Production of diacetyl and acetoin by lactic acid bacteria

Abstract

AbstractThe production of “butter aroma” compounds (diacetyl ‐ DC; acetoin ‐ AMC) by Leuconostoc sp. and Streptococcus diacetylactis was optimized in different cultural conditions. In batch cultures the productivity depended upon the medium, physiological state of strain and of temperature and time of cultivation. In milk media the production of DC did not exceed 4 mg/1 and of AMC 500 mg/1. The maximal level correlated to the early stationary growth phase of the producers. In lactose peptone medium with 1 % of sodium citrate, production of these compounds was about three times higher in comparison to media without citrate. In continuous culture DC and AMC production was high influenced by dilution rate (D). At D = 0.2 h−1 DC and AMC production was maximal, higher than in batch conditions. At D = 0.7 h−1 i.e. in the conditions of maximal productivity of biomass, DC production decreased to 60%‐80%.The improvement of aroma productivity of strains was obtained after mutation. Applying nitrosoquanidine and UV‐rays, standard mutagenic conditions and screening methods enabling to isolate active mutants we have obtained stable strains with 2‐6times higher DC and at about 50% improved AMC level. The stability of the mutants was very high for S. diacetylactis not only during their 2 years storage in liophylized state but also in standard laboratory culture conditions.