Enhancing fructooligosaccharides production by genetic improvement of the industrial fungus Aspergillus niger ATCC 20611.
Aspergillus niger ATCC20611 is one of the most potent filamentous fungi used commercially for production of fructooligosaccharides (FOS), which are prospective components of functional food by stimulating probiotic bacteria in the human gut. However, current strategies for improving FOS yield still rely on production process development. The genetic engineering approach hasn't been applied in industrial strains to increase FOS production level. Here, an optimized polyethylene glycol (PEG)-mediated protoplast transformation system was established in A. niger ATCC 20611 and used for further strain improvement. The pyrithiamine resistance gene (ptrA) was selected as a dominant marker and protoplasts were prepared with high concentration (up to 108g-1wet weight mycelium) by using mixed cell wall-lysing enzymes. The transformation frequency with ptrA can reach 30-50 transformants per μg of DNA. In addition, the efficiency of co-transformation with the EGFP reporter gene (egfp) was high (approx. 82%). Furthermore, an activity-improved variant of β-fructofuranosidase, FopA(A178P), was successfully overexpressed in A. niger ATCC 20611 by using the transformation system. The transformant, CM6, exhibited a 58% increase in specific β-fructofuranosidase activity (up to 507U/g), compared to the parental strain (320U/g), and effectively reduced the time needed for completion of FOS synthesis. These results illustrate the feasibility of strain improvement through genetic engineering for further enhancement of FOS production level.
State Key Laboratory of Microbial Technology, School of Life Sciences, Shandong University, Jinan 250100, PR China.
Jing
J
Zhang
Shandong Xingguang Sugar Group Co., Ltd., Laoling, Dezhou, 253600, PR China.
Caixia
C
Liu
State Key Laboratory of Microbial Technology, School of Life Sciences, Shandong University, Jinan 250100, PR China.
Yijia
Y
Xie
Shandong Academy of Pharmaceutical Sciences, Jinan 250101, PR China.
Ning
N
Li
Shandong Academy of Pharmaceutical Sciences, Jinan 250101, PR China.
Zhanguo
Z
Ning
Key Laboratory of Colloid and Interface Chemistry of the Education Ministry of China, Shandong University, Jinan 250100, PR China.
Na
N
Du
Key Laboratory of Colloid and Interface Chemistry of the Education Ministry of China, Shandong University, Jinan 250100, PR China.
Xirong
X
Huang
State Key Laboratory of Microbial Technology, School of Life Sciences, Shandong University, Jinan 250100, PR China. Electronic address: zhongyaohua@sdu.edu.cn.
Yaohua
Y
Zhong
D001234:Aspergillus niger / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D005818:Genetic Engineering / Q000379:methods*; D007218:Industrial Microbiology; D009844:Oligosaccharides / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D010957:Plasmids; D011523:Protoplasts; D014170:Transformation, Genetic
D009844:Oligosaccharides; C116580:fructooligosaccharide
Aspergillus niger; Fructooligosaccharide; Genetic engineering; Transformation system