Camelin I, Lacroix C, Paquin C, Prévost H, Cachon R, Divies C
Laboratoire de Microbiologie, ENS BANA, Université de Bourgogne, Dijon, France.
Biotechnol Prog. 1993 May-Jun;9(3):291-7. doi: 10.1021/bp00021a008.
The effect of various concentrations of sequestrants (sodium citrate, sodium metaphosphate, and EDTA) was studied on gellan gel (1.5-2.5% (w/v)) setting temperature and rheological properties. Addition of EDTA between 0 and 0.8% (w/v) led to a progressive decrease of setting temperature. Citrate and metaphosphate decreased this parameter when added up to 0.4 or 0.6%, depending on gellan gum concentration, eventually resulting in the absence of gel formation at room temperature for the 1.5% gellan solution containing 0.4% citrate. This effect was accompanied by a significant decrease of gel strength and stiffness and might be attributed to the binding of the divalent cations required for chain association during gelation by chelatants. With the aim of lowering the gel setting temperature during the cell entrapment process while maintaining high mechanical properties, a gel made of 2.5% gellan gum and 0.2% sodium citrate was used to entrap Bifidobacterium longum ATCC 15707. Ions and pH of the inoculum during the immobilization step influenced the long-term mechanical stability of the gel beads during continuous fermentation in a stirred tank reactor. High stability as well as high biocatalyst activity was obtained when a washed cell suspension was used as the inoculum. Gellan gel produced by dissolving gellan gum in a sodium citrate solution may be a promising entrapment matrix for temperature-sensitive cells such as mesophilic lactic acid bacteria and eukaryotic cells.
研究了不同浓度的螯合剂（柠檬酸钠、偏磷酸钠和乙二胺四乙酸）对结冷胶（1.5 - 2.5%（w/v））凝固温度和流变特性的影响。添加0至0.8%（w/v）的乙二胺四乙酸会导致凝固温度逐渐降低。根据结冷胶的浓度，添加至0.4%或0.6%的柠檬酸盐和偏磷酸盐会降低该参数，最终导致含有0.4%柠檬酸盐的1.5%结冷胶溶液在室温下无法形成凝胶。这种效应伴随着凝胶强度和硬度的显著降低，可能归因于螯合剂在凝胶形成过程中与链缔合所需的二价阳离子结合。为了在细胞包埋过程中降低凝胶凝固温度同时保持较高的机械性能，使用由2.5%结冷胶和0.2%柠檬酸钠制成的凝胶来包埋长双歧杆菌ATCC 15707。固定化步骤中接种物的离子和pH值会影响搅拌罐反应器中连续发酵过程中凝胶珠的长期机械稳定性。当使用洗涤后的细胞悬浮液作为接种物时，可获得高稳定性以及高生物催化剂活性。通过将结冷胶溶解在柠檬酸钠溶液中制备的结冷胶凝胶可能是用于包埋嗜温乳酸菌和真核细胞等对温度敏感细胞的一种有前景的包埋基质。
