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Aerobic metabolism and response to oxidative stress and starvation were studied in 11 Lactobacillus plantarum, L. paraplantarum and L. pentosus strains in order to assess the impact of aerobic metabolism on the growth and on the stress response. The strains were grown in aerobiosis without supplementation (AE), with hemin (AEH) or with hemin and menaquinone (AEHM) supplementation and in anaerobiosis (AN) in a complex buffered substrate. Growth rate, biomass yield, glucose and O consumption, production of lactic acid and HO, catalase activity, oxidative and starvation stress tolerance were evaluated. Aerobic growth increased biomass yield in late stationary phase. Further increase in yield was obtained with both hemin (H) and menaquinone (M) addition. With few exceptions, the increase in biomass correlated with the decrease of lactic acid which, however, decreased in anaerobic conditions as well in some strains. Addition of H or H + M increased growth rate for some strains but reduced the duration of the lag phase. HO production was found only for aerobic growth with no supplementation due to catalase production when hemin was supplemented. To our knowledge this is the first study in which the advantages of aerobic growth with H or H + M in improving tolerance of oxidative stress and long-term survival is demonstrated on several strains of the L. plantarum group. The results may have significant technological consequences for both starter and probiotic production. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) are used as starter or probiotic cultures in the food and pharmaceutical industries and, therefore, rapid and accurate methods for the detection of their viability are of practical relevance. In this study 10 LAB strains, belonging to the genera Enterococcus, Lactococcus, Leuconostoc, Lactobacillus, Streptococcus and Weissella, were subjected to heat and oxidative stresses and cell injury or death was assessed comparing different fluorescent probes (Syto 9; Propidium Iodide, PI; 4,6-diamidino-2-phenylindole, DAPI; 5,(6)-carboxyfluorescein diacetate, cFDA) to identify the stain combination which most reliably allowed the detection of live/metabolically active and dead cells. Protocols for specimen preparation and staining were optimized and a simple procedure for automated cell counts was developed using NIH ImageJ macros. Cysteine and semi-solid agar solution were efficiently used as anti-fading agent and mounting medium, respectively. The double staining cFDA-PI apparently offered the best and most versatile indication of both cell metabolic activity and membrane integrity. An excellent correlation between manual and automated cell counts for the majority of strain/stain combinations was found. This work provides a simple protocol for specimen preparation and staining based on the use of safe, easy to prepare and inexpensive reagents as compared to other methods. Additionally, the automated cell count procedure developed can be applied to several bacterial species and allows an increase in the number of experimental trials and the reproducibility and sensitivity of the analysis. [ABSTRACT FROM AUTHOR]

In previous studies we demonstrated that a relatively large diversity of stress response patterns (acid, osmotic, oxidative, heat) exists among Streptococcus thermophilus strains. Changes in protein expression, evaluated by SDS-PAGE in 4 wild strains (CNBL7035, TH681, Y3, Sfi39) and in three Sfi39 mutants in which hrcA, ctsR and rr01 genes were inactivated showed that significant variations of proteins involved in general stress response (GSR) occur as a function of growth phase, adaptation and inactivation of stress response regulators. In this work we re-evaluate the previous results comparing two unsupervised (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) and one supervised (Partial Least Square Regression, PLSR) statistical techniques for the ability to extract information from SDS-PAGE patterns of wild type and mutant strains of S. thermophilus and to uncover relationships between protein patterns and stress tolerance. HCA and PCA are two purely descriptive techniques. The HCA showed that SDS-PAGE is an efficient tool to differentiate strains but did not shed any light on the relationships between band intensity and strain, growth phase or adaptation treatment. PCA helped to identify group of bands which covaried with the stress input factors but also not allow to find a relationship between protein expression and stress tolerance. The PLS regression, even with the limitations due to the data set used in this study, appears as an extremely promising tools for the identification of complex relationships between design and response variables in the analysis of SDS-PAGE patterns of whole cell proteins. [ABSTRACT FROM AUTHOR]

Bacteriocins produced by lactic acid bacteria are a heterogeneous group of peptide inhibitors which include lantibiotics (class I, e.g. nisin), small heat-stable peptides (class II, e.g. pediocin AcH/PA1) and large heat-labile proteins (class III, e.g. helveticin J). Many bacteriocins belonging to the first two groups can be successfully used to inhibit undesirable microorganisms in foods, but only nisin is produced industrially and is licensed for use as a food preservative in a partially purified form. This review focuses on the production and purification of class I and class II bacteriocins from lactic acid bacteria. Bacteriocin production is growth associated but the yield of bacteriocin per unit biomass is affected by several factors, including the producing strain, media (carbohydrate and nitrogen sources, cations, etc.) and fermentation conditions (pH, temperature, agitation, aeration and dilution rate in continuous fermentations). Continuous fermentation processes with cell recycle or immobilized cells can result in a dramatic improvement in productivity over batch fermentations. Several simple recovery processes, based on adsorbing bacteriocin on resins or silica compounds, have been developed and can be used to build integrated production processes. [ABSTRACT FROM AUTHOR]

The influence of pH on growth, and lactic acid and bacteriocin production by Lactococcus lactis subsp. lactis 140 NWC was studied during batch fermentation in a lactose-based complex medium. Growth and lactic acid production were modelled using a simple logistic equation while substrate consumption was found to be a function growth and lactic acid production rate. The optimal pH for growth and lactic acid production was between 6.0 and 6.5. Bacteriocin production showed primary metabolite kinetics. pH had a dramatic effect on the production of the bacteriocin, lactococcin 140. A maximum activity of 15.4 × 10 AU (arbitrary units) 1 was obtained after 7 h at pH 5.5. Maximum bacteriocin activity was achieved before the end of growth and was followed by a decrease in activity, which was due to adsorption to the cells of the producing organism, possibly followed by degradation by specific proteases. Both bacteriocin production and degradation rates were higher at pH 5.0 and 5.5, resulting in sharper activity peaks than at pH 6.0 or 6.5. On the basis of the experimental results a qualitative model for bacteriocin production is proposed. [ABSTRACT FROM AUTHOR]

Fumaric acid production by Rhizopus arrhizus from potato flour was studied at different initial substrate concentrations (S), C/N ratios and fermentation times ( t f) in a composite design experiment. By using response surface methodology and canonical analysis, the experimental values of fumaric acid and mycelial biomass yields and productivity were fitted to the only statistically significant factors with mean percentage errors of 11, 26 and 13%, respectively. Owing to the limited statistical significance of the C/N ratio, it was possible to determine the values of S (25-50 g/l of glucose equivalent) and t f(44-100 h) associated with fumaric acid yields ranging from 60 to 75% and productivities varying from 6 to 8.4 g/l per day. Since such results were in quite good agreement with previous experiments carried out on other starchy materials, the above operating conditions might be used to minimize fumaric acid production costs as a function of the feed-stock used. [ABSTRACT FROM AUTHOR]

The prevalence of primary headache (PH) in a multiple sclerosis (MS) sample vs. control healthy subjects was investigated at a neurological clinic in 2004-2005: 122 of 238 (51%) MS patients and 57 of 238 (23%) controls proved to be affected by headache. The groups did not differ for the rates of PH types. Headache types of MS patients were comparable to those of PH patients that were observed at the same institute in a case-control comparison. First symptoms of headache preceded those of MS in two thirds of cases. Headache features did not significantly change after MS onset. Comorbidity of MS and PH could be explained by some common clinical and biological traits. [ABSTRACT FROM AUTHOR]