Study On Malolactic Fermentation And Malolactic Enzyme Of Lactobacillus Plantarum

Lactic acid bacteria perform malolactic fermentation (MLF) after alcoholic fermentationin red wines. In this process, L-malic acid is converted into L-lactic acid, leading a decrease inwine acidity. Reduction of acid in red wine contributes taste, smell and stability to wine.Some Lactobacillus species have also displayed the MLF ability to survive the harsh wineconditions of which the species Lactobacillus plantarum has shown the most potential as astarter culture.The aim of the study was to evaluate Lactobacillus plantarum strains for use as possibleMLF starter cultures. This was done by assessing the viability, the L-malic acid degradationand total acidity of the most promising strains in sterile synthetic wine and wine afteralcoholic fermentation.Then6Lactobacillus. plantarum isolated for low pH, high ethanol andtotal SO2concentration to evaluate the tolerance of different factors. The effects of L-malicacid concentration, pH and temperature on malolactic enzyme of Lactobacillus plantarumCS-1were investigated and producing malolactic enzyme condition was optimized byresponse surface methodology.1.8Lactobacillus plantarum which inoculated in sterile synthetic wine showed the bestperformance and completed the fermentation in6days. Then4of the strains were inoculatedin wine to assess the ability of malolactic fermentation. The L-malic acid degradation was1.5g/L after inoculated15days. In conclusion, this study showed, L. plantarum CS-1, XJA-2,SC-20, SC-16have the potential to be utilised as MLF starter cultures.2. A factorial design was used to assess the effects of pH, SO2and ethanol concentrationand their interactions determined by the density difference of6Lactobacillus plantarum in aMRS medium. These results suggested that all strains tested could stand with pH3.0and75mg/L SO2, while5of them could stand with16%ethanol concentration. The effective orderof the three factors in orthogonal experiment was SO2concentration＞pH＞ethanolconcentration.3. A factorial design was used to assess the effects of L-malic acid concentration, pH and temperature on malolactic enzyme of Lactobacillus plantarum CS-1in a MRS medium. Theresults of response surface analysis suggested that the optimized producing malolacticenzyme conditions of Lactobacillus Plantarum CS-1were fermentation temperature30.93℃,pH value4.04, concentration of L-malic acid5.99g/L. Under the optimal conditions, MLEactivity was16.97U.