Seventeen heterofermentative lactobacilli isolated from kefir grains were characterized by molecular methods. Bacterial isolates were identified by amplification of 16S rRNA gene and analysis by Amplified Ribosomal DNA Restriction Analysis (ARDRA), using the restriction enzymes Hae III, Dde I, and Hinf I. ARDRA analysis of lactobacilli isolates showed, for each enzyme used, a same banding pattern between the heterofermentative lactobacilli and the reference strains Lactobacillus kefir JCM 5818 and Lb. kefir ATCC 8007. Other reference lactobacilli and one homofermentative isolate showed differences in at least one of these patterns. The 16S-23S rRNA spacer region was also used to discriminate the bacterial isolates at the species level. The data obtained from the analysis of spacer region confirmed that sequencing of this genome region is a good tool for a reliable identification of members of Lb. kefir species. Genotyping of isolates was performed by Random Amplified Polymorphic DNA (RAPD-PCR) analysis using M13, Coc, ERIC-2 and 1254 primers. Patterns obtained allowed the differentiation of isolates in three groups. The three clusters showed by RAPD-PCR analysis could be correlated with at least three different strains of Lb. kefir species in the group of heterofermentative lactobacilli isolates obtained from Argentinian kefir grains.

Lactiplantibacillus plantarum strain UNQLp 11 is a lactic acid bacterium with the potential to carry out malolactic fermentation (MLF) in red wines. Recently, the complete genome of UNQLp 11 was sequenced and this strain possesses four loci of the enzyme β-glucosidase. In order to demonstrate that these glucosidase enzymes could be functional under harsh wine conditions, we evaluated the hydrolysis of p-nitrophenyl-β-D-glucopyranoside (p-NPG) in synthetic wine with different ethanol contents (0%, 12%, and 14% v/v) and at different pH values (3.2, 3.5, and 3.8). Then, the hydrolysis of precursor n-octyl β-D-glucopyranoside was analyzed in sterile Pinot Noir wine (containing 14.5% v/v of ethanol, at different pH values) by headspace sorptive extraction gas chromatography-mass spectrometry (HSSE-GC/MS). The hydrolysis of p-NPG showed that β-glucosidase activity is very susceptible to low pH but induced in the presence of high ethanol content. Furthermore, UNQLp 11 was able to release the glycosilated precursor n-octyl, during MLF to a greater extent than a commercial enzyme. In conclusion, UNQLp 11 could improve the aromatic profile of the wine by the release of volatile precursors during MLF.

The rhizosphere-associated microbiome has diverse functions that support plant growth and health, varying among plant species, vegetation growth stages and environmental habitats. This microbiome includes a group of bacteria denominated plant growth-promoting rhizobacteria (PGPR) which can colonize plant roots. Certain PGPR isolates improve the ability of plants to adapt to a stressful environment. In this study, we collected and characterised the rhizosphere-associated bacteria, or epiphytic rhizobacteria, from Malbec and Cabernet-Sauvignon vineyards from the main wine-producing provinces of Argentina to analyse their potential use as biologic fertilisers and/or as pathogen-control agents. A total of 170 bacterial isolates were obtained, distributed into eleven different genera and classified into three phyla, Proteobacteria, Actinobacteria and Firmicutes. The in vitro analysis for plant-growth-promoting (PGP) activities demonstrated that a significant number of bacterial isolates had one or more of these traits. The Pseudomonas was the genus with the highest number of isolates and PGP activities, followed by the Arthrobacter, Serratia, Bacillus andPantoea. We observed that bacterial isolates identified as Bacillus exhibited a remarkable production of hydrolytic enzymes related to biocontrol activities. Biocontrol trials from the Bacillus collection revealed that at least five isolates were able to inhibit the fungal growth of Botrytis cinerea and Alternaria alternata. The results obtained suggest the biological potential of each isolate and the relevance of proceeding to greenhouse and field assays to obtain long-term environmentally compatible bio-products for vineyard management.