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Ji Y, Guan F, Zhou X, Liu X, Wu N, Liu D, Tian J. Construction of a mApple-D6A3-mediated biosensor for detection of heavy metal ions. AMB Express 2020; 10:213. [PMID: 33284386 PMCID: PMC7721944 DOI: 10.1186/s13568-020-01154-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 11/27/2020] [Indexed: 11/23/2022] Open
Abstract
Pollution of heavy metals in agricultural environments is a growing problem to the health of the world’s human population. Green, low-cost, and efficient detection methods can help control such pollution. In this study, a protein biosensor, mApple-D6A3, was built from rice-derived Cd2+-binding protein D6A3 fused with the red fluorescent protein mApple at the N-terminus to detect the contents of heavy metals. Fluorescence intensity of mApple fused with D6A3 indicated the biosensor’s sensitivity to metal ions and its intensity was more stable under alkaline conditions. mApple-D6A3 was most sensitive to Cu2+, then Ni2+, then Cd2+. Isothermal titration calorimetry experiments demonstrated that mApple-D6A3 successfully bound to each of these three metal ions, and its ability to bind the ions was, from strongest to weakest, Cu2+ > Cd2+ > Ni2+. There were strong linear relationships between the fluorescence intensity of mApple-D6A3 and concentrations of Cd2+ (0–100 μM), Cu2+ (0–60 μM) and Ni2+ (0–120 μM), and their respective R2 values were 0.994, 0.973 and 0.973. When mApple-D6A3 was applied to detect concentrations of heavy metal ions in water (0–0.1 mM) or culture medium (0–1 mM), its accuracy for detection attained more than 80%. This study demonstrates the potential of this biosensor as a tool for detection of heavy metal ions.
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Hou Y, Gao B, Cui J, Tan Z, Qiao C, Jia S. Combination of multi-enzyme expression fine-tuning and co-substrates addition improves phenyllactic acid production with an Escherichia coli whole-cell biocatalyst. BIORESOURCE TECHNOLOGY 2019; 287:121423. [PMID: 31103936 DOI: 10.1016/j.biortech.2019.121423] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/02/2019] [Accepted: 05/03/2019] [Indexed: 06/09/2023]
Abstract
The aim of this study was to develop an environmentally safe and efficient method for phenyllactic acid (PLA) production using whole-cell cascade catalysis with l-amino acid deaminase (l-AAD), lactate dehydrogenase (LDH), and formate dehydrogenase (FDH). The PPA titer was low due to relatively low expression of LDH, intermediate accumulation, and lack of cofactors. To address this issue, ribosome binding site regulation, gene duplication, and induction optimization were performed to increased the PLA titer to 43.8 g/L. Then co-substrates (glucose, yeast extract, and glycerol) were used to increase NADH concentration and cell stability, resulting that the PLA titer was increased to 54.0 g/L, which is the highest reported production by biocatalyst. Finally, glucose was replaced with wheat straw hydrolysate as co-substrate to decrease the cost. Notably, the strategies reported herein may be generally applicable to other whole-cell cascade biocatalysts.
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Affiliation(s)
- Ying Hou
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Engineering Research Center of Microbial Metabolism and Fermentation Process Control, 300457 Tianjin, China.
| | - Bo Gao
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Engineering Research Center of Microbial Metabolism and Fermentation Process Control, 300457 Tianjin, China
| | - Jiandong Cui
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Engineering Research Center of Microbial Metabolism and Fermentation Process Control, 300457 Tianjin, China
| | - Zhilei Tan
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Engineering Research Center of Microbial Metabolism and Fermentation Process Control, 300457 Tianjin, China
| | - Changsheng Qiao
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Peiyang Biotrans Co., Ltd, Tianjin 300457, China
| | - Shiru Jia
- State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Engineering Research Center of Microbial Metabolism and Fermentation Process Control, 300457 Tianjin, China.
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