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PubMed2004

Effectiveness of acidic calcium sulfate with propionic and lactic acid and lactates as postprocessing dipping solutions to control Listeria monocytogenes on frankfurters with or without potassium lactate and stored vacuum packaged at 4.5 degrees C.

The safety of ready-to-eat meat products such as frankfurters can be enhanced by treating with approved antimicrobial substances to control the growth of Listeria monocytogenes. We evaluated the effectiveness of acidic calcium sulfate with propionic and lactic acid, potassium lactate, or lactic acid postprocessing dipping solutions to control L. monocytogenes inoculated (ca. 10(8) CFU/ml) onto the surface of frankfurters with or without potassium lactate and stored in vacuum packages at 4.5 degrees C for up to 12 weeks. Two frankfurter formulations were manufactured without (control) or with potassium lactate (KL, 3.3% of a 60% [wt/wt] commercially available syrup). After cooking, chilling, and peeling, each batch was divided into inoculated (four strains of L. monocytogenes mixture) and noninoculated groups. Each group was treated with four different dips: (i) control (saline solution), (ii) acidic calcium sulfate with propionic and lactic acid (ACS, 1:2 water), (iii) KL, or (iv) lactic acid (LA, 3.4% of a 88% [wt/wt] commercially available syrup) for 30 s. Noninoculated frankfurters were periodically analyzed for pH, water activity, residual nitrite, and aerobic plate counts (APCs), and L. monocytogenes counts (modified Oxford medium) were determined on inoculated samples. Surface APC counts remained at or near the lower limit of detection (<2 log CFU per frank) on franks with or without KL and treated with ACS or LA throughout 12 weeks at 4.5 degrees C. L. monoctogenes counts remained at the minimum level of detection on all franks treated with the ACS dip, which indicated a residual bactericidal effect when L. monocytogenes populations were monitored over 12 weeks. L. monocytogenes numbers were also reduced, but not to the same degree in franks made without or with KL and treated with LA. These results revealed the effectiveness of ACS (bactericidal effect) or LA (bacteriostatic effect) as postprocessing dipping solutions to inhibit or control the growth of L. monocytogenes on vacuum-packaged frankfurters stored at 4.5 degrees C for up to 12 weeks.

Animals↗
PubMed1995

Role of scalar protons in metabolic energy generation in lactic acid bacteria.

Lactic acid bacteria are able to generate a protonmotive force across the cytoplasmic membrane by various metabolic conversions without involvement of substrate level phosphorylation or proton pump activity. Weak acids like malate and citrate are taken up in an electrogenic process in which net negative charge is translocated into the cell thereby generating a membrane potential. The uptake is either an exchange process with a metabolic end-product (precursor/ product exchange) or a uniporter mechanism. Subsequent metabolism of the internalized substrate drives uptake and results in the generation of a pH gradient due to the consumption of scalar protons. The generation of the membrane potential and the pH gradient involve separate steps in the pathway. Here it is shown that they are nevertheless coupled. Analysis of the pH gradient that is formed during malolactic fermentation and citrate fermentation shows that a pH gradient, inside alkaline, is formed only when the uptake system forms a membrane potential, inside negative. These secondary metabolic energy generating systems form a pmf that consists of both a membrane potential and a pH gradient, just like primary proton pumps do. It is concluded that the generation of a pH gradient inside alkaline, upon the addition of a weak acid to cells is diagnostic for an electrogenic uptake mechanism translocating negative charge with the weak acid.

Cell Membrane↗
PubMed2005

Demineralization of red crab shell waste by lactic acid fermentation.

Lactic acid fermentation was applied to demineralize red crab shell waste using Lactobacillus paracasei subsp. tolerans KCTC-3074. Various concentrations (0, 2.5, 5.0, 10.0%) of glucose were supplemented as an initial carbon source and various amounts (2.5, 5.0, 10.0%) of the bacterial culture were inoculated as a starter. Microbial growth was very dependent on glucose concentration but little dependent on inoculum level. The pH decreased rapidly from pH 8 to pH 6 during the first day, at all three inoculum levels. At day 5 of fermentation, the 2.5, 5.0, and 10.0% inoculum levels with 10% glucose supply gave pH 5.5, 5.1, and 4.6, respectively, i.e. a decrease in pH concomitant with an increase in the inoculum level. The total titratable acidities (TTA) at day 5 for 2.5, 5.0, and 10.0% inoculum levels with 10% glucose supplement were 3.1, 4.5, and 8.3%, and the relative residual ash contents were 26.6, 25.9, and 19.0%, respectively. A negative relationship was found between pH and demineralization level (r2 = 0.8571), but there was a positive relationship between TTA and demineralization level (r2 = 0.5532).

Animals↗
PubMed2006

Proteolytic systems of lactic acid bacteria.

Lactic acid bacteria (LAB) have a very long history of use in the manufacturing processes of fermented foods and a great deal of effort was made to investigate and manipulate the role of LAB in these processes. Today, the diverse group of LAB includes species that are among the best-studied microorganisms and proteolysis is one of the particular physiological traits of LAB of which detailed knowledge was obtained. The proteolytic system involved in casein utilization provides cells with essential amino acids during growth in milk and is also of industrial importance due to its contribution to the development of the organoleptic properties of fermented milk products. For the most extensively studied LAB, Lactococcus lactis, a model for casein proteolysis, transport, peptidolysis, and regulation thereof is now established. In addition to nutrient processing, cellular proteolysis plays a critical role in polypeptide quality control and in many regulatory circuits by keeping basal levels of regulatory proteins low and removing them when they are no longer needed. As part of the industrial processes, LAB are challenged by various stress conditions that are likely to affect metabolic activities, including proteolysis. While environmental stress responses of LAB have received increasing interest in recent years, our current knowledge on stress-related proteolysis in LAB is almost exclusively based on studies on L. lactis. This review provides the current status in the research of proteolytic systems of LAB with industrial relevance.

Food Microbiology↗
PubMed1999

Safety of industrial lactic acid bacteria.

Lactic acid bacteria (LAB) are ubiquitous in fermented and non-fermented foods and are common components of the human commensal microflora. This long history of human exposure and consumption has led to the reasonable conclusion that they are generally safe. Recent attention has also focused on their possible role as probiotic bacteria, promoting beneficial health effects. There have, however, been a number of reports of human infections caused by LAB and these are reviewed. In most cases, the source of the infection was the commensal LAB flora rather than ingested bacteria and the patient had some underlying disease or predisposing condition. Even as opportunistic pathogens, the LAB, with the notable exception of the enterococci, are much less successful than a number of other members of the commensal microflora. The use of new strains for probiotic use is likely to require more detailed evidence for their safety, particularly if the strains have been genetically modified or have been derived from animals. Procedures that have been proposed for assessing the safety of new strains are described.

Endocarditis, Bacterial↗
PubMed2006

Comparative analysis of proteins with a mucus-binding domain found exclusively in lactic acid bacteria.

Lactic acid bacteria (LAB) are frequently encountered inhabitants of the human intestinal tract. A protective layer of mucus covers the epithelial cells of the intestine, offering an attachment site for these bacteria. In this study bioinformatics tools were used to identify and characterize proteins containing one type of mucus-binding domain, called MUB, that is postulated to play an important role in the adherence of LAB to this mucus layer. By searching in all protein databases 48 proteins containing at least one of these MUB domains in nine LAB species were identified. These MUB domains varied in size, ranging from approximately 100 to more than 200 residues per domain. Complete MUB domains were found exclusively in LAB. The number of MUB domains present in a single protein varied from 1 to 15. In some cases, orthologous proteins in closely related species contained a different number of domains, indicating that repeats of the domain undergo rapid duplication and deletion. Proteins containing the MUB domain were often encoded by gene clusters that encode multiple extracellular proteins. In addition to one or more copies of the MUB domain, many of these proteins contained other domains that are predicted to be involved in binding to and degradation of extracellular components. These findings strongly suggest that the MUB domain is an LAB-specific functional unit that performs its task in various domain contexts and could fulfil an important role in host-microbe interactions in the gastrointestinal tract.

Amino Acid Sequence↗
PubMed1999

Production of menaquinones by lactic acid bacteria.

Lactic acid bacteria were examined for their ability to produce quinone compounds, which may include dietary sources of menaquinones. Isoprenyl quinones in bacterial cells grown in a synthetic medium were extracted and analyzed by thin layer chromatography. Lactococcus lactis ssp. cremoris (three strains), Lactococcus lactis ssp. lactis (two strains), and Leuconostoc lactis were selected as high producers of quinone that synthesized more than 230 nmol of quinones/g of dried cells. The quinones were presumed to be menaquinone-7 to -10 by high performance liquid chromatography. Precise molecular weights were determined by mass spectrometry for Lactococcus lactis ssp. cremoris YIT 2011 and Leuconostoc lactis YIT 3001 and identified as menaquinone-8 and -9 for the former and menaquinone-9 and -10 for the latter. Those strains, when grown either in reconstituted nonfat dry milk or a soymilk medium, produced a beneficial quantity for dietary supplement (i.e., 29 to 123 micrograms of menaquinones/L of the fermented medium).

Benzoquinones↗
PubMed2005

Two-component signal transduction systems as key players in stress responses of lactic acid bacteria.

Lactic acid bacteria (LAB) continue as an important group of gram-positive bacteria that have been extensively exploited in food industries and various biotechnological applications. Some LAB species are, however, opportunistic pathogens and were reported to be associated with overwhelming number of human infections. During the use of LAB in industry or over the course of human infection, these bacteria are exposed to environmental stress. While LAB display adaptive mechanisms to cope with adverse conditions, the regulation of these mechanisms remains to be elucidated. Recent completion of genome sequencing of various LAB strains combined with the development of advanced molecular techniques have enabled the identification of a number of putative two-component signal transduction systems, also known as two-component regulatory systems (2CRS), in LAB. Examining the effect of deleting genes specifying putative 2CRS proteins in these organisms has revealed the involvement of 2CRS in the responses of LAB to different stresses. There are lines of evidence indicating that certain 2CRS may mediate a general stress response in Enterococcus faecalis and Streptococcus pyogenes. This review highlights the influence of 2CRS on the physiology of LAB during optimal growth and survival/growth on exposure to environmental stress.

Lactobacillaceae↗
PubMed1999

[Successful modification of human intestinal microflora with oral administration of lactic acid bacteria].

Lactic acid bacteria in food can transiently colonize the intestine and exert health beneficial (probiotic) effects. These include: 1. Lactose digestion, improvement of diarrheal disorders (including traveller's diarrhea), prophylaxis of intestinal and urogenital infections--as a result of formation or reconstruction of a balanced indigenous microflora. 2. Inhibition of the mutagenicity of the intestinal contents and reduction of the incidence of intestinal tumours. 3. Immunomodulatory effects resulting in the improved host resistance. 4. Depression of the serum cholesterol level. The most of these effects were observed in a group of adult subjects administered daily by a lyophilized Enterococcus faecium M-74 in the form of waffles (Dr. Ebi) during nine weeks of a double blind placebo controlled clinical trial. The bacterium temporarily colonized the host intestine and its secretion in stool persisted for six weeks after the last dose. The mean activities of beta-D-glucuronidase in stools of subjects given waffles containing enterococci were reduced comparing to stools of placebo subjects. After six weeks of daily eating the waffles with enterococci, an increased production of superoxide and other reactive oxygen intermediates by peripheral neutrophils was observed. The increase corresponded in time with an elevated formation of IgG by peripheral blood mononuclear cells after polyclonal activation with mitogenes. Higher activities of myeloperoxidase and elastase in peripheral neutrophils were also ascertained during eating of waffles containing of E. faecium M-74. Hence, intake of E. faecium M-74 in the form of waffles may have an significant immunostimulatory effect on both phagocytosis performed by neutrophils and antibody production. (Tab. 6, Ref. 29.)

Administration, Oral↗
PubMed2000

[Immunostimulatory and other beneficial health effects of lactic acid bacteria].

Lactic acid bacteria in functional foods can transiently colonize the intestine of man and exert beneficial probiotic effects. These were observed in a group of adult subjects administered daily by a lyophilized Enterococcus faecium M-74 in the form of waffles (Dr. Ebi) during nine weeks of a double blind placebo controlled clinical trial. The results showed significant immunostimulatory effect on both phagocytosis by neutrophils and antibody production.

Adjuvants, Immunologic↗
PubMed2002

[Food-grade gene expression systems for lactic acid bacteria].

Lactic acid bacteria (LAB) are important industrial microorganism used in the production and preservation of food-stuffs. Recently, considerable advances have been made in the genetics and molecular biology of LAB. These have resulted in the construction of food-grade gene expression systems for these bacteria. This paper aims to review the essential features for food-grade systems, food-grade selection markers, food-grade controlled gene expression and food-grade inducible signaling molecule, and recent developments on food-grade cloning and expression systems for LAB. These gene expression systems have great potential for studies on gene expression and regulation in LAB and a variety of bioprocessing application in industrial fermentations.

Food Industry↗
PubMed1986

Muscle fatigue and lactic acid accumulation.

Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement and insufficient supply of O2. During intense exercise sustained to fatigue muscle pH decreases to about 6.4-6.6. Force generation does not appear to be limited by the high H+ ion concentration per se but is more related to the PCr level. Phosphofructokinase may be inhibited by high H+ concentration but the inhibition is adequately overcome by increases in the activators AMP and ADP. A high concentration of H+ will decrease PCr by a direct effect on the creatine kinase equilibrium and indirectly by an increase in ADP. The effect of acidosis on glycolysis and on the PCr level will result in a decreased rate of ADP rephosphorylation, and it is suggested that ADP increases transiently above the steady-state level in the contracting muscle fibre. It is further suggested that the function of Na-K-ATPase is impaired by the increase of ADP resulting in an altered ionic balance over the muscle cell membrane. Muscle fatigue is thus considered to be due to an insufficient rate of ADP rephosphorylation resulting in a block in the activation process or in the excitation/contraction coupling.

Adenosine Triphosphate↗