The degradation of malic acid by high density cell suspensions of <i>Leuconostoc oenos</i>

Abstract

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 1 ‐1 , reaction variables of pH 2.5‐4.0, temperature 10–30°C, ethanol up to 15%, and L‐lactic acid up to 4 g 1 ‐1 did not decrease the degradation of malic acid to below 90–95%. Total SO 2 at 100 mg 1 ‐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 1 ‐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.