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.

Effect of biosynthetic intermediates and citrate on the phenyllactic and hydroxyphenyllactic acids production by Lactobacillus plantarum CRL 778.

AIM: To evaluate the influence of biosynthetic precursors, intermediates and electron acceptors on the production of antifungal compounds [phenyllactic acid (PLA) and hydroxyphenyllactic acid (OH-PLA)] by Lactobacillus plantarum CRL 778, a strain isolated from home-made sourdough. METHODS AND RESULTS: Growth of fermentative activity and antifungal compounds production by Lact. plantarum CRL 778 were evaluated in a chemically defined medium (CDM) supplemented with biosynthetic precursors [phenylalanine (Phe), tyrosine (Tyr)], intermediates [glutamate (Glu), alpha-ketoglutarate (α-KG)] and electron acceptors [citrate (Cit)]. Results showed that the highest PLA production (0.26 mmol l(-1)), the main antifungal compound produced by Lact. plantarum CRL 778, occurred when greater concentrations of Phe than Tyr were present. Both PLA and OH-PLA yields were increased 2-folds when Cit was combined with α-KG instead of Glu at similar Tyr/Phe molar ratio. Similarly, glutamate dehydrogenase (GDH) activity was significantly (P < 0.01) stimulated by α-KG and Cit in Glu-free medium. CONCLUSION: Phe was the major stimulant for PLA formation; however, Cit could increase both PLA and OH-PLA synthesis by Lact. plantarum CRL 778 probably due to an increase in oxidized NAD(+). This effect, as well as the GDH activity, was enhanced by α-KG and down regulated by Glu. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study where the role of Glu and GDH activity in the PLA and OH-PLA synthesis was evidenced in sourdough lactic acid bacteria (LAB) using a CDM. These results contribute to the knowledge on the antifungal compounds production by sourdough LAB with potential applications on the baked goods.

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.

Protease production by Leuconostoc oenos strains isolated from wine.

Two separate, extracellular proteolytic activities were demonstrated in four strains of Leuconostoc oenos isolated from Argentinian wines. The first took place in the early growth phase and the other had its maximum at the end of growth. The two proteolytic enzymes had different pH and temperature optima. Divalent metal ions had different effects not only on each L. oenos strain but also on each of the two proteases from each strain.