Sodini I, Boquien C Y, Corrieu G, Lacroix C
Laboratoire de Génie et de Microbiologie des Procédés Alimentaires, INRA, Thiverval-Grignon, France.
Enzyme Microb Technol. 1997 Apr;20(5):381-8. doi: 10.1016/s0141-0229(96)00165-2.
Four strains of mesophilic lactic acid bacteria were separately or coentrapped in kappa-carrageenan/locust bean gum gel beads and used for continuous prefermentation of UHT skim milk in a stirred-tank bioreactor. Lactic acid and cell productivities of the immobilized cell bioreactor were particularly high and remarkably stable during eight weeks of continuous milk prefermentation (about 18 g h-1 l-1 of lactic acid and 4.9 x 10(12) CFU h-1 l-1, respectively, but important variations of the bacterial populations is prefermented milk and gel beads occurred in any case (co-or separate entrapment). The strain Lactococcus lactis subsp. lactis biovar diacetylactis CDII became dominant, accounting for approx. 90% (released cells) and 78% (immobilized cells) of the total population. Microscopic observations of sections of gels beads showed a progressive destructing of the bead surface with rupture and release of entrapped viable cells from peripheral cavities of the gel. It is believed that these cavities close again after releasing all or part of their cell content, entrapping the different strains of the mixed culture and initiating a new colonization step and a cross-contamination of the beads. On the other hand, experimentations over seven-week periods with pasteurized milk showed the high resistance of the immobilized cell bioreactor to psychrotrophic contamination.
将四株嗜温乳酸菌分别或共同包埋于κ-卡拉胶/刺槐豆胶凝胶珠中，并用于搅拌罐式生物反应器中对超高温灭菌脱脂乳进行连续预发酵。在连续八周的牛奶预发酵过程中，固定化细胞生物反应器的乳酸和细胞生产力特别高且显著稳定（分别约为18 g h-1 l-1的乳酸和4.9×10(12) CFU h-1 l-1），但无论如何（共同或单独包埋），在预发酵的牛奶和凝胶珠中细菌种群都出现了重要变化。乳酸乳球菌乳酸亚种双乙酰乳酸CDII菌株成为优势菌株，分别占总菌数的约90%（释放细胞）和78%（固定化细胞）。对凝胶珠切片的显微镜观察表明，凝胶珠表面逐渐破坏，凝胶外周腔中的活细胞破裂并释放出来。据信，在释放其全部或部分细胞内容物后，这些腔会再次封闭，将混合培养物的不同菌株包埋起来，并启动新的定殖步骤和凝胶珠的交叉污染。另一方面，用巴氏杀菌牛奶进行的为期七周的实验表明，固定化细胞生物反应器对嗜冷菌污染具有高度抗性。
