Regulation of intracellular level of ATP and NADH in Escherichia coli to promote succinic acid production / 生物工程学报

Succinic acid is an important C4 platform chemical that is widely used in food, chemical, medicine sectors. The bottleneck of fermentative production of succinic acid by engineered Escherichia coli is the imbalance of intracellular cofactors, which often leads to accumulation of by-products, lower yield and low productivity. Stoichiometric analysis indicated that an efficient production of succinic acid by E. coli FMME-N-26 under micro-aeration conditions might be achieved when the TCA cycle provides enough ATP and NADH for the r-TCA pathway. In order to promote succinic acid production, a serial of metabolic engineering strategies include reducing ATP consumption, strengthening ATP synthesis, blocking NADH competitive pathway and constructing NADH complementary pathway were developed. As result, an engineered E. coli FW-17 capable of producing 139.52 g/L succinic acid and 1.40 g/L acetic acid in 5 L fermenter, which were 17.81% higher and 67.59% lower than that of the control strain, was developed. Further scale-up experiments were carried out in a 1 000 L fermenter, and the titer of succinic acid and acetic acid were 140.2 g/L and 1.38 g/L, respectively.

Advances in enzymatic production of L-homophenylalanine / 生物工程学报

L-homophenylalanine (L-HPA) is an important non-natural amino acid that has been used as a key intermediate for the synthesis of Puli drugs for the treatment of hypertension. At present, L-HPA is synthesized using chemical methods, which has the disadvantages of expensive raw materials, tedious steps and serious pollution. Therefore, researchers have conducted in-depth research on the enzymatic production of L-HPA. This review summarizes the research progress on the enzymatic synthesis of L-HPA, including the dehydrogenase process, the transaminase process, the hydantoinase process, and the decarboxylase process, with the hope to facilitate the industrial production of L-HPA.

Metabolic engineering of Escherichia coli for adipic acid production / 生物工程学报

Adipic acid is a high-value-added dicarboxylic acid which is primarily used in the production of nylon-66 for manufacturing polyurethane foam and polyester resins. At present, the biosynthesis of adipic acid is hampered by its low production efficiency. By introducing the key enzymes of adipic acid reverse degradation pathway into a succinic acid overproducing strain Escherichia coli FMME N-2, an engineered E. coli JL00 capable of producing 0.34 g/L adipic acid was constructed. Subsequently, the expression level of the rate-limiting enzyme was optimized and the adipic acid titer in shake-flask fermentation increased to 0.87 g/L. Moreover, the supply of precursors was balanced by a combinatorial strategy consisting of deletion of sucD, over-expression of acs, and mutation of lpd, and the adipic acid titer of the resulting E. coli JL12 increased to 1.51 g/L. Finally, the fermentation process was optimized in a 5 L fermenter. After 72 h fed-batch fermentation, adipic acid titer reached 22.3 g/L with a yield of 0.25 g/g and a productivity of 0.31 g/(L·h). This work may serve as a technical reference for the biosynthesis of various dicarboxylic acids.

Modular engineering of Escherichia coli for high-level production of l-tryptophan / 生物工程学报

As an essential amino acid, l-tryptophan is widely used in food, feed and medicine sectors. Nowadays, microbial l-tryptophan production suffers from low productivity and yield. Here we construct a chassis E. coli TRP3 producing 11.80 g/L l-tryptophan, which was generated by knocking out the l-tryptophan operon repressor protein (trpR) and the l-tryptophan attenuator (trpL), and introducing the feedback-resistant mutant aroGfbr. On this basis, the l-tryptophan biosynthesis pathway was divided into three modules, including the central metabolic pathway module, the shikimic acid pathway to chorismate module and the chorismate to tryptophan module. Then we used promoter engineering approach to balance the three modules and obtained an engineered E. coli TRP9. After fed-batch cultures in a 5 L fermentor, tryptophan titer reached to 36.08 g/L, with a yield of 18.55%, which reached 81.7% of the maximum theoretical yield. The tryptophan producing strain with high yield laid a good foundation for large-scale production of tryptophan.

Prognosis and therapy of patient with renal cell carcinoma accompanied with venous tumor thrombus / 中国综合临床

Objective To investigate the clinical features and prognosis of the patients with renal cell carcinoma and venous tumor thrombus.Methods Fifty-six patients with renal cell carcinoma and venous tumor thrombus were selected as our subjects,who underwent radical nephrectomy and thrombectomy in the Second Hospital of Tianjin Medical University from June 2002 to May 2014.There were 28 patients with stage Ⅰ tumor thrombus,l5with stage Ⅱtumor thrombus,9 with stage Ⅲ tumor thrombus and 4 with stage Ⅳtumor thrombus.All patients underwent renal tumor resection and embolectomy,and were follow-up.Results Of all the patients,46 were male and 10 were female with a mean age of 61.7(age ranging from 42 to 83).Twenty-four were presented on the left kidney and 32 were right.The clinical features were as follows:The tumor size was 2.5 to 14 cm in diameter(mean:6.2 cm),there were 21 cases with low back pain,18 cases with hematuria,lcases with abdominal.Pathological results showed that 39 with clear cell carcinoma,9 with papillary cell carcinoma,3 with chromophobe cell carcinoma,1 with low-differentiated cell carcinoma and 1 with undifferentiated cell carcinoma,3 with sarcomatoid differentiation.Forty-three patients were followed up,and the median follow up period was 20.4 months (2-90 months).The median survival time for the patients was 47 months and the 5 year overall survival was 45.2％.The survival time of the patients with early tumor thrombus(below hepaticvein) was (55.3 ± 4.9) month,significantly longer than that of the patients with advanced tumor thrombus (above hepaticvein) ((24.8 ± 5.3) months,P =0.047).Conclusion Patients with renal cell carcinoma and venous tumor thrombus are characterized with high malignancy and poor prognosis.Surgical operations are effective therapies for the patients.Long term outcome of the early tumor thrombus patients is significantly better than that of the advanced tumor.

Clinical features and CT appearances of primary adenosquamous carcinoma of the liver / 实用放射学杂志

Objective To investigate the clinical features and CT appearances of primary adenosquamous carcinoma (ASC)of the liver and to improve the understanding of this disease for the sake of misdiagnosis.Methods The clinical features and CT appearances in 7 patients proved by operation and pathology were reviewed,retrospectively.Results All of the patients had dull pain in upper abdo-men,fever,chills and a long history of cholangitis and biliary calculi.In addition,all patients had not the history of hepatitis B and liver cirrhosis.And the serum AFP level was normal.The single lesion was found in every patient including 4 lesions in the left lobe of liver and the other 3 in the right lobe.Plain CT showed all masses with hypodensity,heterogeneity and unclear edge in liver,and multiple irregular and more hypodense areas in lesions were found.Slight heterogeneous honeycomb-like enhancement in the arterial phase was showed.In the venous phase,persistent honeycomb-like enhancement with uneven separations,nodular bulge and hypo-dense necrotic area was found.In the delayed phase,further honeycomb-like enhancement with hypodense necrotic area and obvious-ly enhanced nodular bulge was showed.The bile ducts in the liver and around the mass were dilated and had pneumatosis in company with lithiasis in choledochus and intrahepatic bile duct in 5 patients.Conclusion Primary hepatic ASC has certain clinical character-istics in older patients.The CT characteristic features included:honeycomb-like lesions with persistent,heterogeneous,delayed en-hancement and heterogeneous separation,uneven inner edge and enhanced nodular bulge.