Objective: To achieve the high quality of malo-lactic starter cultures, we investigated the effect of three culture media on the direct inoculation viability, freeze-drying viability and membrane fatty acid composition of Oenococcus Oeni SD-2a.
Methods: We monitored the bacterial growth and change in medium pH when O. oeni SD-2a cells were cultured in ATB, FMATB and MATB media. O. oeni SD-2a cells in early stationary phase were harvested, and subjected to direct inoculation experiments and freeze-drying processes. Then we determined inoculation and freeze-drying viability. Membrane fatty acid composition of those corresponding O. oeni SD-2a cells was determined by GC/MS method.
Results: The results showed ATB medium without supplementation of DL-malate had weak pH buffering capability. Compared with FMATB and MATB, O. oeni cells cultured in ATB increased inoculation viability and freeze-drying viability. Concerning the membrane fatty acid composition, it was observed that ATB medium increased distinctly the relative concentration of lactobacillic acid (C19cyc11) and U/S (the unsaturated: saturated fatty acid) ratio in cell membrane lipid composition of O. oeni SD-2a.
Conclusion: The increased resistance to wine stressor and freeze-drying was probably a result of the cross protection conferred by self acid stress response induced in ATB medium, which might be related with changes in membrane fatty acid composition of O.oeniSD-2a. Therefore, ATB medium was more suitable for preparation of O. oeni SD-2a commercial starter cultures.