Champagne C P, Gaudy C, Poncelet D, Neufeld R J
Centre de Recherche et de Développement sur les Aliments, Agriculture Canada, Saint-Hyacinthe, Québec.
Appl Environ Microbiol. 1992 May;58(5):1429-34. doi: 10.1128/aem.58.5.1429-1434.1992.
Cell release during milk fermentation by Lactococcus lactis immobilized in calcium alginate beads was examined. Numbers of free cells in the milk gradually increased from 1 x 10(6) to 3 x 10(7) CFU/ml upon successive reutilization of the beads. Rinsing the beads between fermentations did not influence the numbers of free cells in the milk. Cell release was not affected by initial cell density within the beads or by alginate concentration, although higher acidification rates were achieved with increased cell loading. Coating alginate beads with poly-L-lysine (PLL) did not significantly reduce the release of cells during five consecutive fermentations. A double coating of PLL and alginate reduced cell release by a factor of approximately 50. However, acidification of milk with beads having the PLL-alginate coating was slower than that with uncoated beads. Immersing the beads in ethanol to kill cells on the periphery reduced cell release, but acidification activity was maintained. Dipping the beads in aluminum nitrate or a hot CaCl2 solution was not as effective as dipping them in ethanol. Ethanol treatment or heating of the beads appears to be a promising method for maintaining acidification activity while minimizing viable cell release due to loosely entrapped cells near the surface of the alginate beads.
研究了固定在海藻酸钙珠中的乳酸乳球菌在牛奶发酵过程中的细胞释放情况。随着珠子的连续重复利用，牛奶中游离细胞的数量从1×10⁶逐渐增加到3×10⁷CFU/ml。在发酵之间冲洗珠子不会影响牛奶中游离细胞的数量。细胞释放不受珠子内初始细胞密度或海藻酸盐浓度的影响，尽管随着细胞负载量的增加，酸化速率更高。用聚-L-赖氨酸（PLL）包被海藻酸钙珠在连续五次发酵过程中不会显著减少细胞释放。PLL和海藻酸盐的双重包被使细胞释放减少了约50倍。然而，用具有PLL-海藻酸盐包被的珠子酸化牛奶比用未包被的珠子慢。将珠子浸入乙醇中以杀死外周细胞可减少细胞释放，但酸化活性得以维持。将珠子浸入硝酸铝或热的氯化钙溶液中不如浸入乙醇有效。乙醇处理或加热珠子似乎是一种有前景的方法，可以在保持酸化活性的同时，将由于海藻酸钙珠表面附近细胞包埋不紧密而导致的活细胞释放降至最低。
