Effect of culture parameters on the heat tolerance and inorganic polyphosphate accumulation by Lacticaseibacillus rhamnosus CRL1505, a multifunctional bacterium.

Lacticaseibacillus rhamnosus CRL1505 can be used in functional products as a probiotic powder (dried live cells) or as a postbiotic intracellular extract containing inorganic polyphosphate as a functional biopolymer. Thus, the aim of this work was to optimize the production of Lr-CRL1505 depending on the target of the functional product (probiotic or postbiotic). For this purpose, the effect of culture parameters (pH, growth phase) on cell viability, heat tolerance and polyphosphate accumulation by Lacticaseibacillus rhamnosus CRL1505 was evaluated. Fermentations at free pH produced less biomass (0.6 log units) than at controlled pH while the growth phase affected both polyphosphate accumulation and cell heat tolerance. Exponential phase cultures showed 4-15 times greater survival rate against heat shock and 49-62% increased polyphosphate level, compared with the stationary phase. Results obtained allowed setting the appropriate culture conditions for the production of this strain according to its potential application, i.e., as live probiotic cells in powder form or postbiotic. In the first case, running fermentations at pH 5.5 and harvesting the cells at the exponential phase are the best conditions for obtaining a high live biomass yield capable of overcoming heat stress. Whereas the postbiotic formulations production requires fermentations at free pH and harvesting the cells in exponential phase to increase the intracellular polyphosphate level as a first step.

Consortia of lactic acid bacteria strains increase the antioxidant activity and bioactive compounds of quinoa sourdough - based biscuits.

The aim of this work was to use consortia (two or three strains) of lactic acid bacteria (LAB) [Lactiplantibacillus plantarum CRL 1964 and CRL 1973, and Leuconostoc mesenteroides subsp. mesenteroides CRL 2131] to obtain quinoa sourdoughs (QS) for further manufacturing of quinoa sourdough-based biscuits (QB). Microbial grow and acidification were evaluated in QS while antioxidant activity (AOA), total phenolic compounds (TPC) and total flavonoid compounds (TFC) were determined in QS and QB. QS inoculated with LAB consortia respect to monocultures showed higher growth and acidification, AOA (7.9?42.6%), TPC (19.9?35.0%) and TFC (6.1?31.6%). QB prepared with QS inoculated by LAB consortia showed higher AOA (5.0-81.1%), TPC (22.5?57.5%) and TFC (14.0-79.9%) than biscuits inoculated by monocultures sourdoughs. These results were attributed to a synergic effect from LAB consortia. Principal component analysis showed the highest scores of the evaluated characteristics for biscuits made with consortia sourdough of two (CRL1964?+?CRL2131) and three (CRL1964?+?CRL1973?+?CRL2131) strains.

Development of an ophthalmic formulation with a postbiotic of Lactiplantibacillus plantarum CRL 759.

The term postbiotics has acquired great interest in recent years. Numerous studies have shown a potential beneficial effect of its use in many inflammatory pathologies. However, it has not been much explored in ocular inflammatory diseases. The aims of this study were to develop and characterise an ophthalmic formulation with a postbiotic of Lactiplantibacillus plantarum CRL 759, and to evaluate its anti-inflammatory actions on murine macrophage stimulated with lipopolysaccharides (LPS) in vitro. First, we evaluated the ability of L. plantarum CRL 759 to generate a supernatant with anti-inflammatory property using different buffers. Then, we studied the stability at different temperatures and storage times of the generated postbiotic. In vitro assays showed that incubation of L. plantarum CRL 759 in modified phosphate buffer according to Sorensen (called POF-759), generated a supernatant that significantly reduced the production of interleukin-6, tumour necrosis factor-α, and nitric oxide by RAW 264.7 cells stimulated with LPS. Furthermore, POF-759 maintained its anti-inflammatory activity at room temperature, 4 and -20 °C, up to 30 days of storage. From the studies reported here, a postbiotic product with anti-inflammatory properties and optimal characteristics for the formulation of eye drops was obtained.

Inorganic Additive Improves the Survival of the Probiotic Lacticaseibacillus rhamnosus CRL1505 During Spray Drying, Rehydration, and Storage.

In previous in vitro studies, an inorganic additive (MCM3) showed a thermo-protective effect on the cell viability of Lacticaseibacillus rhamnosus CRL1505 (Lr-CRL1505). In this work, cultures of this probiotic strain were spray dried at lab scale using two carriers: maltodextrin (powder MA) and maltodextrin plus MCM3 (powder MA/MCM3). The cell survival was higher in powder MA/MCM3 (72.8%) than in powder MA (42.8%). Different rehydration media, including the additive MCM3, and two temperatures (37 °C and 45 °C) were evaluated. The best results were obtained in cells rehydrated at 37 °C in MCM3. During the storage of the powders, the highest cell counts were observed in the MA/MCM3 powder. Our results demonstrated that the presence of MCM3 in the carrier and in reconstitution media benefits the spray drying process and the recovery of dehydrated cells. Thus, the use of this additive of inorganic nature and low cost represents a promising technological alternative.

Whey protein coating bead improves the survival of the probiotic Lactobacillus rhamnosus CRL 1505 to low pH.

AIMS: To evaluate the efficacy of a novel microencapsulation procedure using whey protein and pectin to improve the survival rate of Lactobacillus rhamnosus CRL 1505 to low pH and bile. METHODS AND RESULTS: Lactobacillus rhamnosus CRL 1505 was encapsulated by ionotropic gelation using pectin (PE) and pectin-whey protein (PE-WP). Both types of beads (MC(PE/WP) and MC(PE-WP/WP)) were covered with a layer of whey protein by complex coacervation. The noncapsulated lactobacilli were not sensitive to bile salts but to acid. Both microparticles protected Lact. rhamnosus CRL 1505 at pH 2.0, but only MC(PE/WP) was effective at pH 1.2. CONCLUSIONS: The combination of ionotropic gelation and complex coacervation techniques is efficient to obtain microcapsules of pectin covered with whey proteins. The MC(PE/WP) beads were more stable than the MC(PE-WP/WP) beads in simulated gastric conditions, thus offering better protection to Lact. rhamnosus CRL 1505 at low pH. SIGNIFICANCE AND IMPACT OF THE STUDY: Pectin beads with a whey protein layer (MC(PE/WP)) could be used as probiotic carrier in functional foods of low pH (e.g. apple juice), thus protecting Lact. rhamnosus CRL 1505 against the stressful conditions of the gastric tract.

Inhibition of citrus fungal pathogens by using lactic acid bacteria.

The effect of lactic acid bacteria (LAB) on pathogenic fungi was evaluated and the metabolites involved in the antifungal effect were characterized. Penicillium digitatum (INTA 1 to INTA 7) and Geotrichum citri-aurantii (INTA 8) isolated from decayed lemon from commercial packinghouses were treated with imazalil and guazatine to obtain strains resistant to these fungicides. The most resistant strains (4 fungal strains) were selected for evaluating the antifungal activity of 33 LAB strains, among which only 8 strains gave positive results. The antifungal activity of these LAB strains was related to the production of lactic acid, acetic acid, and phenyllactic acid (PLA). A central composite design and the response surface methodology were used to evaluate the inhibitory effect of the organic acids produced by the LAB cultures. The antifungal activity of lactic acid was directly related to its concentration; however, acetic acid and PLA showed a peak of activity at 52.5 and 0.8 mM, respectively, with inhibition rates similar to those obtained with Serenade((R)) (3.0 ppm) imazalil (50 ppm) and guazatine (50 ppm). Beyond the peak of activity, a reduction in effectiveness of both acetic acid and PLA was observed. Comparing the inhibition rate of the organic acids, PLA was about 66- and 600-fold more effective than acetic acid and lactic acid, respectively. This study presents evidences on the antifungal effect of selected LAB strains and their end products. Studies are currently being undertaken to evaluate the effectiveness in preventing postharvest diseases on citrus fruits.

A ready-to-use antifungal starter culture improves the shelf life of packaged bread.

Fungal spoilage is the main cause of economic loss in the baking industry. In this study, we developed a ready-to-use biopreserver (slurry [SL]) for nonsliced packed bread by using selected antifungal lactic acid bacteria (LAB) and low-cost ingredients that are compatible with the food matrix. Four LAB strains (Lactobacillus brevis CRL 772, L. brevis CRL 796, L. plantarum CRL 778, and L. reuteri CRL 1100) tested in bread preservation were able to inhibit Penicillium sp. growth and lengthen shelf life twofold with respect to breads prepared using only Saccharomyces cerevisiae (2 days shelf life). The best biopreservation effect (5 days shelf life) was obtained with 40% antifungal slurry SL778 containing L. plantarum CRL 778; this was as effective as 0.2% calcium propionate (PCa). The antifungal effect of SL778 was related to the synthesis of acetic and phenyllactic acid as well as lactic acid, which was produced at a high concentration (31.2 mmol/kg) and lowered the pH of the dough, favoring the undissociated fraction of the organic acids. The combination of the starter SL778 with 0.4% PCa extended the shelf life of packaged bread to 24 days, 2.6-fold longer than breads prepared with only 0.4% PCa.

Lactobacillus reuteri CRL 1100 as starter culture for wheat dough fermentation.

The effect of sucrose on the fermentation balance of Lactobacillus reuteri CRL 1100 and the invertase activity of this strain in wheat dough and culture medium (MRSs) was evaluated. The enzyme activity was dependent on the environmental pH releasing glucose and fructose from sucrose hydrolysis. Glucose was used as carbon source, while fructose was mainly used as electron acceptor to produce mannitol up to 10h of fermentation. Thereafter, fructose seemed to be metabolized by the heterofermentative pathway, which determined an increase in the concentration of acetate (6 mmol l(-1)), lactate (2 mmol l(-1)) and ethanol (1 mmol l(-1)) and the lack of mannitol formation after glucose depletion. The fermentation balance of Lb. reuteri CRL 1100 during the dough fermentation resulted in lower (63%) ethanol, higher (75%) acetate production and soluble carbohydrates concentrations, like MRSs cultures. This fermentation profile would be important to obtain an optimal growth of yeast and the optimal bread flavor and taste.

Functionality of lactic acid bacteria peptidase activities in the hydrolysis of gliadin-like fragments.

AIMS: To evaluate the role of the peptidase activities from sourdough lactic acid bacteria (LAB) in the degradation of alpha-gliadin fragments. METHODS AND RESULTS: Different proline-containing substrates were hydrolysed by LAB indicating pro-specific peptidase activities. Lactobacillus plantarum CRL 775 and Pediococcus pentosaceus CRL 792 displayed the highest tri- and di-peptidase activities, respectively. Lactobacillus plantarum strains hydrolysed more than 60%alpha-gliadin fragments corresponding to the 31-43 and 62-75 amino acids in the protein after 2 h. None of the LAB strains alone could hydrolyse 57-89 alpha-gliadin peptide; however, the combination of L. plantarum CRL 775 and P. pentosaceus CRL 792 led to hydrolysis (57%) of this peptide in 8 h. CONCLUSIONS: The capacity of LAB strains to degrade alpha-gliadin fragments was not correlated to individual peptidase activities. Several strains separately degraded the 31-43 and 62-75 alpha-gliadin fragments, while the 57-89 peptide degradation was associated with the combination of peptidase profiles from pooled LAB strains. This is the first report on the peptide hydrolase system of sourdough pediococci and its ability to reduce alpha-gliadin fragments. SIGNIFICANCE AND IMPACT OF THE STUDY: This study contributes to a better knowledge of sourdough LAB proteolytic system and its role in the degradation of proline-rich alpha-gliadin peptides involved in celiac disease.

Gluten breakdown by lactobacilli and pediococci strains isolated from sourdough.

AIMS: To evaluate the growth and metabolic activity of lactobacilli and pediococci strains in a gluten base medium (GBM), formulated for a proper selection of proteolytic strains to be used in sourdough fermentation. METHODS AND RESULTS: Proteolytic activity by lactic acid bacteria (LAB) was evaluated by SDS-PAGE and by the amino acids released determined by reversed-phase high-performance liquid chromatography. Only 13 LAB (nine lactobacilli and four pediococci), among the 42 evaluated were able to utilize gluten as nitrogen source and to grow in GBM. Pediococcus pentosaceus CRL 797 showed a similar proteolytic activity to lactobacilli strains. In the majority of the cultures, basic amino acid group increased (c. 80% after 12 h incubation) mainly due to the release of ornithine, a flavour precursor of bread. Lysine, a limiting essential amino acid in wheat flour, increased by 150% in cultures of P. pentosaceus CRL 797. CONCLUSIONS: This study allows selecting P. pentosaceus CRL 797 and L. plantarum CRL 759 as potential starter culture for type III sourdough fermentation. It is shown for the first time that pediococci strains isolated from sourdough are proteolytically active on gluten. SIGNIFICANCE AND IMPACT OF THE STUDY: The physiological studies on gluten breakdown by LAB will contribute to the better selection of strains to produce breads with enhanced organoleptic characteristics.