BackgroundBiocatalytic production of L‐phosphinothricin (L‐PPT) is currently the most promising method. In this work, we use an Escherichia coli strain coexpressing of D‐amino acid oxidase and catalase (E. coli DAAO‐CAT) to oxidation biocatalytic D‐PPT to PPO, then use the second E. coli strain coexpressing glutamate dehydrogenase and formate dehydrogenase (E. coli GluDH‐FDH) to reduce biocatalytic PPO to L‐PPT.Main Methods and Major ResultsWe compared the effects of different concentrations of IPTG or lactose on protein expression and enzyme activity in 5 L fermenter. The best induction conditions for E. coli DAAO‐CAT were 0.05 mM IPTG, induction for 18 h at 28°C. The specific enzyme activities of DAAO and CAT were 153.20 U g−1 and 896.23 U g−1, respectively. The optimal induction conditions for E. coli GluDH‐FDH were 0.2 mM IPTG, induction for 19 h at 28°C. The specific enzyme activities of GluDH and FDH were 41.72 U g−1 and 109.70 U g−1, respectively. The 200 mM D‐PPT was biocatalyzed by E. coli DAAO‐CAT for 4 h with space‐time yield of 9.0 g·L−1·h−1 and conversion rate of over 99.0%. Then 220 mM PPO was converted to L‐PPT by E. coli GluDH‐FDH for 3 h with space‐time yield of 14.5 g·L−1·h−1 and conversion rate of over 99.0%. To our knowledge, this is the most efficient biocatalytic reaction for L‐PPT production.Conclusions and ImplicationsWe found that IPTG has advantages compared with lactose in the enzyme activity and biomass of E. coli DAAO‐CAT and E. coli GluDH‐FDH, and IPTG is more environmentally friendly. Our data implicated that IPTG can replace lactose in terms of economic feasibility and effectiveness for scaled‐up industrial fermentations.

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d-amino acid oxidase (DAAO) is widely used in the industrial preparation of l-amino acids, and cultivating Escherichia coli (E. coli) expressing DAAO for the biosynthesis of l-phosphinothricin (l-PPT) is very attractive. At present, the biomass production of DAAO by fermentation is still limited in large-scale industrial applications because the expression of DAAO during the fermentation process inhibits the growth of host cells, which limits higher cell density. In this study, the factors that inhibit the growth of bacterial cells during a 5 L fed-batch fermentation process were explored, and the fermentation process was optimized by co-expressing catalase (CAT), by balancing the biomass and the enzyme activity, and by adding exogenous d-alanine (d-Ala) to relieve the limitation of DAAO on the cells and optimize fermentation. Under optimal conditions, the DO-STAT feeding mode with DO controlled at 30% ± 5% and the addition of 27.5 g/L lactose mixed with 2 g/L d-Ala during induction at 28 °C resulted in the production of 26.03 g dry cell weight (DCW)/L biomass and 390.0 U/g DCW speci c activity of DAAO; an increase of 78% and 84%, respectively, compared with the initial fermentation conditions. The fermentation strategy was successfully scale-up to a 5000L fermenter.

Background: National and international experts have been attempting to find diagnostic tools for the early identification of symptoms to facilitate early identification and intervention of the disease. Objective: Detection of urine Alzheimer-associated neuronal thread protein (AD7c-NTP) and serum 25-hydroxyvitamin D (25(OH)D) in the diagnosis of Alzheimer’s disease (AD). Methods: Subjects aged >50 years who underwent a physical examination at the Taihu Sanatorium of Jiangsu Province, had no clinical evidence of AD-related issues, and had normal Mini-Mental State Exam and Montreal Cognitive Assessment scores were enrolled in the present study. There were 35 males and 15 females, who were aged 51–91 years. Urine AD7c-NTP levels and serum 25(OH)D concentrations were measured. Results: The Pearson correlation analysis revealed that the urine AD7c-NTP levels in these subjects were negatively correlated with the serum 25(OH)D concentrations (r = –0.460, p <  0.001). Conclusion: Combined with previous studies, it was considered that cognitive function might be the only link for the correlation between AD7c-NTP and 25(OH)D. This finding might provide a starting point to investigate the potential value of the interaction between urine AD7c-NTP and serum 25(OH)D in chronic diseases. Further large-scale studies are needed to validate the results of the present study.