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Objective: To evaluate whether patients with malignant biliary obstruction (MBO) benefit from balloon dilation before the placement of a self‐expanding metal stent (SEMS) for palliative biliary drainage. Methods: Consecutive patients who underwent endoscopic retrograde cholangiopancreatography with SEMS placement for palliative management of MBO were retrospectively included. Comparative analyses of serum bilirubin levels, post‐procedural adverse events, stent patency time, stent dysfunction, and patient survival were performed between the dilation and non‐dilation groups. Results: A total of 221 patients underwent palliative endoscopic SEMS implantation for MBO from January 2014 to June 2018. Dilation significantly improved the percentage of serum bilirubin improvement (37.0% vs 14.3%, P = 0.001), with a decreasing trend in the incidence of post‐procedural cholangitis (2.5% vs 7.8%, P = 0.075), while the rates of other complications such as pancreatitis and bleeding were not increased. The patency time of SEMS and patient survival did not significantly differ between patients with and without dilation. Patients had endoscopic nasobiliary drainage (ENBD) but not dilation showed similar short‐term outcomes as patients underwent dilation but without ENBD. Conclusions: Dilation with a small‐caliber balloon catheter before the placement of SEMS is a safe and effective approach for MBO. Balloon dilation may improve the short‐term efficacy of SEMS placement, while long‐term outcomes are not obviously affected. The short‐term effect of stricture dilation may be achieved by ENBD. Further studies are needed to confirm our results. [ABSTRACT FROM AUTHOR]

ABSTRACT L-methionine has attracted a great deal of attention for its nutritional, pharmaceutical, and clinical applications. In this study, Escherichia coli W3110 was engineered via deletion of a negative transcriptional regulator MetJ and over-expression of homoserine O-succinyltransferase MetA together with efflux transporter YjeH, resulting in L-methionine overproduction which is up to 413.16 mg/L. The partial inactivation of the L-methionine import system MetD via disruption of metI made the engineered E. coli Δ metJ Δ metI/pTrcA*H more tolerant to high L-ethionine concentration and accumulated L-methionine to a level 43.65% higher than that of E. coli W3110 Δ metJ/pTrcA*H. Furthermore, deletion of lysA, which blocks the lysine biosynthesis pathway, led to a further 8.5-fold increase in L-methionine titer of E. coli Δ metJ Δ metI Δ lysA/pTrcA*H. Finally, addition of Na2S2O3 to the media led to an increase of fermentation titer of 11.45%. After optimization, constructed E. coli Δ metJ Δ metI Δ lysA/pTrcA*H was able to produce 9.75 g/L L-methionine with productivity of 0.20 g/L/h in a 5 L bioreactor. This novel metabolically tailored strain of E. coli provides an efficient platform for microbial production of L-methionine. Biotechnol. Bioeng. 2017;114: 843-851. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

( S)-4-Chloro-3-hydroxybutyronitrile [( S)-CHBN] was used as a chiral building block for the preparation of atorvastatin. In this study, ( R, S)-epichlorohydrin [( R, S)-ECH] and 1,3-dichloro-2-propanol (1,3-DCP) were investigated to prepare ( S)-CHBN by using the halohydrin dehalogenase HheC from Agrobacterium radiobacter AD1. Preparing ( S)-CHBN from ( R, S)-ECH gave a modest enantiomeric excess ( ee), whereas by using 1,3-DCP as the substrate, ( S)-CHBN was obtained with 97.3 % ee after pH optimization. However, a low ee value and low yield of ( S)-CHBN were obtained if the substrate concentration was increased to 10 g L−1. To obtain a higher ee value and yield, 16 mutants were constructed and screened. The variant W249F with improvements in activity and enantioselectivity was identified and applied at a 1,3-DCP loading of 10 g L−1, which gave ( S)-CHBN in 86 % yield with 97.5 % ee in 1 h. This is the first report of a one-step biocatalytic process for the preparation of ( S)-CHBN from prochiral 1,3-DCP. [ABSTRACT FROM AUTHOR]