Expression of amino acid converting enzymes and production of volatile compounds by Lactococcus lactis IFPL953

Abstract

Lactococcus lactis contains a large number of key enzymes responsible for the formation of volatile compounds characteristic of cheese flavour. In the present work we have investigated the expression of genes codifying amino acid converting enzymes (AACE) and the formation of volatile compounds by L. lactis IFPL953 and its mutant lacking the hydroxy acid dehydrogenase PanE (L. lactis IFPL953ΔpanE). The growth in absence of isoleucine was the main induction factor in the expression of araT, bcaT, panE, and kivD. The expression of the gdh gene of L. lactis IFPL953ΔpanE increased remarkably during the stationary growth phase, particularly under isoleucine and valine starvation conditions. L. lactis IFPL953ΔpanE showed an enhanced formation of 2- and 3-methylbutanal and their corresponding alcohols and an increase in the formation of ketones. These findings contribute to a better knowledge of L. lactis AACE regulation and its potential application in cheese flavour formation.