| DAR/BDH | Microorganisms | |
| LD | cpLN | |
| Genes localizationand transcription type | Chromosomic genes, enhanced under acidic conditions (pH 5) and partially repressed by the presence of citrate [1] [24] [25] [30] . | Plasmidic genes for Ln pseudomesenteroides [60] Ln lactis: low constitutive transcription partially repressed by citrate addition [28] . |
| Activating factors/ optimal activity parameters | Optimum pH for the reduction of diacetyl: between 5.8 and 6.1Optimum pH for the oxidation of 2,3-butanediol: between 8.5 and 10 [54] . | Optimal pH for Ln lactis: 5.7 [28] Optimal pH for Ln pseudomesenteroides: 5.5 for the reductive activity and 7.5 for the oxidative activityOptimal temperature for Ln pseudomesenteroides: 40˚C, and active from 20˚C to 55˚C [55] . |
| Inhibitory factors | pH of 4.5 [54] . | - |
| Enzymes characteristicsa | The diacetyl reductase activity is 7- and 4.7-fold higher (for the two DAR) than the acetoin reductase activity with 10 mM of substrate. When the two substrates are present, acetoin is the preferred substrate for the two DAR [54] . Km for diacetyl: 9 mMKm for acetoin: 0,2 mMAcetoin acts as inhibitor at concentrations above 1 mM [3] , Coenzyme: specific for NADH [28] . | Km for diacetyl, acetoin and meso-2,3-butanediol for Ln pseudomesenteroides: 5.1, 0.34 and 1.67 mM at pH 5.5, 5.5 and 7.5; respectively [55] . Coenzyme: Ln lactis: specific for NADPH [28] Ln pseudomesenteroides: diacetyl reductase requires only NADH as coenzyme for the diacetyl reduction and either NADH or NADPH for the acetoin reduction. The enzyme catalyzes the oxidation of meso-2,3-butanediol only with the NAD+ [55] . |