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J Biotechnol. 2017 Jul 10;253:1-9. doi: 10.1016/j.jbiotec.2017.05.011. Epub 2017 May 12.

Rewiring the reductive tricarboxylic acid pathway and L-malate transport pathway of Aspergillus oryzae for overproduction of L-malate.

Author information

1
Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China.
2
Hangzhou Bioking Biochemical Engineering Co. Ltd, Hangzhou 311106, China.
3
School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
4
Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China. Electronic address: lijianghua@jiangnan.edu.cn.
5
Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China.
6
Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China. Electronic address: longliu@jiangnan.edu.cn.

Abstract

Aspergillus oryzae finds wide application in the food, feed, and wine industries, and is an excellent cell factory platform for production of organic acids. In this work, we achieved the overproduction of L-malate by rewiring the reductive tricarboxylic acid (rTCA) pathway and L-malate transport pathway of A. oryzae NRRL 3488. First, overexpression of native pyruvate carboxylase and malate dehydrogenase in the rTCA pathway improved the L-malate titer from 26.1gL-1 to 42.3gL-1 in shake flask culture. Then, the oxaloacetate anaplerotic reaction was constructed by heterologous expression of phosphoenolpyruvate carboxykinase and phosphoenolpyruvate carboxylase from Escherichia coli, increasing the L-malate titer to 58.5gL-1. Next, the export of L-malate from the cytoplasm to the external medium was strengthened by overexpression of a C4-dicarboxylate transporter gene from A. oryzae and an L-malate permease gene from Schizosaccharomyces pombe, improving the L-malate titer from 58.5gL-1 to 89.5gL-1. Lastly, guided by transcription analysis of the expression profile of key genes related to L-malate synthesis, the 6-phosphofructokinase encoded by the pfk gene was identified as a potential limiting step for L-malate synthesis. Overexpression of pfk with the strong sodM promoter increased the L-malate titer to 93.2gL-1. The final engineered A. oryzae strain produced 165gL-1 L-malate with a productivity of 1.38gL-1h-1 in 3-L fed-batch culture. Overall, we constructed an efficient L-malate producer by rewiring the rTCA pathway and L-malate transport pathway of A. oryzae NRRL 3488, and the engineering strategy adopted here may be useful for the construction of A. oryzae cell factories to produce other organic acids.

KEYWORDS:

Aspergillus oryzae; C4-dicarboxylate transporter; L-malate; Reductive tricarboxylic acid pathway

PMID:
28506930
DOI:
10.1016/j.jbiotec.2017.05.011
[Indexed for MEDLINE]

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