COMPARISON OF THE PRODUCTION OF LACTIC-ACID BY 3 DIFFERENT LACTOBACILLI AND ITS RECOVERY BY EXTRACTION AND ELECTRODIALYSIS

D(-)-Lactic acid was produced by Lactobacillus delbrueckii DSM 20072 (A TCC 9649) (LD), L(+)-lactic acid by Lactobacillus casei subsp. rhamnosus DSM 20021 (ATCC 7469) (LC) and by Lactobacillus salivarius subsp. salivarius DSM 20492 (ATCC 11742) (LS) on MRS medium and glucose substrate homofermentatively in batch cultures. LS exhibited the highest specific growth rate (mu = 1.41 h(-1)) and the highest specific productivity (pi = 5.45 h(-1)). Acetate and citrate stimulated its growth. Substrate inhibition occurred at 30 g litre(-1) glucose for LD, 26 g litre(-1) glucose for LC, and no inhibition was observed up to 100g litre(-1) glucose for LS. 60 g litre(-1) lactate solution at pH 6 caused only slight product inhibition of LS. The product was extracted by four different amine carriers (Amberlite LA2, Hoe F2562, Hostarex A327 and Alamin 366) in the presence of modifiers (long-chain alcohols, alkylphosphates and acidic organic compounds) in kerosene and butylacetate, and a phosphinoxide (Cyanex 923). When using Hostarex A327 in oleylic alcohol or Cyanex 923 (phosphinoxide carrier) in kerosene or in oleylic alcohol, no modifier was necessary. The extent of lactic acid extraction was evaluated and the separation of lactic acid from citric and acetic acids was investigated. The re-extraction of the free acid under different conditions was not very successful. A maximum lactic acid yield of 72% was obtained. Except for kerosene and oleyl alcohol, the biocompatibility of the other chemicals was unsatisfactory. Their application for in situ extraction cannot be recommended. Recovery of the free lactic acid by electrodialysis and bipolar membrane is very promising. In situ recovery is possible.