在分批培养和连续培养中，通过自由和固定化的蜡状芽孢杆菌 NRC7 细胞合成环糊精葡萄糖基转移酶。

Biosynthesis of cyclodextrin glucosyltransferase by the free and immobilized cells of Bacillus cereus NRC7 in batch and continuous cultures.

机构信息

Department of Chemistry of Natural and Microbial Products, National Research Center, Dokki, Cairo, Egypt.

出版信息

J Appl Microbiol. 2011 Nov;111(5):1129-37. doi: 10.1111/j.1365-2672.2011.05136.x. Epub 2011 Oct 4.

DOI:10.1111/j.1365-2672.2011.05136.x

PMID:21883731

Abstract

AIMS

The objective of this study was to enhance the production of cyclodextrin glucanotransferase (CGTase) produced by a local isolate Bacillus cereus NRC7.

METHODS AND RESULTS

In batch culture, maximal CGTase activity (69·0 U ml(-1)) was reached after 24-h incubation period. In continuous production of CGTase by the free cells of B. cereus NRC7, maximal reactor productivity (11·76 KU l(-1) h(-1)), with enzyme concentration of 49·0 U ml(-1) and specific productivity of 904·6 U per g wet cells per h, was attained at dilution rate of 0·24 h(-1), over a period of 640 h. Bacillus cereus NRC7 cells were immobilized on chitosan. The immobilization conditions with respect to matrix concentration and maximal cell loading were optimized for maximal CGTase production. In repeated batch operation, the activity of the immobilized cells was stable during ten cycles and the activity remained between 51 and 55 U ml(-1). In packed-bed reactor, the immobilized cells showed maximal productivity (27·18 KU l(-1) h(-1)) with enzyme concentration of 54·63 U ml(-1) and specific productivity of 151·89 U per g wet cells per h at dilution rate of 0·5 h(-1). The half-life of the immobilized cells was higher than 20 days.

CONCLUSIONS

Continuous fermentation by the immobilized cells in packed-bed reactor is an appropriate potential technique for B. cereus NRC7 CGTase production that gave maximum productivity (27·18 KU l(-1) h(-1)), which was 9·47-, 2·31-, 12·24- and 12·94-fold higher than the free cells in batch, free cells in continuous, immobilized cells in batch and repeated batch cultures, respectively.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study that evaluates CGTase productivity, in different fermentation modes, in terms of specific productivity (U per gram cells per h). In continuous fermentation by immobilized cells, maximal levels of CGTase productivity are higher than the previously reported values.

摘要

目的

本研究的目的是提高由本地分离的蜡状芽孢杆菌 NRC7 产生的环糊精葡萄糖基转移酶（CGTase）的产量。

方法和结果

在分批培养中，24 小时培养后达到最大 CGTase 活性（69.0 U ml(-1)）。在自由细胞的连续生产中蜡状芽孢杆菌 NRC7 的 CGTase，最大反应器生产力（11.76 KU l(-1) h(-1)），酶浓度为 49.0 U ml(-1)和比生产率为 904.6 U per g 湿细胞 per h，在稀释率为 0.24 h(-1)，640 小时内达到。蜡状芽孢杆菌 NRC7 细胞固定在壳聚糖上。优化了基质浓度和最大细胞负载的固定化条件，以获得最大的 CGTase 产量。在重复分批操作中，在十个循环中固定化细胞的活性保持稳定，活性保持在 51 到 55 U ml(-1)之间。在填充床反应器中，固定化细胞在稀释率为 0.5 h(-1)时表现出最大的生产率（27.18 KU l(-1) h(-1)），酶浓度为 54.63 U ml(-1)和比生产率为 151.89 U per g 湿细胞 per h。固定化细胞的半衰期高于 20 天。

结论

填充床反应器中固定化细胞的连续发酵是一种合适的潜在技术，可用于蜡状芽孢杆菌 NRC7 CGTase 的生产，可获得最大的生产率（27.18 KU l(-1) h(-1)），分别比分批培养中的游离细胞、连续培养中的游离细胞、分批培养中的固定化细胞和重复分批培养中的游离细胞高 9.47、2.31、12.24 和 12.94 倍。