Full Length Research Paper

Effect of different culture conditions for dextransucrase production in Escherichia coli using lactose as inducer

Hong-Bin Zhang¹*, Ya-Jie Wang¹, Xue-Qin Hu¹, Hui-Xia Zhu¹ and Zhao-Jun Wei²

¹Department of Pharmaceutical Engineering, Hefei University of Technology, Hefei 230009, China.

²Department of Biotechnology, Hefei University of Technology, Hefei 230009, China.

*Corresponding author. E-mail: hongbinzh@yahoo.com.cn. Tel: +86-551-2901968. Fax: +86-551-2901968.

Accepted 9 February, 2009

This study presented the effect of different culture conditions, including lactose concentration, temperature, cell density (OD₆₀₀), and media ingredients, on dextransucrase expression by lactose induction in the engineering strain Escherichia coli BL21(DE3)/pETdex. The results showed that induced medium (IM) was much more suitable for dextransucrase expression than LB medium. Optimal conditions were as follows: adding lactose of 1.0% when OD₆₀₀ reached 1.0 and continuing cultivation at 25°C for 6 h. The components and concentration of media were decided by the orthogonal experiment. Glucose was the most important negative impact factor. Besides the requirement of tryptone and yeast extract, glycerol, M9 salt solution and magnesium sulfate promoted enzyme activity. Under optimal conditions in optimized complex medium, maximal activity of the expressed enzyme reached 48.18 U/ml.

Key words: Dextransucrase, lactose, medium, components, culture conditions.