J. MICROENCAPSULATION, 1994, VOL. 11, NO. 2, 189-195 zyxw Microencapsulation of zyxw Lactococcus Zactis subsp. cremoris B. C. LARISCH-f, D. PONCELET-f, C. P. CHAMPAGNES and R. J. NEUFELD*-f Department of Chemical Engineering, McGill University, 3480 University St, Montrkal, QuCbec, H3A 2A7, Canada zyx $ Centre de Recherche et de DCveloppement sur les Aliments, Saint-Hyacinthe, Qukbec, J2S 8E3, Canada (Received zyxwvuts 8 October 1992; accepted 12 November 1992) Lactococcus lactis subsp. cremoris was microencapsulated within alginate/poly-L- lysine (alg/PLL), nylon or crosslinked polyethyleneimine (PEI) membranes. Toxic effects were observed with solvents and reagents used in nylon and PEI membrane formation. Alg/PLL encapsulation resulted in viable and active cell preparations which acidified milk at a rate proportional to the cell concentration, but at rates less than that of free cell preparations. At 4 X lo8 colony-forming units (cfulml milk), encapsulated cells took 17 per cent longer than free lactococci to reduce the pH of milk to 5.5. Similar activities of free and micro- encapsulated cells may be attained at higher cell concentrations ( lo9 cfu/ml milk). The rate of lactic acid production was approximately 2mmol/h at an encapsulated cell concentration of 4 X 10' cfulml. Immobilization of lactic starter cultures is of interest to the dairy industry since it facilitates cell removal, improving the control of the fermentation process (Champagne and C8tC 1987, Champagne 1990). Since cells can be recovered and reused, high inoculation rates are possible reducing fermentation time (Champagne and Chi. 1987, Champagne et al. 1988a, 1989). In general, immobilization tends to stabilize cells, potentially enhancing viability and stability in the production, storage and handling of lactic cultures (Kim et zyxwv al. 1988). In some food formulations, immobilized cells are more active than free cells (Kearney et al. 1990). Microencapsulation involves immobilization within an ultrathin, semiperme- able membrane. Cells are retained within the encapsulating membrane, potentially reducing cell loss as observed when lactic cultures were immobilized within alginate beads (Champagne and C8te 1987, Kolot 1988). Low molecular weight materials, including milk sugars and metabolic products, are free to diffuse through the membrane. One potential benefit may be in the protection of production cultures from phage contamination (Champagne et al. 1988 b, Steenson et al. 1987). Alginate has been widely applied in the immobilization of lactic acid bacteria (Linko 1985) due to the simplicity of the technique, and gentle conditions. However alginate gels are unstable in high-phosphate media (Morin et al. 1992), and cell release from the gels is undesirable in some applications (Champagne et al. 1992). Thus other immobilization techniques are of interest. Microencapsulation via interfacial polymerization can be problematic for whole cell immobilization due to the use of toxic solvents and extremes of pH during membrane formation. The objective of the present study was to microencapsulate *To whom correspondence should be addressed. 0265-2048/94 $1000 0 1994 Taylor & Francis Ltd Journal of Microencapsulation Downloaded from informahealthcare.com by Dr Denis Poncelet on 06/21/12 For personal use only.