Malolactic bacteria from Trentino and their use in immobilized form

The immobilization of Oenococcus oeni strain PN4 with a new technology, and its use to perform malolactic fermentation (MLF) in wine is described. The immobilization was achieved with a two-steps process. Cells were entrapped in Ca-alginate microbeads, then coated with an organo-silica membrane obtained by two sol-gel treatments. The resulting material improves the physico-chemical features of alginate, avoids cell leakage during fermentation, and protects them from antimicrobial compounds. Experimental malolactic fermentations were carried out in microvinification scale; the activity of immobilized cells did not differ from that of free cells. The use of immobilized bacteria allowed some innovative approach at the MLF: i)the simultaneous alcoholic and malolactic fermentations in must by free yeast and immobilized bacteria; ii)the serial fermentation of subsequent wine lots with the same biomass of immobilized bacteria, for at least 45 days; iii)the achievement of MLF in a wine added with lysozyme, to suppress wild lactic bacteria and their potential spoilage.