Influence of autochthonous starter cultures on microbial dynamics and chemical-physical features of traditional fermented sausages of Basilicata region.

In this study, a combination of a Lactobacillus sakei strain and a Staphylococcus equorumstrain was used as autochthonous starter for an experimental production of Basilicata fermented sausages. The influence of starter addition on the safety and quality parameters and microbiological and chemical-physical properties of the products was investigated. Microbial counts of safety indicators were lower in the samples with the addition of starter culture, and, at the end of ripening, Enterobacteriaceae and Gram negative bacteria were detected only in samples made without the starter addition. The addition of starter led to a final product with better microbiological and chemical-physical features, and a positive effect on flavor and aroma compounds formation by a good proteolytic and lipolytic activities. The use of autochthonous starter cultures allows to obtain products with the organoleptic characteristics expected and steady in time and to standardize the production process, improving the safety and quality, but preserving the essential character of the product

Temperature and respiration affect the growth and stress resistance of Lactobacillus plantarum C17

Aims: The aim of the study is to gain further insight on the respiratory behaviour of Lactobacillus plantarum and its consequences on stress tolerance. Methods and Results: We investigated the effect of temperature and respiration on the growth and stress (heat, oxidative, freezing, freeze-drying) response of Lact. plantarum C17 during batch cultivations. Temperature as well as respiration clearly affected the physiological state of cells, and generally, cultures grown under respiratory conditions exhibited improved tolerance of some stresses (heat, oxidative, freezing) compared to those obtained in anaerobiosis. Our results revealed that the activities in cell-free extracts of the main enzymes related to aerobic metabolism, POX (pyruvate oxidase) and NPR (NADH peroxidase), were significantly affected by temperature. POX was completely inhibited at 37°C, while the activity of NPR slightly increased at 25°C, indicating that in Lact. plantarum, the temperature of growth may be involved in the activation and modulation of aerobic/respiratory metabolism. Conclusions: We confirmed that respiration confers robustness to Lact. plantarum cells, allowing a greater stress tolerance and advantages in the production of starter and probiotic cultures. Significance and Impact of the Study: This is the first study on respiratory metabolism on a strain other than the model strains WCFS1; novel information on the role of temperature in the modulation of aerobic/ respiratory metabolism in Lact. plantarum is presented

Effect of Respiratory Growth on the Metabolite Production and Stress Robustness of Lactobacillus casei N87 Cultivated in Cheese Whey Permeate Medium

Cheese whey permeate (WP) is a low-cost feedstock used for the production of biomass and metabolites from several lactic acid bacteria (LAB) strains. In this study, Lactobacillus casei N87 was cultivated in an optimized WP medium (WPM) to evaluate the effect of anaerobic and respiratory conditions on the growth performances (kinetics, biomass yield), consumption of sugars (lactose, galactose, glucose) and citrate, metabolite production [organic acids, volatile organic compounds (VOCs)] and stress survival (oxidative, heat, freezing, freeze-drying). The transcription of genes involved in the main pathways for pyruvate conversion was quantified through Real Time-PCR to elucidate the metabolic shifts due to respiratory state. Cultivation in WPM induced a diauxic growth in both anaerobic and respiratory conditions, and L. casei N87 effectively consumed the lactose and galactose present in WPM. Genomic information suggested that membrane PTS system and tagatose-6-P pathway mediated the metabolism of lactose and galactose in L. casei N87. Respiration did not affect specific growth rate and biomass production, but significantly altered the pyruvate conversion pathways, reducing lactate accumulation and promoting the formation of acetate, acetoin and diacetyl to ensure the redox balance. Ethanol was not produced under either cultivation. Pyruvate oxidase (pox), acetate kinase (ack), alpha-acetolactate decarboxylase (ald), acetolactate synthase (als) and oxaloacetate decarboxylase (oad) genes were up-regulated under respiration, while L-lactate dehydrogenase (ldh), pyruvate formate lyase (pfl), pyruvate carboxylase (pyc), and phosphate acetyltransferase (pta) were down regulated by oxygen. Transcription analysis was consistent with metabolite production, confirming that POX-ACK and ALS-ALD were the alternative pathways activated under aerobic cultivation. Respiratory growth affected the production of volatile compounds useful for the development of aroma profile in several fermented foods, and promoted the survival of L. casei N87 to oxidative stresses and long-term storage. This study confirmed that the respiration-based technology coupled with cultivation on low-cost medium may be effectively exploited to produce competitive and functional starter and/or adjunct cultures. Our results, additionally, provided further information on the activation and regulation of metabolic pathways in homofermentative LAB grown under respiratory promoting conditions

Growth and bacteriocin production by Enterococcus faecium DPC1146 in batch and continuous culture

Production of the bacteriocin enterocin 1146 (E1146) by Enterococcus faecium DPC1146 was studied in batch and continuous fermentation. Growth was strongly inhibited by lactic acid. In batch fermentations maximum E1146 activity (2.8 MBU L-1) was obtained in 9 h with 20 g L-1 glucose. Increase in initial glucose concentration did not lead to a proportional increase in E1146 activity. A simple linear model was found to be adequate to explain the relationship between specific bacteriocin production rate and specific growth rate in batch fermentations with initial glucose concentration higher than 20 g L-1. Maximum bacteriocin activity (2.9-3.2 MBU L-1) was obtained in continuous fermentations at dilution rates between 0.12 and 0.17 h-1 and specific bacteriocin production rate increased linearly with dilution rate

Evaluation of a differential medium for the preliminary identification of members of the Lactobacillus plantarum and Lactobacillus casei groups

A medium originally developed for differential enumeration of probiotic species in fermented milk (mMRS-BPB, Lee and Lee 2008) was evaluated for its ability to correctly discriminate members of the Lactobacillus plantarum (L. plantarum) and L. casei groups from other species. The medium was tested on 461 strains of lactic acid bacteria (LAB) belonging to eight genera and thirty-five species. Colony morphology was relatively consistent for L. plantarum, L. paraplantarum, L. pentosus, L. paracasei, L. casei, and L. rhamnosus, but, when used alone, was not always sufficient to discriminate these species from other species potentially present in cheese. A procedure based on tree classification was developed to obtain preliminary identification on the basis of colony morphology, cell morphology, and CO2 production from glucose. By combining results of the tree classification procedure and heuristic rules, correct preliminary identification at the species or group level could be obtained in 74.4 % of cases overall, and the percentage of correct identifications was as high as 88-100 % for members of the L. plantarum and L. casei groups. When species belonging to groups that can be easily discriminated by rapid molecular methods were combined, the decision tree allowed to correct identification at the group level for the 95 % of the strains. Logistic regression was used to evaluate the effect of strain, operator, light source, and incubation temperature. Although all factors significantly affected one or more of the characters used for identification, the classification procedure proved to be quite robust. It may be difficult to use mMRS-BPB in the differential enumeration of LAB in cheese, except when species composition is relatively simple; however, it can be used as a simple tool to guide molecular identification in studies focused on the isolation of new strains from cheese

Functional properties of Lactobacillus plantarum strains: A multivariate screening study

Abstract Thirty-two Lactobacillus plantarum strains isolated from different sources were genetically characterized at subspecies level with recA gene based multiplex PCR and pulsed-field electrophoresis. All the strains were tested in vitro for functional properties (ability to form biofilms, agglutination of yeast cells, bile salt hydrolase activity, β-galactosidase activity, surface hydrophobicity, resistance to lysozyme, gastric juice and bile salts), for antimicrobial activity and for antibiotic resistance. The presence of bsh and msa genes and of the pln bacteriocin loci were also evaluated. Hierarchical cluster analysis was used to identify eight different plantaritypes sharing similar patterns of pln loci. A global functional score was calculated by transforming values for continuous in vitro functional properties in an ordinal scale by cluster analysis, while a nominal scale was used for the other properties. Multidimensional scaling was used to evaluate the similarity in functional properties among the isolates and to evaluate the relationships between source of isolation and functional properties. Nine strains showed the best in vitro functional potential and a significant relationship was found between source of isolation and functional score. This study confirmed a high heterogeneity in functional properties among L. plantarum strains and provides insight for optimal screening strategies

Polymorphisms in stress response genes in Lactobacillus plantarum: implications for classification and heat stress response

The polymorphism of 5 stress response genes (hrcA, ctsR, clpP, ftsH, dnaK) in 32 Lactobacillus plantarum strains was evaluated by multilocus restriction typing (MLRT) and by sequence analysis of ctsR, hrcA and clpP genes. Both these approaches allowed the discrimination of the subspecies L. plantarum ssp. plantarum and L. plantarum ssp. argentoratensis. HrcA sequence analysis also allowed discrimination at the species and subspecies level of several species of lactic acid bacteria, thus confirming that it can be used as a valuable taxonomic marker. No significant relationship was found between stress response gene polymorphism and resistance to heat treatments. The effect of temperature on growth kinetics and the protein expression were investigated for selected strains carrying different mutations in hrcA. L. plantarum ssp. argentoratensis NCIMB12120 and L. plantarum ssp. plantarum DPC2159, both of which had mutations in domains of HrcA which are important for the repressor functionality, had a reduced growth rate at all temperatures tested (25, 30, 37, 40, and 42 °C) compared to L. plantarum WCFS1. In L. plantarum DPC2159, protein expression upon temperature shifts from 25 to 40 °C or growth at 40 °C was altered compared to L. plantarum WCFS1, but further study is needed to unequivocally confirm the relationship with mutations in hrcA

sclerostin levels in uremic patients a link between bone and vascular disease

AbstractSclerostin is a marker of low-turnover bone disease in end stage renal disease patients. The aim of this study was to evaluate serum sclerostin in uremic patients, analyzing its behavior during a single hemodialysis session. Twenty-one adult patients on intermittent hemodialysis treatment were enrolled. Acetate Free Bio-filtration (AFB) was the technique employed. Uremic patients were characterized by higher levels of serum sclerostin when compared with values observed in healthy subjects. Sclerostin assessed in pre-dialysis samples was 1.4 ± 1.02 ng/mL, whereas, in post dialysis samples, a reduction of sclerostin values was observed (0.8 ± 0.6 ng/mL; p: 0.008). Sclerostin correlated with parameters of dialysis adequacy, such as creatinine levels and Kt/V values, and it was significantly associated with atherosclerotic disease. Receiver operating characteristics analysis revealed a good diagnostic profile in identifying atherosclerotic disease. Sclerostin, a full dialyzable substance during AFB di..

Do changes in Lactuca sativa metabolic performance, induced by mycorrhizal symbionts and leaf UV-B irradiation, play a role towards tolerance to a polyphagous insect pest?

: The increased ultraviolet radiation (UV) due to the altered stratospheric ozone leads to multiple plant physiological and biochemical adaptations, likely affecting their interaction with other organisms, such as pests and pathogens. Arbuscular mycorrhizal fungi (AMF) and UV-B treatment can be used as eco-friendly techniques to protect crops from pests by activating plant mechanisms of resistance. In this study, we investigated plant (Lactuca sativa) response to UV-B exposure and Funneliformis mosseae (IMA1) inoculation as well as the role of a major insect pest, Spodoptera littoralis. Lettuce plants exposed to UV-B were heavier and taller than non-irradiated ones. A considerable enrichment in phenolic, flavonoid, anthocyanin, and carotenoid contents and antioxidant capacity, along with redder and more homogenous leaf color, were also observed in UV-B-treated but not in AMF-inoculated plants. Biometric and biochemical data did not differ between AMF and non-AMF plants. AMF-inoculated plants showed hyphae, arbuscules, vesicles, and spores in their roots. AMF colonization levels were not affected by UV-B irradiation. No changes in S. littoralis-feeding behavior towards treated and untreated plants were observed, suggesting the ability of this generalist herbivore to overcome the plant chemical defenses boosted by UV-B exposure. The results of this multi-factorial study shed light on how polyphagous insect pests can cope with multiple plant physiological and biochemical adaptations following biotic and abiotic preconditioning