Malolactic fermentation Oenococcus oeni

Malolactic fermentation (MLF) is an important secondary fermentation that occurs in many wines generally about 2-3 weeks after completion of the alcoholic fermentation. Lactic acid bacteria, principally Oenococcus oeni (formerly Leuconostoc oenos) are responsible for this fermentation. 

Vidal, M. T., Poblet, M., Constanti, M., and Bordons, A. (2001). Inhibitory effect of copper and dichlofluanid on Oenococcus oeni and malolactic fermentation. Am.. Enol. Vitic. 52, 223-229. 

M. Esti, G. Volpe, L. Micheli, E. Delibato, D. Compagnone, D. Moscone and G. Palleschi, Electrochemical biosensors for monitoring malolactic fermentation in red wine using two strains of Oenococcus oeni, Anal. Chim. Acta, 513(1) (2004) 357-364. 

Usually, after alcoholic fermentation, the wine undergoes malolactic fermentation, induced primarily by Oenococcus oeni. Not only can this lactic acid bacterium convert L-malic acid into L-lactic acid but also it is involved in many other transformations fundamental to Amarone quality. 

Malolactic fermentation (MLF) in wine is by definition the enzymatic conversion of L-malic acid to L-lactic acid, a secondary process which usually follows primary (alcoholic) fermentation of wine but may also occur concurrently. This reduction of malic acid to lactic acid is not a true fermentation, but rather an enzymatic reaction performed by lactic acid bacteria (LAB) after their exponential growth phase. MLF is mainly performed by Oenococcus oeni, a species that can withstand the low pFi (<3.5), high ethanol (>10 vol.%) and high SO2 levels (50 mg/L) found in wine. More resistant strains of Lactobacillus, Leuconostoc and Pediococcus can also grow in wine and contribute to MLF especially if the wine pH exceeds 3.5 (Davis et al. 1986 Wibowo et al. 1985). The most important benefits of MLF are the deacidification of high acid wines mainly produced in cool climates, LAB contribute to wine flavour and aroma complexify and improve microbial sfabilify (Lonvaud-Funel 1999 Moreno-Arribas and Polo 2005). 

DTncecco, N., Bartowsky, E,L, Kassara, S., Lante, A., SpettoU, P. Henschke, P.A. (2004). Release of glycosidically bound flavour compounds of Chardonnay by Oenococcus oeni during malolactic fermentation. Pood Microbiol, 21, 257-265. 

Hernandez, T., Estrella, I., Perez-Gordo, M., Alegria, E-G., Tenorio, C., Ruiz-Larrea, R, Moreno-Arribas, M.V. (2007). Contribution of Oenococcus oeni and Lactobacillus plantarum to the non anthocyanin phenolic composicion of red wine during malolactic fermentation. J. Agric. Food Chem., 55, 5260-5266. 

Ugliano, M., Moio, L. (2006). The influence of malolactic fermentation and Oenococcus oeni strain on glycosidic aroma precursors and related volatile compounds of red wine. J. Sci. Food Agric., 86, 2468-2476. 

Ugliano M., Genovese, A., Moio, L. (2003). Hydrolysis of wine aroma precursors during malolactic fermentation with four commercial starter cultures of Oenococcus oeni. J. Agric. Food Chem., 51, 5073-5078. 

On the other hand, other studies focused on O. oeni amino acid requirements for growth and malolactic fermentation in several growth media (Tracey and Britz 1989). Remize et al. (2006) determined the essential amino acids for the growth of five different strains of Oenococcus oeni. These amino acids corresponded to glutamic acid, methionine, phenylalanine, serine and tyrosine for all the strains studied. They also found that the amino acids valine, leucine, tryptophan, isoleucine, histidine and arginine were essential or necessary for the strains studied, but that the amino acids alanine, glycine and proline were not essential. 

Boido, E., Lloret, A., Medina, K., Carrau, E., DeUacassa, E. (2002). Effect of ss-gfycosidase activity of Oenococcus oeni on the glycosylated flavor precursors of Tannat wine during malolactic fermentation J. Agric. Food Chem., 50, 2344—2349. 

Bartowsky, E.J. and Henschke, P.A. 1999. Use of polymerase chain reaction for specific detection of the malolactic fermentation bacterium Oenococcus oeni (formerly Leuconostoc oenos) in grape juice and wine samples. Aust. J. Grape Wine Res. 5, 39—44. 

Larsen, J.T., Nielsen, J.C., Kramp, B., Richelieu, M., Riisager, M.J., Ameborg, N., and Edwards, C.G. 2003. Impact of different strains of Saccharomyces cerevisiae on malolactic fermentation by Oenococcus oeni. Am. J. Enol. Vitic. 54, 246-251. 

Nielsen, J.C. and Richelieu, M. 1999. Control of flavor development in wine during and after malolactic fermentation by Oenococcus oeni. Appl. Environ. Microbiol. 65, 740-745. 

Reguant, C. and Bordons, A. 2003. Typification of Oenococcus oeni by multiplex RAPD-PCR and study of population dynamics during malolactic fermentation. J. Appl. Microbiol. 95, 344-353. 

Semon, MJ., Edwards, C.G., Forsyth, D., and Dinn, C. 2001. Inducing malolactic fermentation in Chardonnay musts and wines using different strains of Oenococcus oeni. Aust. J. Grape Wine Res. 7, 52-59. 

Most bacteria convert malic acid to lactic acid with an intermediate formation of pyruvic acid, while Oenococcus oeni (previously classified as Leuconostoc oenos) expresses the malolactic enzyme to directly convert malic acid in one-step reaction. O. oeni has been extensively studied for controlled MLF of wine due to its higher tolerance to ethanol, low pH, and Yeasts like Schizosaccharomyces pombe and Saccharomyces strains can also convert malic acid through a maloethanolic-type fermentation. Lactic acid is less acidic than malic acid, and as a conseqnence, MLF leads to improvement of the sensory properties and biological stability of the wines. Additionally, the production of various other by-products of the MLF reaction may affect wine flavor positively. 

Rodriguez-Nogales M.J., Vila-Crespo J. and Fernandez-Fernandez E. Immobilization of Oenococcus oeni in lentikats (R) to develop malolactic fermentation in wines. Biotechnology Progress 29 (1) (2013) 60-65. 

Agouridis N., Kopsahelis N., Plessas S., Koutinas A. A. and KaneUaki M. Oenococcus oeni cells immobilized on delignilied cellulosic material for malolactic fermentation of wine. Bioresource Technology 99 (18) (2008) 9017-9020. 

Servetas I., Berbegal C., Camacho N., Bekatorou A., Ferrer S., Nigam P, Drouza C. and Koutinas A.A. Saccharomyces cerevisiae and Oenococcus oeni immobilized in different layers of a cellulose/starch gel composite for simultaneous alcoholic and malolactic wine fermentations. Process Biochemistry 48 (9) (2013) 1279-1284. 

Meanwhile, the German oenologist, Hermann Miiller-Thnrgan, introduced the concept of inocnlating wine ferments with specially selected pure yeast cultures from a species now known as S. cerevisiae. Miiller-Thurgau and Robert Koch also demonstrated that bacteria - the malolactic bacterium now known as Oenococcus oeni - and not yeast, were responsible for the reduction of malic add in wine. This process is... 

Bartowsky, E. J. (2005). Oenococcus oeni and malolactic fermentation - moving into the molecular arena. Australian Journal of Grape and Wine Research, 11, 174—187. 

Although species diversity in a must can increase shortly after crush, viable cell number normally remains relatively low (<10 to 10 CFU/mL) for some period of time (Lonvaud-Funel et al., 1991). Even if inoculated prior to alcoholic fermentation, most lactic acid bacteria experience a rapid die-off during alcoholic fermentation, commonly to populations below lOOCFU/mL. As an example, Edwards et al. (1990) observed the population of O. oeni decrease from 10 CFU/mL to less than 30CFU/mL, resulting in a delayed malolactic fermentation. Sometime after completion of alcoholic fermentation, the population of Oenococcus oeni may increase... 

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