Media sterilization procedures were studied during the production of a starter culture, Leuconostoc oenos 40·40, for use in malolactic fermentation of wine. Heat and filter sterilization of yeast extract was compared with respect to the growth of L. oenos. Addition of a mixture of vitamins after heat sterilization of basal medium with yeast extract stimulated the growth of this organism. When used alone, each vitamin except nicotinic acid had a stimulatory effect on growth. During pilot fermentation the production of bacterial cells per hour was doubled when vitamins were supplemented after sterilization of medium. Vitamin supplementation also increased the viability of lyophilized cells.