聚乙烯醇质量浓度对复合载体固定化热带假丝酵母颗粒强度、形貌与木糖醇发酵的影响  

Effect of PVA Concentration on Mechanical Strength,Morphology and Xylitol Production of Immobilized Candida tropicalis

作　　者：邓立红[1] 蒋建新[1] 姚思宇[1] 

机构地区：[1]北京林业大学材料科学与技术学院,北京100083

出　　处：《食品科学》2011年第23期210-214,共5页Food Science

基　　金：国家自然科学基金项目(31070510);中央高校基本科研业务费专项基金项目(YX2010-11)

摘　　要：以聚乙烯醇(PVA)与海藻酸钠这两种载体复合包埋热带假丝酵母细胞,制备成固定化细胞颗粒,研究PVA质量浓度对细胞颗粒的磷酸盐耐受性、机械强度与机械稳定性、形貌及木糖醇发酵性能的影响。磷酸盐耐受性实验结果显示,提高PVA质量浓度能有效改善细胞颗粒的磷酸盐耐受性。对细胞颗粒机械强度的分析表明:发酵前所有的细胞颗粒均有较好的机械强度;但是PVA质量浓度偏低时,发酵后颗粒的机械强度大幅度下降;PVA质量浓度提高到60g/L时,细胞颗粒的机械稳定性较好,发酵后能保持较高的机械强度。扫描电镜分析表明:发酵后的细胞颗粒表面出现破裂或小孔,致使产生游离细胞,但游离细胞的量并非随颗粒机械强度的增加而减少;PVA质量浓度变化对细胞在颗粒中的分布、形态和木糖醇发酵性能影响很大;PVA质量浓度较低时,固定化细胞颗粒外层细胞密布,颗粒中心也有较多细胞,细胞呈饱满的卵圆形;随PVA质量浓度增加,颗粒内部的细胞逐渐减少;PVA质量浓度达到60g/L以上时,细胞主要分布在颗粒外层,且呈现聚集生长的现象,部分细胞发生变形;PVA质量浓度在40～60g/L时,获得了较高的木糖醇得率,约0.6g/g,但是木糖消耗速率较慢。PVA and sodium alginate were mixed to entrap Candida tropicalis cells.The effect of PVA concentration on phosphate tolerance,mechanical strength,morphology and xylitol production of the immobilized cell pellets was discussed.The results indicated that increasing PVA concentration could effectively improve phosphate tolerance of the immobilized cell pellets.All the cell pellets had good mechanical strength before fermentation,which dramatically decreased at lower PVA concentrations but showed good stability at the PVA concentration of 60 g/L,even after fermentation.Transmission scanning microscopic observations showed obvious rupture and holes as well as the resulting free cells on the surface of the immobilized cell pellets.The amount of free cells did not exhibit a decrease with increasing mechanical strength.Instead,the smallest amount of free cells was observed when PVA concentration was 50 g/L.Therefore,PVA concentration could greatly affect the distribution,morphology and xylitol production of Candida tropicalis cells.When PVA concentration was lower,mounting cells could be observed on the surface and in the center of the pellets in full round or oval shape.Increasing PVA concentration resulted in a decrease of the cell amount in the center of the pellets.When PVA concentration was higher than 60 g/L,the cells were mainly located in the outer layer with the aggregation and partially deformed cells in the caves.Xylose consumption and xylitol accumulation were also significantly affected by PVA concentration.When PVA concentration was in the range of 40-60 g/L,the yield of xylitol from xylose could reach up to 0.6 g/g in a slow xylose consumption manner.

关 键 词：聚乙烯醇 海藻酸钠 热带假丝酵母 木糖醇 

分 类 号：TQ921.7[轻工技术与工程—发酵工程]