Yeast microbiota associated with spontaneous sourdough fermentations in the production of traditional wheat sourdough breads of the Abruzzo region (Italy).

The aims of this study were to describe the yeast community of 20 sourdoughs collected from central Italy and to characterize the sourdoughs based on chemical properties. A polyphasic approach consisting of traditional culture-based tests (spore-forming and physiological tests) and molecular techniques (PCR-RFLP, RAPD-PCR, PCR-DGGE) and chemical analysis (total acidity, acids, and sugar contents), was utilized to describe the yeast population and to investigate the chemical composition of the doughs. PCR-RFLP analysis identified 85% of the isolates as Saccharomyces cerevisiae, with the other dominant species being Candida milleri (11%), Candida krusei (2.5%), and Torulaspora delbrueckii (1%). RAPD-PCR analysis, performed with primers M13 and LA1, highlighted intraspecific polymorphism among the S. cerevisiae strains. The diversity of the sourdoughs from the Abruzzo region is reflected in the chemical composition, yeast species, and strain polymorphism. Our approach using a combination of phenotypic and genotypic methods identified the yeast species in the 20 sourdough samples and provided a complete overview of the yeast populations found in sourdoughs from the Abruzzo region.

Compositional and tissue modifications induced by the natural fermentation process in table olives.

Olive fruits contain high concentrations of phenols that include phenolic acids, phenolic alcohols, flavonoids, and secoiridoids. The final concentration of phenols is strongly affected by brine conditions. The factors involved in modification by brine are still partially unknown and can include hydrolysis of secoiridoid glucosides and the release of hydrolyzed products. In this study olives from various Italian cultivars were processed by natural fermentation (e.g., without a preliminary treatment of olives with NaOH) using a selected Lactobacillus strain. Processed olives are characterized by a low phenolic concentration of phenols, consisting mainly of phenyl alcohols, verbascoside, and the dialdehydic form of decarboxymethylelenolic acid linked to (3,4-dihydroxyphenyl)ethanol (3,4-DHPEA-EDA), whereas a high level of phenols occurs in olive brine from all the cultivars studied. Olives of the Coratina cultivar, control and with fermentation by Lactobacillus pentosus 1MO, were analyzed in a frozen hydrated state by cryo scanning electron microscopy and energy-dispersive X-ray microanalysis, on both surface and transversal freeze-fracture planes. Structural modifications, found in olives after fermentation, may explain the phenol release in brine.

Raw milk traditional Italian ewe cheeses as a source of Lactobacillus casei strains with acid-bile resistance and antigenotoxic properties.

Twenty-five Lactobacillus casei group strains isolated from ewe cheeses from Abruzzo region, central Italy, were identified by 16S rRNA gene sequencing, differentiated by RAPD-PCR analysis and characterized as in vitro for acid-bile tolerance and antigenotoxic properties. All the strains were very susceptible to simulated gastric fluid (pH 2.0) but most of them recovered viability (ca. 2-3 log-units) when transferred and maintained in simulated intestinal fluid (0.5% w/v bovine bile) for 3 h. Some strains showed potential for deactivating representative genotoxins as highlighted by the SOS-Chromotest. Twelve were active and nine moderately active against 4-nitroquinoline-1-oxide, and one active and only one moderately active against N-methyl-N'-nitro-N-nitrosoguanidine. The active strains produced evident spectroscopic modification of genotoxins after co-incubation. Most isolates with antigenotoxic activity resulted as acid-bile tolerant demonstrating that cheese autochthonous lactobacilli may reach the gut as a viable form and prevent genotoxin DNA damage.

The role of environmental factors and medium composition on bacteriocin-like inhibitory substances (BLIS) production by Enterococcus mundtii strains.

Bacteriocin-like inhibitory substances (BLIS)-producers Enterococcus mundtii WGWT1-1A, WGW11.2, WGJ20.1, WGJ40.2 and WGK53 from raw material origin were subjected to a study for the characterization of antimicrobial compound production under several growth conditions, including different cultivation media, growth temperatures, pHs, different concentrations and sources of nitrogen compounds, carbohydrates and other nutritional factors, and in the presence of different percentages of ethanol and NaCl. The five E. mundtii strains showed different behaviors. However, in all cases, MRS and sour dough bacteria (SDB) were found as the optimal media for BLIS production. In general, the higher BLIS production was observed with pH in the range 6.0-8.0 and, except 45 degrees C, the temperature did not show a defining effect. Low or no BLIS activity was detected after growth without nitrogen sources and carbohydrates. Absence of Tween 80, triammoniun citrate, K2HPO4, MgSO4 and MnSO4 did not affect BLIS activity levels. Except for a strain (WGWT1-1A), ethanol did not play a negative role in BLIS expression, while NaCl determined decrease of BLIS activity, proportional with concentration. The above strains did not contain plasmids, hence, BLIS expression is encoded by chromosomal DNA.

Identification of subdominant sourdough lactic acid bacteria and their evolution during laboratory-scale fermentations.

Presumptive lactic acid bacterial cocci were found in six sourdoughs (out of 20) from the Abruzzo region (central Italy) and subjected to phenotypic and genotypic characterization. A total of 21 isolates, recognized as seven strains by randomly amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR) typing, were identified by a polyphasic approach, consisting of 16S rRNA gene sequencing, multiplex PCR assays and physiological features, as Enterococcus faecium and Pediococcus pentosaceus. Four strains belonging to those species and previously isolated from wheat kernels were inoculated in sterile flour to verify their capacity to grow in sourdough environment. Doughs with several dual bacterial combinations, including Lactobacillus sanfranciscensis, were propagated for 11 days and pH measurements and bacterial counts were carried out.

Combination of multiplex PCR and PCR-denaturing gradient gel electrophoresis for monitoring common sourdough-associated Lactobacillus species.

A combination of denaturing gradient gel electrophoresis (DGGE) and a previously described multiplex PCR approach was employed to detect sourdough lactobacilli. Primers specific for certain groups of Lactobacillus spp. were used to amplify fragments, which were analyzed by DGGE. DGGE profiles obtained from Lactobacillus type strains acted as standards to analyze lactobacilli from four regional Abruzzo (central Italy) sourdoughs.