Effect of medium composition on growth rate, growth yield and malolactic activity of Leuconostoc oenos LoZH 1-t 7-1

Abstract

The production of starter cultures for induction of malolactic fermentation in wine requires a medium which optimizes growth rate and yield and at the same time malolactic activity of the culture. Glucose and fructose are the main sugars in grape juice and wine and L-malate is an energy source which can affect growth rate and malolatic activity. The effect of these substrates were studied in a synthetic nutrient medium of pH 4.5. Growth rate and growth yield were highest in media containing fructose as carbohydrate source. Maximum cell density was reached in media containing fructose after 36 h, compared to 144 h in media containing glucose. Cell yields in media containing fructose were 160–200% higher than in media containing glucose as carbohydrate source. Molar growth yield was the same for glucose and fructose and with and without L-malate. Maximum malolactic activity of whole cells and cell-free extract was reached during early logarithmic growth phase. Metabolism of L-malate during growth increased the malolactic activity of whole cells when grown on glucose and on glucose plus fructose. In cells grown on fructose only the malolactic activity was increased but the activity of the malolactic enzyme was decreased. The metabolism of L-malate during growth in media containing glucose increased the malolactic activity of whole cells and maintained it at higher activity during late growth and early stationary phase. Best growth rate, cell yield and malolactic activity can be obtained in media containing fructose as the main carbohydrate source with added glucose and L-malate.