Isolamento, identificazione e caratterizzazione tecnologica di Lactobacillus plantarum da vini rossi tradizionali dell'Italia meridionale

Aims: Malolactic fermentation (MLF) plays an important role in the production of wine, especially red wines, resulting in microbial stability, deacidification, as well as contributing to the aroma profile. Nowadays, the use of lactic acid bacteria (LAB) strains as malolactic starter cultures to improve the wine quality is a common winemaking practice. However, the induction of malolactic fermentation by use of commercially available strains is not always successful. Several reports have shown that the success of MLF starters depends on strain and is influenced by several factors, including geographical origin and adaptation to the winemaking conditions of each wine. Recently some authors have evidenced that L. plantarum specie shows a more different enzymatic profile than others LAB species, which could play an important role in the modification of the wine aroma profile. Therefore, this work, was focused to the isolation, identification and technological characterization of L. plantarum from traditional red southern Italian wines that can be used in the biological deacidification of wines. Methods and Results: L. plantarum strains were isolated from twenty-three type of red wines undergoing spontaneous MLF. Samples were taken at the end of alcoholic fermentation and during MLF. Wine samples were diluted in a sterile physiological solution and plated on MRS agar. Identification of L. plantarum strains was performed before through phenotypic characterization and after by PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) using specific primers, 16S rRNA gene sequencing and by MALDI TOF/TOF. Strains were further biotyped using RAPD-PCR (randomly amplified polymorphic DNA-polymerase chain reaction) analysis. Then, 58 strains were inoculated in a synthetic wine like media to evaluate their capacity to grow and to perform MLF. A positive correlation between the malolactic activity performance and the ability to develop and tolerate stress conditions was observed for eleven selected L. plantarum strains. Special attention was given to phenolic compounds infact the potentially effect of a phenol compound (malvin-3,5-diglucoside) on the growth of L. plantarum strains was investigated. Other important technological properties that were considered for this study were the assessment of the ability of the strains to produce bacteriocins, assessment to produce biogenic amines; this is very important because their presence in wine is considered as marker molecules of quality loss and . may have toxic effects on human health. The final step of this work has been to evaluate as the eleven L. plantarum strains can affect the organoleptic properties of wines, infact LAB can produce enzymes that can transform neutral grape compounds into flavour-active compounds, for this reason was investigated their ability to hydrolyze glucosidic aroma precursors. Significance and Impact of the Study: The results reported are useful for the selection of indigenous MLF starter cultures with desired oenological traits from typical regional wines. It should be the base for the improvement in organoleptic quality of typical red wine.