Malolactic activity from Leuconostoc oenos ML34 is tightly associated with lactic dehydrogenase. A simple and fast procedure, involving affinity chromatography on agarose-hexane-NAD (Agnad), was used to separate malolactic activity from lactic dehydrogenase and other proteins. The yield was ca. 86%, the purification was 5.2-fold, and the Km values for L-malate, NAD+ and Mn2+ were 2.8, 0.13, and 0.028 mM, respectively, at a pH optimum of 5.8.

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SummaryWe report the isolation and immobilization of a nisinogenic strain (NZ1) ofLactococcus lactissubsp.lactis, active on gas-forming lactate-fermenting clostridia responsible for late blowing of Asiago and Montasio cheeses. The bacteriocin (nisin) produced by strain NZ1 is pronase-sensitive and is released in culture media during the growth phase. Using the sensitive indicator strainLactobacillus delbrueckiisubsp.bulgaricusNCDO 1489, a rapid microtitre plate based assay was developed for quantitative determination of the bacteriocin produced by NZ1 cells, either free or immobilized in gel beads. Scanning electron microscopy of cells immobilized in calcium alginate coated beads and viable counts of the surrounding medium showed that no cell leakage occurred during a 24 h assay. The bacteriocin released from immobilized cells reached, after 5 and 24 h, concentrations comparable to that of the free cell system after 3–4 h incubation in culture media.

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