Nutritional requirements of <i>Leuconostoc mesenteroides</i> subsp. <i>mesenteroides</i> and subsp. <i>dextranicum</i> for growth in milk

Abstract

Growth of Leuconostoc mesenteroides in milk was studied with respect to the proteinase and peptidase activities of the strains and their nutritional requirements. Ln. mesenteroides grew poorly in milk since none of the 14 strains studied exceeded 5×10 8 cfu/ml at the end of growth. Few strains displayed proteinase activity, and this did not contribute much to growth. The pattern of peptidase activities varied with the strain. Nitrogen starvation and a high requirement for Mn 2+ were involved in the cause of growth deficiencies. Addition of amino acids, 50 mg Mg 2+ /l and 0·08–0·49 mg Mn 2+ /l stimulated growth of most leuconostoc strains up to 5×10 8 cfu/ml. Addition of 5 g glucose/l to milk containing amino acids, Mg 2+ and Mn 2+ or yeast extract stimulated the growth of seven and eight strains respectively up to 10 9 cfu/ml. No growth advantage was found in a N 2 atmosphere. However, the addition of small amounts of Mn 2+ to milk suppressed the inhibitory effect of aeration on the growth of Ln. mesenteroides UD23, suggesting a protective role of Mn 2+ against O 2 toxicity.