Juan Wang1, Jing Zhang1, Lu Wang1, Hong Liu1, Ning Li2, Huanxia Zhou2, Zhanguo Ning2, Weican Zhang1, Lushan Wang1, Feng Huang3, Yaohua Zhong4. 1. State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, People's Republic of China. 2. Shandong Xingguang Sugar Group Co. Ltd, Laoling, Dezhou, 253600, People's Republic of China. 3. State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, People's Republic of China. fhuang@sdu.edu.cn. 4. State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao, 266237, People's Republic of China. zhongyaohua@sdu.edu.cn.
Abstract
OBJECTIVE: To achieve continuous production of fructooligosaccharides (FOS) by recycling of the mycelial cells containing the thermal-stable β-fructofuranosidase in Aspergillus niger without immobilization. RESULTS: The thermal-stable β-fructofuranosidase FopA-V1 was successfully expressed in A. niger ATCC 20611 under the control of the constitutive promoter PgpdA. The engineered A. niger strain FV1-11 produced the β-fructofuranosidase with improved thermostability, which remained 91.2% of initial activity at 50 °C for 30 h. Then its mycelial β-fructofuranosidase was recycled for the synthesis of FOS. It was found that the enzyme still had 79.3% of initial activity after being reused for six consecutive cycles, whereas only 62.3% β-fructofuranosidase activity was detected in the parental strain ATCC 20611. Meanwhile, the FOS yield of FV1-11 after six consecutive cycles reached 57.1% (w/w), but only 51.0% FOS yield was detected in ATCC 20611. CONCLUSIONS: The thermal-stable β-fructofuranosidase produced by A. niger can be recycled to achieve continuous synthesis of FOS with high efficiency, providing a powerful and economical strategy for the industrial production of FOS.
OBJECTIVE: To achieve continuous production of fructooligosaccharides (FOS) by recycling of the mycelial cells containing the thermal-stable β-fructofuranosidase in Aspergillus niger without immobilization. RESULTS: The thermal-stable β-fructofuranosidase FopA-V1 was successfully expressed in A. niger ATCC 20611 under the control of the constitutive promoter PgpdA. The engineered A. niger strain FV1-11 produced the β-fructofuranosidase with improved thermostability, which remained 91.2% of initial activity at 50 °C for 30 h. Then its mycelial β-fructofuranosidase was recycled for the synthesis of FOS. It was found that the enzyme still had 79.3% of initial activity after being reused for six consecutive cycles, whereas only 62.3% β-fructofuranosidase activity was detected in the parental strain ATCC 20611. Meanwhile, the FOS yield of FV1-11 after six consecutive cycles reached 57.1% (w/w), but only 51.0% FOS yield was detected in ATCC 20611. CONCLUSIONS: The thermal-stable β-fructofuranosidase produced by A. niger can be recycled to achieve continuous synthesis of FOS with high efficiency, providing a powerful and economical strategy for the industrial production of FOS.