Chitin and its derivatives have wide sources and biosafety,which showed well application prospect in the fields of material,food,and chemical industry. This study firstly attempted to immobilize nitrilase-producing resting cells ofG. intermedia using surface activated chitin as the material. The immobilization conditions were primarily optimized. 3% of modified chitin,7% of sodium tripolyphosphate,5h of immobilization time and 20g/L of biomass were used as the suitable condition with the highest nitrilase activity displayed. The catalytic performance of immobilized cells was characterized for 4-cyanopyridine biotransformation. The results showed that the optimum temperature,pH,and substrate concentration were 50℃,7.0,and 125mmol/L,respectively. Also, the maximum tolerance toward product concentration was 400mmol/L. These characteristics of immobilized cells demonstrated obvious advantages over corresponding resting cells. Furthermore,the immobilized cells were used for the biotransformation of 4-cyanopyridine into isonicotinic acid. The immobilized cells could be reused for 14 batches,while the resting cells only conducted 3 batches.%甲壳素及其衍生物资源来源广泛、具有生物安全性，在材料、食品、化工等领域拥有良好的应用前景。本研究首次尝试采用经表面活化的甲壳素为包埋材料对产腈水解酶的G. intermedia游离细胞进行固定化，对固定化条件进行了初步优化，选取甲壳素质量分数3%，三聚磷酸钠质量分数7%，固定化时间5 h，固定菌体浓度为20g/L时催化活力达到最高。对固定化细胞的催化应用特性进行了表征，结果表明固定化细胞对4-氰基吡啶转化反应的最适反应温度为50℃，最适pH值为7.0；最适底物浓度为125mmol/L，最大产物耐受浓度为400mmol/L，均明显优于游离细胞。探索了将制备的固定化细胞直接应用于4-氰基吡啶生物转化合成异烟酸，固定化细胞可重复利用14批次，而相应游离细胞仅为3次。
展开▼
