In this study, Escherichia coli BL21 (DE3) was used as the host to construct 2 recombinant E. coli strains that co-expressed leucine dehydrogenase (LDH, Bacillus cereus)/formate dehydrogenase (FDH, Ancylobacter aquaticus), or leucine dehydrogenase (LDH, Bacillus cereus)/alcohol dehydrogenase (ADH, Rhodococcus), respectively. L-2-aminobutyric acid was then synthesized by L-threonine deaminase (L-TD) with LDH-FDH or LDH-ADH by coupling with two different NADH regeneration systems. LDH-FDH process and LDH-ADH process were optimized and compared with each other. The optimum reaction pH of LDH-FDH process was 7.5, and the optimum reaction temperature was 35 °C. After 28 h, the concentration of L-2-aminobutyric acid was 161.8 g/L with a yield of 97%, when adding L-threonine in batches for controlling 2-ketobutyric acid concentration less than 15 g/L and using 50 g/L ammonium formate, 0.3 g/L NAD+, 10% LDH-FDH crude enzyme solution (V/V) and 7 500 U/L L-TD. The optimum reaction pH of LDH-ADH process was 8.0, and the optimum reaction temperature was 35 °C. After 24 h, the concentration of L-2-aminobutyric acid was 119.6 g/L with a yield of 98%, when adding L-threonine and isopropanol (1.2 times of L-threonine) in batches for controlling 2-ketobutyric acid concentration less than 15 g/L, removing acetone in time and using 0.3 g/L NAD⁺, 10% LDH-ADH crude enzyme solution (V/V) and 7 500 U/L L-TD. The process and results used in this paper provide a reference for the industrialization of L-2-aminobutyric acid.
Aminobutyrates ; metabolism ; Escherichia coli ; genetics ; Formate Dehydrogenases ; metabolism ; Leucine Dehydrogenase ; metabolism ; NAD ; metabolism

With the improvement of modern surgical techniques and surgical instruments,combined with mutiple artery-first approaches in pancrcaticoduodenectomy,can shorten the operation time effectively,reduce intraoperative blood loss,regulate lymph node dissection,improve R0 resection rate,and thus improve the prognosis of patients,has become an important surgical treatment of pancreatic cancer and periampullary cancer.The principle of the proposed basis is mainly based on "anatomical basis no-touch concept" and " pancreatic mesorectal excision" and the combination of the main approches:superior approach,posterior approach,interior approach (anterior approach,medial uncinate approach,mesentery approach).Pancreatic surgeons need to judge the position of the tumor and the intraoperative situation,weigh the benefits and disadvantages of each approach,so as to combine theory with practice,flexibility with principle.

With the widespread implementation of laparoscopic cholecystectomy in various levels of medical institutions, surgical complications have also increased. Among them, the incidence of bile duct injury remains high in complex laparoscopic cholecystectomy. The reason for this is that surgeons cannot effectively and accurately identify the relationship between the aberrant bile duct and the cystic duct and the common bile duct, resulting in the accidental injury of the bile duct, resulting in long hospital stays, increased medical costs, and decreased long-term quality of life for patients. Intraoperative cholangiography, as a real-time visual method of biliary presentation, can effectively reduce the incidence of iatrogenic bile duct injury. However, most surgeons do not fully understand the technology of intraoperative cholangiography during cholecystectomy. This article reviews the application of intraoperative cholangiography in laparoscopic cholecystectomy based on the clinical experience of the author′s team and the literature in recent years, with the aim of deepening the understanding of surgeons about intraoperative cholangiography, so as to better apply it to clinical practice and benefit patients.

Objective: To explore the related factors of negative conversion time (NCT) of nucleic acid in children with COVID-19. Methods: A retrospective cohort study was conducted. A total of 225 children who were diagnosed with COVID-19 and admitted to Changxing Branch of Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine from April 3^rd to May 31^st 2022 were enrolled in the study. The infection age, gender, viral load, basic disease, clinical symptoms and information of accompanying caregivers were retrospectively analyzed. According to age, the children were divided into<3 years of age group and 3-<18 years of age group. According to the viral nucleic acid test results, the children were divided into positive accompanying caregiver group and negative accompanying caregiver group. Comparisons between groups were performed using Mann-Whitney U test or Chi-square test. Multivariate Logistic regression analysis was used to analyze the related factors of NCT of nucleic acid in children with COVID-19. Results: Among the 225 patients (120 boys and 105 girls) of age 2.8 (1.3, 6.2) years, 119 children <3 years and 106 children 3-<18 years of age, 19 cases were diagnosed with moderate COVID-19, and the other 206 cases were diagnosed with mild COVID-19. There were 141 patients in the positive accompanying caregiver group and 84 patients in the negative accompanying caregiver group.Patients 3-<18 years of age had a shorter NCT (5 (3, 7) vs.7 (4, 9) d, Z=-4.17, P<0.001) compared with patients <3 years of age. Patients in the negative accompanying caregiver group had a shorter NCT (5 (3, 7) vs.6 (4, 9) d,Z=-2.89,P=0.004) compared with patients in the positive accompanying caregiver group. Multivariate Logistic regression analysis showed that anorexia was associated with NCT of nucleic acid (OR=3.74,95%CI 1.69-8.31, P=0.001). Conclusion: Accompanying caregiver with positive nucleic acid test may prolong NCT of nucleic acid, and decreased appetite may be associated with prolonged NCT of nucleic acid in children with COVID-19.
Adolescent ; Child ; Child, Preschool ; Female ; Humans ; Male ; Young Adult ; China/epidemiology* ; COVID-19/genetics* ; Nucleic Acids ; Retrospective Studies