The development of the malolactic fermentation, bioconversion Of L-malic ac
id to L-lactic acid, is a difficult and time-consuming process that does no
t always proceed favorably under the natural conditions of wine. Traditiona
l fermentations are used worldwide to produce high-quality wines, although
delay or failure is not an unusual outcome. During recent years several tec
hnologies have been proposed to induce biological deacidification of wines
by using, malolactic bacteria, principally Oenococcus oeni and Lactobacillu
s sp. These alternative technologies usually involve the use of high densit
ies of cells or enzymes, free or immobilized onto different matrices. Immob
ilization materials, several types of bioreactors, and the properties of ma
ny specific systems are discussed in this review.