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Mupirocin, a polyketide antibiotic produced by Pseudomonas fluorescens, is used as a topical antimicrobial treatment to cure various skin infections. Quorum sensing system plays an important role in regulation of mupirocin biosynthesis in P. fluorescens NCIMB 10586. In Pseudomonas, the RpeA/RpeB two-component signal transduction (TCST) system regulates quorum sensing system. However, the influences of the RpeA/RpeB TCST system on mupirocin production or other cell activities have not been studied. In this work, the homologous genes of rpeA and rpeB in P. fluorescens NCIMB 10586 were identified and inactivated in the chromosome, respectively. The deletion of rpeA reduced the mupirocin production from 160 in the wild-type to 21.3 mg/L along with slightly decreased cell growth, while no significant effected on mupirocin production in the rpeB mutant. Next, it was found that the RpeA/RpeB TCST system regulated the biosynthesis of mupirocin by modulating the quorum sensing system. Furthermore, untargeted metabolomics analysis was employed to detect the influences of RpeA on other cell activities modulated by quorum sensing system. Combined with quantitative real-time PCR, the results demonstrated that RpeA also regulated other cell activities including central carbon, amino acids, fatty acids, and purine metabolism. Overall, this study expands the current understanding of the RpeA/RpeB TCST system and provides several targets for increasing yields of mupirocin. Key points: • In P. fluorescens, the RpeA/RpeB TCST system regulates the biosynthesis of mupirocin. • RpeA modulates the cell activities through effecting the central carbon metabolism. [ABSTRACT FROM AUTHOR]

Glycerol is a by-product of biodiesel, and it has a great application prospect to be transformed to synthesize high value-added compounds. Pseudomonas chlororaphis GP72 isolated from the green pepper rhizosphere is a plant growth promoting rhizobacteria that can utilize amount of glycerol to synthesize phenazine-1-carboxylic acid (PCA). PCA has been commercially registered as "Shenqinmycin" in China due to its characteristics of preventing pepper blight and rice sheath blight. The aim of this study was to engineer glycerol utilization pathway in P. chlororaphis GP72. First, the two genes glpF and glpK from the glycerol metabolism pathway were overexpressed in GP72ANO separately. Then, the two genes were co-expressed in GP72ANO, improving PCA production from 729.4 mg/L to 993.4 mg/L at 36 h. Moreover, the shunt pathway was blocked to enhance glycerol utilization, resulting in 1493.3 mg/L PCA production. Additionally, we confirmed the inhibition of glpR on glycerol metabolism pathway in P. chlororaphis GP72. This study provides a good example for improving the utilization of glycerol to synthesize high value-added compounds in Pseudomonas. [ABSTRACT FROM AUTHOR]

The static and kinetic adsorption characteristics of Streamline DEAE and DEAE-Sepharose FF were studied under various operating conditions. The adsorption isotherms for the two types of adsorbents were obtained and found to fit well to a Langmuir-type expression. The adsorption kinetics of Streamline DEAE at different concentrations, temperatures, and viscosities were studied and a mathematical model including particle size distribution was developed to describe the adsorption performance of Streamline DEAE. Comparing the uptake curves of Streamline DEAE with DEAE-Sepharose FF, it could be concluded that Streamline DEAE achieves equilibrium faster to get equilibrium than DEAE-Sepharose FF, indicating that Streamline DEAE could be used in higher flow rate systems. [ABSTRACT FROM AUTHOR]

Nattokinase was purified from unclarified Bacillus subtilis culture filtrate using an expanded bed with a purification factor of 8.2 and at a yield of 95%. The optimal pHs for adsorption and elution were 6.0 and 7.0, respectively. The expanded bed route shortened the process time by 8–10 h and increased the yield by 50% when compared with the conventional method. [ABSTRACT FROM AUTHOR]