Improving the production of 4-aminobenzoic in engineered Escherichia coli by combinatorial regulation / 生物工程学报

Para-aminobenzoate (PABA) is an important chemical for organic synthesis and extensively used in pharmaceutical and dye industry. In recent years, PABA has received increasing attention as a potential component of high-strength polymer. In Escherichia coli, three genes of pabA, pabB and pabC are responsible for PABA production from chorismate in folate synthetic pathway. However, E. coli does not accumulate or accumulates very few amounts of PABA under normal growth condition. In this study, the tyrosine-producing E. coli TYR002 constructed previously was used as the starting strain for developing PABA-producing strain. First, the activity of bifunctional chorismate mutase/prephenate dehydrogenase TyrA in E. coli TYR002 was weakened to reduce the production of tyrosine. Then, three different constitutive promoters were used to regulate the expression of pabA, pabB and pabC in recombinant plasmid which was transformed into E. coli for improving PABA production. The shake-flask fermentation showed that the different combination of constitutive promoters significantly affected the production of PABA, and the highest shake-flask fermentation titer was 0.67 g/L. After further condition optimization, the engineered E. coli produced 6.4 g/L PABA under 5 L fed-batch fermentation. This study could be a good reference for improving microbial production of PABA.

Risk of bloodstream infection in relation with peripherally inserted central venous catheter in hospitalized patients / 中华老年心脑血管病杂志

Objective To study the risk of bloodstream infection in relation with peripherally inserted central venous catheter (PICC) in hospitalized non-cancer patients.Methods Clinical data of 172 non-cancer patients admitted to our hospital for PICC were collected.The risk of PICC-related bloodstream infection (CRBSI) in domestic hospitalized non-cancer patients was analyzed and systematically assessed.Results Of the 183 PICCs placed in 172 patients included in this study,61.7％ were placed in general wards,38.3％ were placed in ICU,87.8％ were placed in combination with indwelling urinary catheter,29.7％ were placed in combination with mechanical ventilation.The median PICC indwelling time was 35 days.CRBSI occurred in 6 patients with an incidence of 0.6/1000 PICCs/day.The risk of CRBSI was centralized in domestic tumor patients after PICC.The reported CRBSI was significantly different in hospitalized non-cancer patients (0.26-33.10/100 PICC).Conclusion The risk of CRBSI is lower in hospitalized patients after PICC placement than after traditional central venous catheter placement.Further studies are needed to assess its value in ICU.