Enhanced production of bacitracin via energy metabolism engineering in Bacillus licheniformis DW2 / 生物工程学报

Bacitracin is a broad-spectrum cyclic peptide antibiotic, and mainly produced by Bacillus. Energy metabolism plays as a critical role in high-level production of target metabolites. In this study, Bacillus licheniformis DW2, an industrial strain for bacitracin production, was served as the original strain. First, our results confirmed that elimination of cytochrome bd oxidase branch via deleting gene cydB benefited bacitracin synthesis. Bacitracin titer and ATP content were increased by 10.97% and 22.96%, compared with those of original strain, respectively. Then, strengthening cytochrome aa3 oxidase branch via overexpressing gene qoxA was conducive to bacitracin production. Bacitracin titer and ATP content were increased by 18.97% and 34.00%, respectively. In addition, strengthening ADP synthesis supply is also proven as an effective strategy to promote intracellular ATP accumulation, overexpression of adenosine kinase DcK and adenylate kinase AdK could all improve bacitracin titers, among which, dck overexpression strain showed the better performance, and bacitracin titer was increased by 16.78%. Based on the above individual methods, a method of combining the deletion of gene cydB and overexpression of genes qoxA, dck were used to enhance ATP content of cells to 39.54 nmol/L, increased by 49.32% compared to original strain, and bacitracin titer produced by the final strain DW2-CQD (DW2ΔcydB::qoxA::dck) was 954.25 U/mL, increased by 21.66%. The bacitracin titer produced per cell was 2.11 U/CFU, increased by 11.05%. Collectively, this study demonstrates that improving ATP content was an efficient strategy to improve bacitracin production, and a promising strain B. licheniformis DW2-CQD was attained for industrial production of bacitracin.

Clinical feature of and therapeutic effect of emergency peritoneal dialysis in the hospitalized elderly patients with ARF / 中国实用内科杂志

Objective To investigate the common causes of acute renal failure(ARF) in the elderly hospitalized patients and the effect of continuous peritoneal dialysis(PD) by bedside intubation.Methods The data of hospitalized patients with ARF including 28 elderly patients (mean age 68.2?9.6 yrs) and 13 adult patients (mean age 39.4?9.1 yrs) were studied.Of them,32 patients received PD by bedside intubation.The nosogenesis of ARF was analyzed and the effect of emergency PD by bedside cmpared between two groups.Results Among various causes,prerenal factors accounted for 32.1%,infection and wound of bad control 39.3%,unreasonable use of nephrotoxic drugs 14.3%,which totally accounted for 85.7%.Of 21 elderly patients (76%) receiving PD treatment,11 (52.4%) acquired completely remission,5 (23.8%) turned to chronic PD,the successful rate of intensive care being 81.0%,and the death rate being 19.1%.Conclusion Prerenal factors,infection,wound of bad and unreasonable use of nephrotoxic drugs are the common causes of ARF in the elderly hospitalized patients.PD by bedside intubation is safe,simple and effective.