THE METABOLISM OF SUGAR AND MALIC-ACID BY LEUCONOSTOC-OENOS - EFFECT OF MALIC-ACID, PH AND AERATION CONDITIONS

The co-metabolism of sugars by Leuconostoc oenos was studied under different environmental conditions. Under aerobic conditions, growth and sugar metabolism were poorer than under CO2 or N-2 atmosphere and acetic acid accumulated to a larger extent. Glycerol was found in the aerobic cultures while erythritol was detected under N-2 or CO2. When medium conditions make growth difficult (low pH, aerobic conditions, low nutrients), sugars were only slightly metabolized and growth was very slow while malic acid was rapidly and completely degraded, leading to an increase in the Y-ATP. Aeration effects on the malic acid degradation rate depended on the nutrients and carbon source in the medium. Malic acid clearly stimulated bacterial growth, allowing an increase in the molar growth yields and ATP production. The results suggest that under adverse conditions cells are not able to grow and malic degradation supplies additional energy production.