title: Enhanced fed-batch production of pyrroloquinoline quinine in Methylobacillus sp. CCTCC M2016079 with a two-stage pH control strategy.
abstract: The effects of pH control strategy and fermentative operation modes on the biosynthesis of pyrroloquinoline quinine (PQQ) were investigated systematically with Methylobacillus sp. CCTCC M2016079 in the present work. Firstly, the shake-flask cultivations and benchtop fermentations at various pH values ranging from 5.3 to 7.8 were studied. Following a kinetic analysis of specific cell growth rate (μx) and specific PQQ formation rate (μp), the discrepancy in optimal pH values between cell growth and PQQ biosynthesis was observed, which stimulated us to develop a novel two-stage pH control strategy. During this pH-shifted process, the pH in the broth was controlled at 6.8 to promote the cell growth for the first 48 h and then shifted to 5.8 to enhance the PQQ synthesis until the end of fermentation. By applying this pH-shifted control strategy, the maximum PQQ production was improved to 158.61 mg/L in the benchtop fermenter, about 44.9% higher than that under the most suitable constant pH fermentation. Further fed-batch study showed that PQQ production could be improved from 183.38 to 272.21 mg/L by feeding of methanol at the rate of 11.5 mL/h in this two-stage pH process. Meanwhile, the productivity was also increased from 2.02 to 2.84 mg/L/h. In order to support cell growth during the shifted pH stage, the combined feeding of methanol and yeast extract was carried out, which brought about the highest concentration (353.28 mg/L) and productivity (3.27 mg/L/h) of PQQ. This work has revealed the potential of our developed simple and economical strategy for the large-scale production of PQQ.
authors.affiliation: Key Laboratory of Biomass Chemical Engineering (Ministry of Education), College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China.|Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, People's Republic of China.
authors.forename: Zhenjun
authors.initials: Z
authors.lastname: Si
authors.affiliation: School of Biological and Chemical Engineering, Zhejiang University of Science and Technology, Hangzhou, 310023, People's Republic of China.
authors.forename: David
authors.initials: D
authors.lastname: Machaku
authors.affiliation: School of Biological and Chemical Engineering, Zhejiang University of Science and Technology, Hangzhou, 310023, People's Republic of China. weipeilian@126.com.
authors.forename: Peilian
authors.initials: P
authors.lastname: Wei
authors.affiliation: Key Laboratory of Biomass Chemical Engineering (Ministry of Education), College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China.|Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Huang
authors.affiliation: Key Laboratory of Biomass Chemical Engineering (Ministry of Education), College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China.
authors.forename: Jin
authors.initials: J
authors.lastname: Cai
authors.affiliation: Key Laboratory of Biomass Chemical Engineering (Ministry of Education), College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China. znxu@zju.edu.cn.|Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, People's Republic of China. znxu@zju.edu.cn.
authors.forename: Zhinan
authors.initials: Z
authors.lastname: Xu
mesh_terms: D061249:Batch Cell Culture Techniques / Q000191:economics / Q000379:methods*; D018533:Biomass; D003470:Culture Media / Q000737:chemistry; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D020631:Methylobacillus / Q000254:growth & development* / Q000378:metabolism*; D045542:PQQ Cofactor / Q000096:biosynthesis*
chemical_list: D003470:Culture Media; D045542:PQQ Cofactor; D005947:Glucose
keywords: Fed-batch; Methylobacillus sp. CCTCC M2016079; Pyrroloquinoline quinine (PQQ); Two-stage pH control strategy