Control of Zymoseptoria tritici cause of septoria tritici blotch of wheat using antifungal Lactobacillus strains.

AIMS: This study explored an effective biological control agent based on lactic acid bacteria culture or culture supernatant, which was effective against fungicide-resistant Zymoseptoria tritici, which causes septoria tritici blotch (STB). METHODS AND RESULTS: Three lactic acid bacteria strains which exhibited broad antifungal activity were investigated for their potential to control Z. tritici. Plate assays, liquid culture growth inhibition assays and STB biocontrol seedling tests were employed. Lactobacillus brevis JJ2P and Lactobacillus reuteri R2 caused significant fungal inhibition as observed by large mycelium clearing on modified MRS agar. Cell-free culture supernatants of Lact. brevis JJ2P and Lact. reuteri R2 showed antifungal activity against Z. tritici, as observed by mycelial radial growth inhibition and liquid culture growth inhibition. Cell-free supernatants of these anti-Z. tritici LAB strains were assessed in vivo for their abilities to inhibit STB development in seedling tests. Lact. brevis JJ2P was capable of inhibiting disease development and significantly reduced the diseased leaf area covered with pycnidia. CONCLUSIONS: Biological control accomplished by beneficial micro-organisms such as Lact. brevis JJ2P may represent an alternative control strategy for reducing STB. SIGNIFICANCE AND IMPACT OF THE STUDY: Globally, STB is regarded as one of the most important diseases of wheat. Control of Z. tritici is heavily reliant on fungicide application. The recent emergence of resistance or reduced sensitivity to fungicides among Z. tritici populations has urgently called for the development of new control strategies.

Evaluation of exopolysaccharide producing Weissella cibaria MG1 strain for the production of sourdough from various flours.

This study determined exopolysaccharide (EPS) production by Weissella cibaria MG1 in sourdoughs prepared from gluten-free flours (buckwheat, oat, quinoa and teff), as well as wheat flour. Sourdoughs (SD) were fermented without sucrose, or by replacing 10% flour with sucrose to support EPS production. The amount of EPS depended on the substrate: high amounts of EPS corresponding to low amounts of oligosaccharides were found in buckwheat (4.2 g EPS/kg SD) and quinoa sourdoughs (3.2 g EPS/kg SD); in contrast, no EPS but panose-series oligosaccharides (PSO) were detected in wheat sourdoughs. Organic acid production, carbohydrates and rheological changes during fermentation were compared to the EPS negative control without added sucrose. Corresponding to the higher mineral content of the flours, sourdoughs from quinoa, teff and buckwheat had higher buffering capacity than wheat. Fermentable carbohydrates in buckwheat, teff and quinoa flours promoted W. cibaria growth; indicating why W. cibaria failed to grow in oat sourdoughs. Endogenous proteolytic activity was highest in quinoa flour; α-amylase activity was highest in wheat and teff flours. Protein degradation during fermentation was most extensive in quinoa and teff SD reducing protein peaks 18-29, 30-41 and 43-55 kDa extensively. Rheological analyses revealed decreased dough strength (AF) after fermentation, especially in sucrose-supplemented buckwheat sourdoughs correlating with amounts of EPS. High EPS production correlated with high protein, fermentable sugars (glucose, maltose, fructose), and mineral contents in quinoa flour. In conclusion, W. cibaria MG1 is a suitable starter culture for sourdough fermentation of buckwheat, quinoa and teff flour.

Barley malt wort fermentation by exopolysaccharide-forming Weissella cibaria MG1 for the production of a novel beverage.

AIMS: The growing interest of governments and industry in developing healthy and natural alternative foods and beverages that will fulfil the consumer drive towards a healthy lifestyle and clean-label, natural diet has led to an increase in traditional lactic acid bacteria fermentation research. In particular, this research aims to address the organoleptic modulation of beverages using in situ-produced bacterial polysaccharides. METHODS AND RESULTS: Weissella cibaria MG1 is capable of producing exopolysaccharides (dextran) and oligosaccharides (glucooligosaccharides) during sucrose-supplemented barley-malt-derived wort fermentation. Up to 36·4 g l(-1) of dextran was produced in an optimized system, which improved the rheological profile of the resulting fermentate. Additionally, small amounts of organic acids were formed, and ethanol remained below 0·5% (v/v), the threshold volume for a potential health claim designation. CONCLUSIONS: The results suggest that the cereal fermentate produced by W. cibaria MG1 could be potentially used for the production of a range of novel, nutritious and functional beverages. SIGNIFICANCE AND IMPACT OF THE STUDY: Using conventional raw materials and traditional processes, novel LAB-fermented beverages can be produced representing an innovative mechanism towards fulfilling the aim to decrease government and personal costs as well as potentially ameliorating consumer lifestyle regarding dietary-related disease.

Phenotypic, genotypic and technological characterization of predominant lactic acid bacteria in Pecorino cheese from central Italy.

AIMS: Identification and biotyping of lactic acid bacteria (LAB) isolated from raw-milk Pecorino cheese manufactured in the Marche region (central Italy) for selection of suitable starter cultures or adjuncts. METHODS AND RESULTS: Preliminary characterization with morphological and biochemical assays were undertaken for 112 Gram-positive and catalase-negative isolates. Unequivocal identification of the isolates was obtained through restriction analysis of the amplified 16S rRNA gene and sequencing of 360-380 bp amplicons. Fifty-nine isolates belonging to LAB species generally recognized as safe and potentially utilized as starters or flavour-producing adjuncts were preselected and tested for their acidifying, proteolitic and autolytic activities. Fifty-five of these isolates were also subject to RAPD (randomly amplified polymorphic DNA) fingerprinting and unweighted pair-group method with arithmetic averages (UPGMA) cluster analysis for the estimation of genotypic intra-species variation. As a result, in Pecorino cheese, a heterogeneous lactic acid bacteria population, which includes strains with metabolic characteristics of technological interest, was characterized. CONCLUSIONS: The polyphasic approach proposed allows the bacterial ecology of Pecorino cheese to be investigated and allows to assess the potential role of autochthonous LAB strains for the dairy industry. SIGNIFICANCE AND IMPACT OF THE STUDY: The great economic importance of Pecorino cheese encouraged a deeper knowledge of its microbiota, which is known to influence the peculiar sensory properties of this cheese, also in view of its exploitation.

Resident lactic acid bacteria in raw milk Canestrato Pugliese cheese.

AIMS: Investigation of the autochthonous lactic acid bacteria (LAB) population of the raw milk protected designation of origin Canestrato Pugliese cheese using phenotypic and genotypic methodologies. METHODS AND RESULTS: Thirty phenotypic assays and three molecular techniques (restriction fragment length polymorphism, partial sequencing of the 16S rRNA gene and recA multiplex PCR assay) were applied to the identification of 304 isolates from raw milk Canestrato Pugliese cheese. As a result, 168 of 207 isolates identified were ascribed to genus Enterococcus, 25 to Lactobacillus, 13 to Lactococcus and one to Leuconostoc. More in details among the lactobacilli, the species Lactobacillus brevis and Lactobacillus plantarum were predominant, including 13 and 10 isolates respectively, whereas among the lactococci, Lactococcus lactis subsp.cremoris [corrected] was the species more frequently detected (seven isolates). CONCLUSIONS: Except for the enterococci, phenotypic tests were not reliable enough for the identification of the isolates, if not combined to the genotype-based molecular techniques. The polyphasic approach utilized allowed 10 different LAB species to be detected; thus suggesting the appreciable LAB diversity of the autochthonous microbial population of the Canestrato Pugliese cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: A comprehensive study of the resident raw milk Canestrato Pugliese cheese microbial population has been undertaken.