for strains which utilize the major exudate carbon source citrate. vi) The content of L-tryptophane, the direct precursor of auxin, is approximately 60-fold higher in seedling exudates of tomato and sweet pepper than in cucumber seedling exudates, indicating a higher possibility of plant growth stimulation after inoculation with auxin-producing rhizobacteria for tomato and sweet pepper crops than for cucumber. However, the biocontrol strain Pseudomonas fluorescens WCS365, which is able to convert tryptophane into auxin, did not stimulate growth of these three crops. In contrast, this strain did stimulate growth of roots of radish, a plant which exudes nine times more tryptophane than tomato does.

2006 - Bioresource technology
Lactic acid fermentation of food waste for swine feed.

This study was conducted to determine the effects of lactic acid bacteria (LAB, Lactobacillus salivarius) inoculation on the microbial, physical and chemical properties of food waste mixture (FWM) stored at ambient temperature (25 degrees C) for 10 and 30 days. A complete pig diet including restaurant food waste, bakery by-product, barley and wheat bran, and broiler poultry litter was amended with LAB at the levels of 0.1%, 0.2%, 0.5% and 1.0% and fermented anaerobically. These treatments were compared with intact FWM before storage and non-anaerobically stored FWM. Non-anaerobic storage of FWM showed microbial putrefaction with the loss (P < 0.05) of water and water soluble carbohydrate (WSC) and increases (P < 0.005) in protein and fiber. Anaerobic fermentation of FWM with or without LAB seemed effective in both 10- and 30-day-storage. The addition of LAB inoculants to FWM showed a linear trend (P < 0.05) toward an increase in the number of total and lactic acid bacteria and toward the nutritional improvement with WSC increased and fiber decreased. Long-term (30 days) storage resulted in consistent reduction (P < 0.05) in numbers of total and lactic acid bacteria and pH and showed little change in chemical components, compared with short-term (10 days) storage. On the basis of these results, LAB inoculation improved fermentative characteristics of FWM. Among anaerobic treatments, further WSC increase and NDF reduction did not occur (P > 0.05) when LAB-added levels were over 0.2%. Based on these observations the optimum level of LAB addition to FWM was 0.2%.

1965 - Journal of Dairy Science
VOLATILE FATTY ACIDS PRODUCED BY SOME LACTIC ACID BACTERIA. I. FACTORS INFLUENCING PRODUCTION OF VOLATILE FATTY ACIDS FROM CASEIN HYDROLYSATE.

Abstract The effect of several conditions of substrate on total and individual volatile fatty acids (VFA) produced from casein hydrolysate by resting cells of three strains of lactic streptococci and two strains of lactobacilli has been studied. Fatty acids were steam-distilled from the reaction mixture and total and individual VFA determined by titration with alkali and by gas chromatography. Optimum pH of substrate was in the neutral or slightly alkaline range. Optimum temperature of incubation was 32 C for streptococci and 42 C for lactobacilli. Shaking incubation was more favorable to production of VFA than static incubation. There was no appreciable difference in total VFA production between incubations with air and with nitrogen atmosphere. Addition of sodium caseinate to casein hydrolysate stimulated VFA production, whereas addition of lactose or milk fat showed a slight inhibitory effect. Patterns of individual VFA varied from strain to strain, depending on the conditions of substrate.

2014 - ACS Synthetic Biology
Modified Lactic Acid Bacteria Detect and Inhibit Multiresistant Enterococci

We designed Lactococcus lactis to detect Enterococcus faecalis. Upon detection, L. lactis produce and secrete antienterococcal peptides. The peptides inhibit enterococcal growth and reduce viability of enterococci in the vicinity of L. lactis. The enterococcal sex pheromone cCF10 serves as the signal for detection. Expression vectors derived from pCF10, a cCF10-responsive E. faecalis sex-pheromone conjugative plasmid, were engineered in L. lactis for the detection system. Recombinant host strains were engineered to express genes for three bacteriocins, enterocin A, hiracin JM79 and enterocin P, each with potent antimicrobial activity against E. faecalis. Sensitive detection and specific inhibition occur both in agar and liquid media. The engineered L. lactis also inhibited growth of multidrug-resistant E. faecium strains, when induced by cCF10. The presented vectors and strains can be components of a toolbox for the development of alternative antibiotic technologies targeting enterococci at the site of infection.

1994 - Fems Microbiology Reviews
Genetics of lactose utilization in lactic acid bacteria

: Lactose utilization is the primary function of lactic acid bacteria used in industrial dairy fermentations. The mechanism by which lactose is transported determines largely the pathway for the hydrolysis of the internalized disaccharide and the fate of the glucose and galactose moieties. Biochemical and genetic studies have indicated that lactose can be transported via phosphotransferase systems, transport systems dependent on ATP binding cassette proteins, or secondary transport systems including proton symport and lactose-galactose antiport systems. The genetic determinants for the group translocation and secondary transport systems have been identified in lactic acid bacteria and are reviewed here. In many cases the lactose genes are organized into operons or operon-like structures with a modular organization, in which the genes encoding lactose transport are tightly linked to those for lactose hydrolysis. In addition, in some cases the genes involved in the galactose metabolism are linked to or co-transcribed with the lactose genes, suggesting a common evolutionary pathway. The lactose genes show characteristic configurations and very high sequence identity in some phylogenetically distant lactic acid bacteria such as Leuconostoc and Lactobacillus or Lactococcus and Lactobacillus. The significance of these results for the adaptation of lactic acid bacteria to the industrial milk environment in which lactose is the sole energy source is discussed.

1988 - American Journal of Enology and Viticulture
Properties of Wine Lactic Acid Bacteria: Their Potential Enological Significance

Lactic acid bacteria isolated from Australian red wines were examined for properties of potential enological significance. Some 166 strains were tested. Strains of Leuconostoc oenos were divided into rough and smooth morphotypes on the basis of colony appearance. Rough morphotypes produced cells arranged in long chains and readily grew in wine. Smooth morphotypes produced cells arranged in pairs or short chains, but most of these strains exhibited poor growth in wine. As tested in API 50CH galleries (pH 6.0), strains of L. oenos, Pediococcus parvulus , and several Lactobacillus species exhibited considerable heterogeneity in their abilities to ferment carbohydrates. The fermentation profile of individual strains was altered when the pH was reduced to 4.0. Strains of L. oenos were more tolerant of low pH than those of P. parvulus or Lactobacillus spp. Strains of P. parvulus and Lactobacillus spp. were more tolerant of high concentrations of ethanol and total sulfur dioxide. None of the strains produced extracellular protease. Lipases were produced by several strains of L. oenos and one strain of Lactobacillus . The majority of strains produced esterases.

2006 - Applied and Environmental Microbiology
Antibiotic Resistances of Starter and Probiotic Strains of Lactic Acid Bacteria

ABSTRACT The antibiotic resistances of 45 lactic acid bacteria strains belonging to the genera Lactobacillus, Streptococcus, Lactococcus, Pediococcus, and Leuconostoc were investigated. The objective was to determine antibiotic resistances and to verify these at the genetic level, as is currently suggested by the European “qualified presumption of safety” safety evaluation system for industrial starter strains. In addition, we sought to pinpoint possible problems in resistance determinations. Primers were used to PCR amplify genes involved in β-lactam antibiotic, chloramphenicol, tetracycline, and erythromycin resistance. The presence of ribosomal protection protein genes and the ermB gene was also determined by using a gene probe. Generally, the incidences of erythromycin, chloramphenicol, tetracycline, or β-lactam resistances in this study were low (<7%). In contrast, aminoglycoside (gentamicin and streptomycin) and ciprofloxacin resistances were higher than 70%, indicating that these may constitute intrinsic resistances. The genetic basis for ciprofloxacin resistance could not be verified, since no mutations typical of quinolone resistances were detected in the quinolone determining regions of the parC and gyrA genes. Some starter strains showed low-level ampicillin, penicillin, chloramphenicol, and tetracycline resistances, but no known resistance genes could be detected. Although some strains possessed the cat gene, none of these were phenotypically resistant to chloramphenicol. Using reverse transcription-PCR, these cat genes were shown to be silent under both inducing and noninducing conditions. Only Lactobacillus salivarius BFE 7441 possessed an ermB gene, which was encoded on the chromosome and which could not be transferred in filter-mating experiments. This study clearly demonstrates problems encountered with resistance testing, in that the breakpoint values are often inadequately identified, resistance genes may be present but silent, and the genetic basis and associated resistance mechanisms toward some antibiotics are still unknown.

Heteropolysaccharides from lactic acid bacteria.

L De Vuyst
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L. Vuyst
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L. De Vuyst
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B Degeest
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B. Degeest

Abstract: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.

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