Phenylpyruvic acid (PPA) is used as a food and feed additive and has a wide range of applications in the pharmaceutical, chemical and other fields. At present, PPA is mainly produced by chemical synthesis. With the green transformation of the manufacturing industry, biotransformation will be a good alternative for PPA production. The L-amino acid deaminase (PmiLAAD) from Proteus mirabilis has been widely studied for the production of PPA. However, the low yield limits its industrial production. To further enhance the production of PPA and better meet industrial demands, a more efficient synthesis method for PPA was established. In this study, PmiLAAD was heterologously expressed in Escherichia coli. Subsequently, a colorimetric reaction method was established to screen the strains with high PPA production. The semi-rational design of PmiLAAD was carried out, and the obtained triple-site mutant V18 (V437I/S93C/E417A) showed a 35% increase in catalytic activity compared with the wild type. Meanwhile, the effect of N-terminal truncation on the catalytic activity of the V18 mutant was investigated. After the optimization of the whole-cell conditions for the obtained mutant V18-N7, fed-batch conversion was carried out in a 5-L fermenter, and 44.13 g/L of PPA was synthesized with a conversion rate of 88%, which showed certain potential for industrial application. This study lays foundation for the industrial production of phenylpyruvic acid and also offers insights into the biosynthesis of other chemicals.
Escherichia coli/metabolism* ; Proteus mirabilis/genetics* ; Phenylpyruvic Acids/metabolism* ; Protein Engineering/methods* ; Recombinant Proteins/biosynthesis* ; Bacterial Proteins/metabolism*

γ-aminobutyric acid can be produced by a one-step enzymatic reaction catalyzed by glutamic acid decarboxylase. The reaction system is simple and environmentally friendly. However, the majority of GAD enzymes catalyze the reaction under acidic pH at a relatively narrow range. Thus, inorganic salts are usually needed to maintain the optimal catalytic environment, which adds additional components to the reaction system. In addition, the pH of solution will gradually rise along with the production of γ-aminobutyric acid, which is not conducive for GAD to function continuously. In this study, we cloned the glutamate decarboxylase LpGAD from a Lactobacillus plantarum capable of efficiently producing γ-aminobutyric acid, and rationally engineered the catalytic pH range of LpGAD based on surface charge. A triple point mutant LpGAD^{S24R/D88R/Y309K} was obtained from different combinations of 9 point mutations. The enzyme activity at pH 6.0 was 1.68 times of that of the wild type, suggesting the catalytic pH range of the mutant was widened, and the possible mechanism underpinning this increase was discussed through kinetic simulation. Furthermore, we overexpressed the Lpgad and Lpgad^{S24R/D88R/Y309K} genes in Corynebacterium glutamicum E01 and optimized the transformation conditions. An optimized whole cell transformation process was conducted under 40 ℃, cell mass (OD₆₀₀) 20, 100 g/L l-glutamic acid substrate and 100 μmol/L pyridoxal 5-phosphate. The γ-aminobutyric acid titer of the recombinant strain reached 402.8 g/L in a fed-batch reaction carried out in a 5 L fermenter without adjusting pH, which was 1.63 times higher than that of the control. This study expanded the catalytic pH range of and increased the enzyme activity of LpGAD. The improved production efficiency of γ-aminobutyric acid may facilitate its large-scale production.
Glutamate Decarboxylase/genetics* ; Lactobacillus plantarum/genetics* ; Catalysis ; gamma-Aminobutyric Acid ; Hydrogen-Ion Concentration ; Glutamic Acid

L-glutamic acid is the world's largest bulk amino acid product that is widely used in the food, pharmaceutical and chemical industries. Using Corynebacterium glutamicum G01 as the starting strain, the fermentation by-product alanine content was firstly reduced by knocking out the gene encoding alanine aminotransferase (alaT), a major by-product related to alanine synthesis. Secondly, since the α-ketoglutarate node carbon flow plays an important role in glutamate synthesis, the ribosome-binding site (RBS) sequence optimization was used to reduce the activity of α-ketoglutarate dehydrogenase and enhance the glutamate anabolic flow. The endogenous conversion of α-ketoglutarate to glutamate was also enhanced by screening different glutamate dehydrogenase. Subsequently, the glutamate transporter was rationally desgined to improve the glutamate efflux capacity. Finally, the fermentation conditions of the strain constructed using the above strategy were optimized in 5 L fermenters by a gradient temperature increase combined with a batch replenishment strategy. The glutamic acid production reached (135.33±4.68) g/L, which was 41.2% higher than that of the original strain (96.53±2.32) g/L. The yield was 55.8%, which was 11.6% higher than that of the original strain (44.2%). The combined strategy improved the titer and the yield of glutamic acid, which provides a reference for the metabolic modification of glutamic acid producing strains.
Glutamic Acid ; Corynebacterium glutamicum/genetics* ; Ketoglutaric Acids ; Metabolic Engineering ; Alanine

Osteoporotic thoracolumbar fracture in the elderly will seriously reduce their quality of life and life expectancy. For osteoporotic thoracolumbar fracture in the elderly, spinal reconstruction is necessary, which should comprehensively consider factors such as the physical condition, fracture type, clinical characteristics and osteoporosis degree. While there lacks relevant clinical norms or guidelines on selection of spinal reconstruction strategies. In order to standardize the concept of spinal reconstruction for osteoporotic thoracolumbar fracture in the elderly, based on the principles of scientificity, practicality and progressiveness, the authors formulated the Clinical guideline for spinal reconstruction of osteoporotic thoracolumbar fracture in elderly patients ( version 2022), in which suggestions based on evidence of evidence-based medicine were put forward upon 10 important issues related to the fracture classification, non-operative treatment strategies and surgical treatment strategies in spinal reconstruction after osteoporosis thoracolumbar fracture in the elderly, hoping to provide a reference for clinical treatment.

Chest trauma is one of the most common injuries. Venous thromboembolism (VTE) as a common complication of chest trauma seriously affects the quality of patients′ life and even leads to death. Although there are some consensus and guidelines on the prevention and treatment of VTE at home and abroad, the current literatures lack specificity considering the diagnosis, treatment and prevention of VTE in patients with chest trauma have their own characteristics, especially for those with blunt trauma. Accordingly, China Chest Injury Research Society and editorial board of Chinese Journal of Traumatology organized relevant domestic experts to jointly formulate the Chinese expert consensus on the diagnosis, treatment and prevention of chest trauma venous thromboembolism associated with chest trauma (2022 version). This consensus provides expert recommendations of different levels as academic guidance in terms of the characteristics, clinical manifestations, risk assessment, diagnosis, treatment, and prevention of chest trauma-related VTE, so as to offer a reference for clinical application.

Adenocarcinoma of esophagogastric junction (AEG) has attracted more attention in recent years. Surgical method of Siewert type Ⅱ AEG is especially controversial, mainly focusing on the scope of lymph node dissection, safety of surgical margin, and digestive tract reconstruction. The abdominal transhiatal approach and right thoracoabdominal Ivor-Lewis approach are the main surgical approaches of totally laparoscopic or thoracoscopic surgery for Siewert type Ⅱ AEG, which not only need close teamwork, but also require rich experience in laparoscopic surgery. The authors has started to choose these two totally minimally invasive surgical approaches, the feasibility and safety of which are proved. The key surgical details are presented in this article for reference.

Glutamic acid is an important amino acid with wide range of applications and huge market demand. Therefore, by performing transcriptome sequencing and re-sequencing analysis on Corynebacterium glutamicum E01 and high glutamate-producing strain C. glutamicum G01, we identified and selected genes with significant differences in transcription and gene levels in the central metabolic pathway that may have greatly influenced glutamate synthesis and further increased glutamic acid yield. The oxaloacetate node and α-ketoglutarate node play an important role in glutamate synthesis. The oxaloacetate node and α-ketoglutarate node were studied to explore effect on glutamate production. Based on the integrated strain constructed from the above experimental results, the growth rate in a 5-L fermenter was slightly lower than that of the original strain, but the glutamic acid yield after 48 h reached (136.1±5.53) g/L, higher than the original strain (93.53±4.52) g/L, an increase by 45.5%; sugar-acid conversion rate reached 58.9%, an increase of 13.7% compared to 45.2% of the original strain. The application of the above experimental strategy improved the glutamic acid yield and the sugar-acid conversion rate, and provided a theoretical basis for the metabolic engineering of Corynebacterium glutamicum.
Citric Acid Cycle ; Corynebacterium glutamicum/metabolism* ; Glutamic Acid/metabolism* ; Metabolic Engineering ; Metabolic Networks and Pathways/genetics*

Intraoperative hemorrhage is the most common complication of laparoscopic radical gastrectomy,which is also the main cause of conversion to open surgery.With the popularization of laparoscopic surgery technology worldwide,how to complete high-quality surgery and effectively avoid intraoperative or postoperative complications is the goal pursued by all surgeons.Intraoperative hemorrhage in the laparoscopic radical gastrectomy is mainly divided into parenchymal hemorrhage,perigastric vascular injury-induced hemorrhage,lymph node hemorrhage and anastomotic bleeding.Compression,electrocoagulation,vascular clipping and vascular suture repair are the most common treatments for intraoperative hemorrhage.It is necessary to use above methods in clinical work.Proficiency in laparoscopic operation skills,familiarity with perigastric vascular anatomy and variation,and improved teamwork to reduce complications are the key to laparoscopic surgery for gastric cancer.Combined with literature reports,the authors summarize experience in laparoscopic surgery for gastric cancer,discuss the prevention and treatment of hemorrhagic complications during laparoscopic radical gastrectomy.

Objective To research the clinical application value of laparoscopic bile duct exploration and the first stage suture for choledocholithiasis. Methods The clinical data of 86 patients with choledocholithiasis were analyzed retrospectively from January 2015 to January 2017 in Affiliated Suzhou Hospital of Nanjing Medical University. According to the different methods of laparoscopic bile duct exploration, they were divided into one stage suture group (observation group, 46 cases) and T tube drainage group (control group, 40 cases). Results The recovery time of gastrointestinal function, hospitalization time and hospitalization expenses in observation group were significantly better than those in control group: (22.71 ± 10.92) h vs. (35.63 ± 11.12) h, (8.4 ± 2.6) d vs. (13.5 ± 2.3) d and (12.1 ± 3.2) thousand yuan vs. (13.5 ± 4.2) thousand yuan, and there were statistical differences (P＜0.05). Conclusions Compared with T tube drainage, the first stage suture after laparoscopic common bile duct exploration has shorter hospitalization time, lower treatment cost and faster recovery. It is a safe and feasible operation method, and is worthy of popularization and application.