mlO Medium

Malolactic fermentation is a biochemical process, conducted in most red wines and some white wines by certain lactic acid bacteria, which results in a lower titratable acidity, improved microbial stability, and improved flavor and mouthfeel. Oenococcus oeni is the major bacterial species found in wines during the malolactic fermentation and is well adapted to the low pH and high ethanol concentration of wine.

Tryptone and yeast extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Glucose and fructose are used as the carbon and energy sources. The use of fructose in the growth medium as an electron acceptor has usually been seen as beneficial for most strains of O. oeni. Magnesium sulphate and manganese sulphate provide inorganic ions. Citrate is an alternative energy source to sugar metabolism, is related with the diacetyl production in wines and, at a low pH, inhibits most microorganisms. L-Cysteine hydrochloride is the reducing agent. Tween 80 is an emulsifier.

Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.

Preparation

Dissolve 35.2 grams of dehydrated medium in 900 mL of distilled water. Mix well and dissolve by heating to complete dissolution. Dispense into appropriate containers and sterilize at 121 °C for 10 minutes. Cool to 50 °C and add 100 mL of sterile Tomato Serum.

The microbiological test should be carried out by the end-user laboratory.

• Caspritz, G. and Radler, F. (1983). Malolactic Enzyme of Lactobacillus plantarum. Purification, properties, and distribution among bacteria. The Journal of Biological Chemistry, 258 (8), 4907-4910.
• Callejón, S., Polo, L., Ferrer, S. and Pardo, I. (2007). Seguimiento mediante FISH de bacterias lácticas durante la vinificación. In M. Ramírez Fernández, Avances en ciencias y técnicas enológicas (pp. 136 y 137). Badajoz.
• Maicas, S., González-Cabo, P., Ferrer, S. and Pardo, I. (1999). Production of Oenococcus oeni biomass to induce malolactic fermentation in wine by control of pH and substrate addition. Biotechnology Letters, 21, 349-353.
• Margalef-Català, M., Araque, I., Bordons, A., Reguant, C. and Bautista-Gallego, J. (2016). Transcriptomic and Proteomic Analysis of Oenococcus oeni Adaptation to Wine Stress Conditions. Frontiers in Microbiology, 7,1-18.