Research

High yield recombinant thermostable α-amylase production using an improved Bacillus licheniformis system

Dandan Niu^1,3 , Zhirui Zuo¹ , Gui-Yang Shi^1,2 and Zheng-Xiang Wang^1,2

¹  Center for Bioresource and Bioenergy, School of Biotechnology & Culture and Information Center of Industrial Microorganisms of China Universities, Jiangnan University, Wuxi 214122, PR China

²  The Key Laboratory of Industrial Biotechnology, Ministry of Education, Wuxi 214122, PR China

³  Institute for Wine Biotechnology, University of Stellenbosch, Matieland 7602, South Africa

author email corresponding author email

Microbial Cell Factories 2009, 8:58doi:10.1186/1475-2859-8-58

Published:	31 October 2009

Abstract

Background

Some strains of Bacillus licheniformis have been improved by target-directed screening as well as by classical genetic manipulation and used in commercial thermostable α-amylase and alkaline protease production for over 40 years. Further improvements in production of these enzymes are desirable.

Results

A new strain of B. licheniformis CBBD302 carrying a recombinant plasmid pHY-amyL for Bacillus licheniformis α-amylase (BLA) production was constructed. The combination of target-directed screening and genetic recombination led to an approximately 26-fold improvement of BLA production and export in B. licheniformis. Furthermore, a low-cost fermentation medium containing soybean meal and cottonseed meal for BLA production in shake-flasks and in a 15 liter bioreactor was developed and a BLA concentration of up to 17.6 mg per ml growth medium was attained.

Conclusion

This production level of BLA by B. licheniformis CBBD302(pHY-amyL) is amongst the highest levels in Gram-positive bacteria reported so far.