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Appl Microbiol Biotechnol. 2016 Jul;100(13):5791-803. doi: 10.1007/s00253-016-7324-z. Epub 2016 Feb 2.

The opposite roles of agdA and glaA on citric acid production in Aspergillus niger.

Wang L1, Cao Z2,3, Hou L2,3, Yin L2,3, Wang D2,3, Gao Q2,3,4, Wu Z5, Wang D6,7,8.

Author information

1
School of Biological Science and Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
2
College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, People's Republic of China.
3
Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, People's Republic of China.
4
National and Local United Engineering Lab of Metabolic Control Fermentation Technology, Tianjin, 300457, People's Republic of China.
5
School of Biological Science and Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China. btzhqwu@scut.edu.cn.
6
College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, People's Republic of China. 15620074987@163.com.
7
Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, People's Republic of China. 15620074987@163.com.
8
National and Local United Engineering Lab of Metabolic Control Fermentation Technology, Tianjin, 300457, People's Republic of China. 15620074987@163.com.

Abstract

Citric acid is produced by an industrial-scale process of fermentation using Aspergillus niger as a microbial cell factory. However, citric acid production was hindered by the non-fermentable isomaltose and insufficient saccharification ability in A. niger when liquefied corn starch was used as a raw material. In this study, A. niger TNA 101ΔagdA was constructed by deletion of the α-glucosidase-encoding agdA gene in A. niger CGMCC 10142 genome using Agrobacterium tumefaciens-mediated transformation. The transformants A. niger OG 1, OG 17, and OG 31 then underwent overexpression of glucoamylase in A. niger TNA 101ΔagdA. The results showed that the α-glucosidase activity of TNA 101ΔagdA was decreased by 62.5 % compared with CGMCC 10142, and isomaltose was almost undetectable in the fermentation broth. The glucoamylase activity of the transformants OG 1 and OG 17 increased by 34.5 and 16.89 % compared with that of TNA 101ΔagdA, respectively. In addition, for the recombinants TNA 101ΔagdA, OG 1 and OG 17, there were no apparent defects in the growth development. Consequently, in comparison with CGMCC 10142, TNA 101ΔagdA and OG 1 decreased the residual reducing sugar by 52.95 and 88.24 %, respectively, and correspondingly increased citric acid production at the end of fermentation by 8.68 and 16.87 %. Citric acid production was further improved by decreasing the non-fermentable residual sugar and increasing utilization rate of corn starch material in A. niger. Besides, the successive saccharification and citric acid fermentation processes were successfully integrated into one step.

KEYWORDS:

Aspergillus niger; Citric acid; Gene deletion; Multicopy overexpression; glaA gene; α-Glucosidase

PMID:
26837219
DOI:
10.1007/s00253-016-7324-z
[Indexed for MEDLINE]

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