ENCAPSULATION OF LACTOBACILLUS-CASEI CELLS IN LIQUID-CORE ALGINATE CAPSULES FOR LACTIC-ACID PRODUCTION

The immobilization method of Lactobacillus casei cells was investigate d using alginate capsules that possess an interphasic membrane and a l iquid core. The capsules were found to offer more space for cellular g rowth than gel-core beads, which resulted in 1.5-fold higher cell conc entration than in the latter; however the Ca-alginate structure was un stable during repeated batch fermentations for lactic acid production. Ba-alginate capsules were chemically and physically more stable than Ca-alginate capsules in phosphate and lactate solutions. Attempts were also made to use various hardening agents to stabilize the structure of the Ba-alginate capsules. It was found that the treatment with a mi xture of chitosan and BaCl2 solution gave the best results for hardeni ng. Finally, stable lactic acid production was possible with a product ivity of more than 2.7 gl(-1)h(-1) by L. casei cells immobilized in ch itosan-coated Ba-alginate capsules. The cell leakage from the capsules was maintained relatively low during batch fermentations.