非表面活性剂溶胶凝胶法制备介孔干胶包埋活酵母

通过非表面活性剂溶胶凝胶法,采用海藻糖和甘油既作为保护剂又作为造孔剂,并使用羟乙基纤维素(HEC)作为添加剂以减轻凝胶过程中的收缩,成功地将酵母原位包埋在具有介孔结构的干胶中,维持了酵母的存活并探索了包埋酵母的代谢动力学与材料孔径参数改良的相关性.选择四乙氧基硅烷(TEOS)和甲基三乙氧基硅烷(MTES)共同作为前驱体,并将湿胶(含水量60%)转变为干胶(含水量10%)以增强材料,部分实现了游离酵母的抑制.通过单轴抗压强度测试说明干胶的单轴压缩强度整体上是湿胶的13倍,最低可达7.13 MPa.由平板计数法算得溶胶中的酵母浓度为1.5×108mL-1,折算成干胶粉末则为6.4×108g-1.通过对材料进行比表面积及孔隙分析和代谢动力学表征,发现了包埋酵母的代谢动力学与材料孔径参数的相关性.通过非表面活性剂法制得的干胶的比表面积可达800 m2g-1,孔体积可达0.44 cm3g-1,孔径可达2.7 nm.在此条件下,采用独立取样的统计方法,对无游离酵母的样品点进行代谢动力学表征,包埋酵母60 h内可以代谢掉发酵液中89%的葡萄糖.

ENCAPSULATION OF LIVING YEASTS IN MESOPOROUS XEROGEL VIA NON-SURFACTANT TEMPLATING SOL-GEL PROCESS

Mesoporous xerogel has been prepared by a non-surfactant sol-gel process to encapsulate living yeasts.Trehalose and glycerol are chosen as both the protective agents and pore-forming agents.Hydroxyethylcellulose(HEC),an additive,is utilized to reduce the shrinkage of gel during drying process.The encapsulated yeasts survived in the xerogel and maintained the capability to assimilate glucose.The relationship between the yeast metabolic kinetics and the xerogel pore parameters was investigated.With tetraethoxysilane(TEOS) and methyl triethoxysilane(MTES) as precursors for reinforcing the material and transforming the hydrogel(60%moisture content) to xerogel(10%moisture content),the leakage of the yeasts is partially prevented.Through the uniaxial compressive strength test,the strength of xerogel can reach 7.13 MPa at least,which is twelve times more than that of the hydrogels.According to plate count method,the concentration of yeasts was about 1.5×108 mL-1 in sol and 6.4×108 g-1 in xerogel.Through the characterization of the specific surface area,pore structure and the yeast metabolic kinetics,we found that the metabolic dynamics of entrapped yeast was related to the pore parameters of silica matrix.The xerogel obtained by non-surfactant process could have the specific surface area of 800 m2g-1,the pore volume of 0.44 cm3g-1 and the pore diameter of 2.7 nm.Under such conditions,calculated from independent samples without free yeasts,statistically,the encapsulated yeasts can metabolize 89% glucose of the culture medium in 60 h.