THE DEGRADATION OF MALIC-ACID BY HIGH-DENSITY CELL-SUSPENSIONS OF LEUCONOSTOC-OENOS

Washed cell suspensions of Leuconostoc oenos catalysed the degradation of L-malic acid to L-lactic acid. Cell suspensions of 10(10) cfu ml(-1) degraded 90-95% of the malic acid in a buffer assay system and in wine within 30 min. A reaction time of 6 h was needed to obtain the same extent of degradation with suspensions of 10(9) cfu ml(-1) With a reaction period of 6 h and an initial malic acid concentration of 3 g l(-1), reaction variables of pH 2.5-4.0, temperature 10-30 degrees C, ethanol up to 15%, and L-lactic acid up to 4 g l(-1) did not decrease the degradation of malic acid to below 90-95%. Total SO2 at 100 mg l(-1) decreased the degradation of malic acid to 80%. The degradation (%) of malic acid was decreased when the concentration of malic acid was decreased below 2 g l(-1). The results indicate the prospect of using high densities of Leuc. oenos cells in membrane bioreactor systems for the rapid, continuous, deacidification of wine.