Question

A winemaking guide describes “malolactic fermentation,” where malate is converted to lactic acid. Interestingly, this process can happen simultaneously with other forms of fermentation.

a. This process usually occurs across a membrane. How is this process generating energy for the cell?

Answer 1

Malolactic fermentation is a process in winemaking in which savoury tasting malic acid is converted to softer tasting lactic acid. This process is generally acomplised by Lactic acid bacteria (LAB) whose primary function is to convert L-malic acid to L+lactic acid. as an indirect means of creating energy by chemiosmosis which uses the difference in pH gradient between inside the cell and otside the wine to produce ATP. It can be explained by the fact that most of the L-malate exist in negatively charged monoanionic form in the low pH of wine. The LAB moves this anion from the wine into higher pH level of its cellular plasma membrane and while doing so, it causes a net negative charge that creates electrical potential. In malolactic fermentation, decarboxylation of malic acid into lactic acid takes place that not only releases CO2 but also consumes a proton, which generates the pH gradient via proton motive force (PMF) which in turn produce ATP. Thus, the cells derive energy with the conversion of malate to lactic acid.