Laboratory of Food Biotechnology, Institute of Food Science and Nutrition, Zurich, Switzerland.
J Microencapsul. 2010;27(1):1-9. doi: 10.3109/02652040802217516.
Silk fibroin was evaluated as a new matrix for immobilized cell fermentation. Silk fibroin was extracted from Bombyx mori cocoon, purified, concentrated in polyethylene glycol solution and diluted to 3 wt% with distilled water. This fibroin solution was used to encapsulate sensitive cells of the probiotic strain, Bifidobacterium longum ATCC 15707. Polymer droplets produced with an encapsulator were collected in liquid nitrogen and lyophilized. A low overall survival of 0.2% was measured after lyophilization. Lyophilized beads were hardened for 24 h under vacuum with an atmosphere of 89% relative humidity. The inoculated beads were colonized in two successive batch fermentations. Structure of silk fibroin beads and colonization of cells were examined with scanning electron microscopy. Colonized beads were tested in continuous fermentations for cell production. A biomass productivity of 1.7 x 10(9) CFU ml(-1) h(-1) was achieved, which was limited by loss of bead structure. This instability might be due to bead degradation by proteolytic activity of cells and/or limited mechanical stability during continuous fermentation in the stirred tank reactor.
丝素蛋白被评估为固定化细胞发酵的新型基质。丝素蛋白从家蚕茧中提取，经过纯化、在聚乙二醇溶液中浓缩，并用水稀释至 3wt%。将这种丝素溶液用于包封益生菌菌株长双歧杆菌 ATCC 15707 的敏感细胞。用包封器产生的聚合物液滴在液氮中收集并冻干。冻干后总体存活率仅为 0.2%。冻干珠粒在相对湿度为 89%的真空下硬化 24 小时。接种珠粒在连续批次发酵中定植。用扫描电子显微镜检查丝素珠粒的结构和细胞定植。对连续发酵中的细胞产率进行了测试。实现了 1.7×10(9)CFU ml(-1) h(-1)的生物量生产力，这受到珠粒结构损失的限制。这种不稳定性可能是由于细胞的蛋白水解活性导致珠粒降解和/或在搅拌釜式反应器中的连续发酵过程中机械稳定性有限。
