Caseinolytic proteases of Lactobacillus and Lactococcus strains isolated from fermented dairy products

Proteases of Lactobacillus and Lactococcus strains catalyze casein degradation in fermented dairy products, which can result in the production of bioactive peptides. Proteolytic properties of a selection of lactic acid bacteria (LAB) strains previously isolated in Croatia, including Lactococcus lactis and Lactobacillus strains, are described. All strains of Lactobacillus and Lactococcus showed an Fmc+ phenotype that can be associated with efficient growth in milk. The significant caseinolytic effect, after incubation of culture supernatant or concentrated cell biomass, was observed for Levilactobacillus brevis D6 and Lactiplantilactobacillus plantarum D13 after growth in the optimal growth medium, while for Lactoccocus lactis ZGBP5-32 and Levilactobacillus brevis SF9B strains after growth in skimmed milk. To assess the LAB growth in skimmed milk, the acidification rate was monitored. Statistically, significant acidification capacity was determined for L. plantarum D13 in the optimal medium and by the proteolytic strain Lactobacillus helveticus M92 in skimmed milk. After extraction of proteinases from the strains with caseinolytic activity, protein samples were analysed by the SDS-PAGE. The protein extract of the Lc. lactis ZGBP5-32 and ZGZA7-10, retained proteolytic activity even at very low concentrations. The ultrafiltration improved protein extraction. The crude extract possibly contained putative protease, as a decrease in contaminating proteins was confirmed by SDS-PAGE in samples of L. brevis D6 and SF9B, L. fermentum D12 and L. plantarum D13.

The state of water is associated with the viability and acidification capacity of Lactobacilli in frozen sourdough

The correlations between water state and the key factors affecting sourdough quality, including cell activity and acidification capacity of lactic acid bacteria (LAB), were established in this study. Results revealed that with the increase of frozen storage time, the cell density (CD), total titratable acidity (TTA), and organic acids content declined, whereas the pH value rose. Further, the freezable water content (FWC) and free water quantity (FWQ) decreased, but the total water loss rate (WLR) and immobilised water quantity (IWQ) increased. The CD showed a highly inversely correlation with WLR, and the pH value was strongly inversely correlated to the FWQ. The confocal laser scanning microscopy (CLSM) observed that the ice crystals had larger volumes during frozen storage. Our data, for the first time, disclosed that the total water content and the FWQ may play a crucial role in maintaining the viability and acidification capacity of LAB in frozen sourdough.

Technological Characterization of Lactic Acid Bacteria Isolated from Different Sheep’s Milk

Background: Technological characterization of lactic acid bacteria isolated from sheep’s milk collected in 3 regions in northwestern Algeria.Methods: During the period from 2018 to 2019, fifty strains of Lactic acid bacteria isolated from samples sheep’s milk were evaluated for several technologically-relevant properties: diacetyl and exopolysaccharides production, acidification, proteolytic and lipolytic activity and their antagonist activity against Escherichia coli and Pseudomonas aeruginosa. Result: The results indicate that among all the isolates only 20% were distinguished by their production of EPS mainly the genus Leuconostoc. Diacetyl production was observed in 71% of Lactobacillus, 60% of Enterococcus and 25% in Leuconostoc. 94% isolates showed moderate proteolytic activity. 56% and 60% of the strains degraded tween 80 and olive oil respectively for lipolytic activity. Inhibition activity by the cultures LAB was about 82% and 78% against E. coli and P. aeruginosa respectively. No culture supernatants inhibit P. aeruginosa, however 18% of the Enterococcus trains inhibit E. coli. BME1.A2 and BME2.D4 showed their highest acidification capacity developing a very large quantity of lactic acid after 24 h of incubation, i.e., 7.6 and 8.4 g lactic acid/L respectively.

Biodiversity and dairy traits of lactic acid bacteria from foliage of aromatic plants before and after dehydration process monitored by a smart sensors system

ABSTRACT The main hypothesis of this work was to evaluate the presence of lactic acid bacteria (LAB) intrinsically resistant to plant essential oils in sage (Salvia officinalis L.) and laurel (Laurus nobilis), for future applications in functional cheese production by addition of aromatic herbs. The effect of the drying process on the viability of LAB was evaluated with three biomass densities (3, 4 and 5 kg/m2). The drying densities did not affect weight loss, but influenced the levels of LAB of sage and laurel. A total of 10 different strains of Enterococcus faecium, Enterococcus mundtii, Enterococcus raffinosus and Leuconostoc mesenteroides were identified from laurel, while sage did not host any LAB species. In particular, L. mesenteroides was the only species sensitive to the heat treatment. Only five strains, all enterococci, were resistant to at least one antibiotic, even though no strain showed gelatinase or haemolytic activity. The investigation on the technological traits useful in cheese making demonstrated that all LAB can be considered non starter LAB, because they were characterized by a slow acidification capacity (the pH was still above 6.00 after 3 d) and a very limited autolysis (the maximum decrease of the optical density at 599 nm was barely 0.2).

Tubular Acidification Defect in Adults with Sickle Cell Disease

Background and objectivesMetabolic acidosis is a frequent manifestation of sickle cell disease but the mechanisms and determinants of this disorder are unknown. Our aim was to characterize urinary acidification capacity in adults with sickle cell disease and to identify potential factors associated with decreased capacity to acidify urine.Design, setting, participants, & measurementsAmong 25 adults with sickle cell disease and an eGFR of ≥60 ml/min per 1.73 m2 from a single center in France, we performed an acute acidification test after simultaneous administration of furosemide and fludrocortisone. A normal response was defined as a decrease in urinary pH <5.3 and an increase in urinary ammonium excretion ≥33 µEq/min at one or more of the six time points after furosemide and fludrocortisone administration.ResultsOf the participants (median [interquartile range] age of 36 [24–43] years old, 17 women), 12 had a normal and 13 had an abnormal response to the test. Among these 13 participants, nine had normal baseline plasma bicarbonate concentration. Plasma aldosterone was within the normal range for all 13 participants with an abnormal response, making the diagnosis of type 4 tubular acidosis unlikely. The participants with an abnormal response to the test were significantly older, more frequently treated with oral bicarbonate, had a higher plasma uric acid concentration, higher hemolysis activity, lower eGFR, lower baseline plasma bicarbonate concentration, higher urine pH, lower urine ammonium ion excretion, and lower fasting urine osmolality than those with a normal response. Considering both groups, the maximum urinary ammonium ion excretion was positively correlated with fasting urine osmolality (r2=0.34, P=0.002), suggesting that participants with sickle cell disease and lower urine concentration capacity have lower urine acidification capacity.ConclusionsAmong adults with sickle cell disease, impaired urinary acidification capacity attributable to distal tubular dysfunction is common and associated with the severity of hyposthenuria.PodcastThis article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_12_10_CJN07830719.mp3

UNDERSTANDING AGING IN TERMS OF PHYSIOLOGICAL STATES

The “network” of homeostatic systems fails in distinct ways in individual isogenic animals during the aging process. We believe that understanding these distinct physiological states, the transitions between them, and how they relate to homeostatic system functions will allow us to better affect change in the aging process. Work in yeast showed that fixing an initial system failure, loss of vacuole acidification capacity, could increase cellular lifespan. Here we showed how the long-lived physiological state conferred by high expression of the hsp-16.2 promoter based lifespan/penetrance biomarker correlates with differences in the expression of other genes, and the structure and function of lysosomes. We found that vacuole acidification failure is not a major initial proximal cause of aging in C. elegans – at least not in their intestine cells.

Chickpea production and soil chemical attributes after phosphorus and molybdenum fertilization

ABSTRACT Chickpea is the third most cultivated legume in the world. In Brazil, cropping of this legume is recent and definitions of fertilizer management techniques are scarce. In this study, the objective was to evaluate chickpea (BRS Aleppo) production and soil chemical attributes with and without phosphorus fertilization and leaf-applied molybdenum. A randomized block experimental design was used, with four replications. A 2 x 5 factorial arrangement was used to evaluate production, consisting of two molybdenum fertilization management practices (with and without molybdenum) and five application rates of P2O5 (0, 60, 120, 180, and 240 kg ha-1) in the form of single superphosphate. Soil sampling for evaluation of soil chemical attributes in the crop row and between rows was also considered. Molybdenum fertilization brought about greater stem and aboveground dry matter. Phosphorus fertilization increased stem, leaf, and seed yield, yielding a maximum of 2.83 t ha-1 seed at the rate of 200 kg ha-1 P2O5. However, maximum agronomic efficiency (8.30) was observed with the addition of 150 kg ha-1 P. Soil in the crop row attained higher concentrations of P, K, H+Al, and P-rem and reduction in pH, Ca concentration, SB, T, and V compared to between rows. Phosphorus rates reduced soil pH and increased T and the P concentrations, though only in the plant row. Between the rows, no changes were observed in soil chemical attributes, indicating low mobility of P and the acidification capacity of superphosphate in alkaline soils.

In vitro evaluation of the safety and probiotic and technological potential of Pediococcus pentosaceus isolated from sheep milk

Six isolates (Ac1Pd, Ac3Pd, Ac4Pd, Ac5Pd, Ac7Pd, and Ac22Pd) of Pediococcus pentosaceus from sheep milk were tested for safety and for probiotic and technological potential. The results showed that none of the isolates were able to produce biogenic amines or virulence factors. The isolates tested showed low hydrophobicities, high auto-aggregation capacities and co-aggregation with L. monocytogenes ATCC 7644, L. sakei ATCC 15521 and E. faecalis ATCC 19444, but none produced ?-galactosidase and bacteriocins. The isolates did not show growth at pH values 3 and 12, while in a pH range from 4 to 10 the growth was variable. In the absence of bile, all the isolates showed growth, with suppression at bile concentrations of 0.1%, 0.3%, 0.6% and 1.0%. In the disc-diffusion test, the isolates tested were resistant to oxacillin, sulfatrimethoprim and vancomycin but were sensitive to chloramphenicol and tetracycline. The isolates showed variable responses to penicillin G and were resistant to most of the drugs tested, except for amoxicillin trihydrate and ibuprofen. All cultures showed a high milk-acidification capacity after 24 hours and none produced exopolysaccharides. The isolates of P. pentosaceus were able to produce diacetyl; however, no culture showed extracellular proteolytic activity and the autolysis varied from 21.3% to 30.5% after 24 h. The isolates grew at NaCl concentrations of 4.0 and 6.0%, but the growth was lower at 10.0%. Finally, all the isolates were found to be safe but had limited application as probiotics and in some technological uses.