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SummaryExtracellular fi brinolytic enzyme from Rhizopus microsporus var. tuberosus was purifi ed and characterised. The microorganism was isolated in a distillery from daqu, a fermentative agent used in the production of Chinese liquor and vinegar at diff erent temperatures. The fi brinolytic enzyme was partially purifi ed by ammonium sulphate precipitation, dialysis, DEAE Sepharose ® Fast Flow ion exchange chromatography and Sephadex G-75 gel filtration chromatography. The molecular mass of the fi brinolytic enzyme was estimated to be 24.5 kDa by SDS-PAGE. The purifi ed enzyme showed optimal activity at pH=7.0 and 37 °C by fi brin plate method. It showed stronger resistance to the inhibition by trypsin and was stable at 37 °C retaining 96.1 % residual activity aft er 4 h of incubation. The fi brinolytic activity of the enzyme was enhanced by Na + , Ca 2+ , Mg 2+ and Mn 2+ . Conversely, Zn 2+ and Cu 2+ partly inhibited enzymatic activity. Using fi brin plate method, we found that the enzyme not only degrades fi brin directly, but also activates plasminogen into plasmin to degrade fi brin. The results indicate that the pure enzyme has a potential in dissolving blood clot, and the possibility for application in the treatment of thrombosis.

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This work presents an experimental study to investigate the influence of step volute tongue on aerodynamic performance and aeroacoustic behavior of a forward-curved fan. The noise characteristics are analyzed and controlled based on measured acoustic pressures for various stepped tongues; meanwhile, fan performance is detected and optimized. The design parameters of the stepped tongues are presented to provide significant physical insight into increasing the static pressure as well as the efficiency of static pressure and reducing the fan noise generation. The comparison of the test results indicates that the improved static pressure and its efficiency of the HLHL model have increased by 15.67 Pa and 3.57%, respectively, by comparing with those of the baseline model. At 740 m3/h, a great correlation between different arrays of stepped tongue and the noise generation was observed. The tonal noise level of the HLHL model is a better optimization scheme because it decreases as much as 1.2 dB for the noise generation of forward-curved fan. In particular, it is found that some stepped tongues of the volute tongue achieved the goal of reducing noise generation and improving the performance of fan by experimental measurement at the same time.