Purification and studies on characteristics of cholinesterases from Daphnia magna

Due to their significant value in both economy and ecology,Daphnia had long been employed to investigate in vivo response of cholinesterase(ChE) in anticholinesterase exposures,whereas the type constitution and property of the enzyme remained unclear.A type of ChE was purified from Daphnia magna using a three-step procedure,i.e.,Triton X-100 extraction,ammonium sulfate precipitation,and diethylaminoethyl(DEAE)-Sepharose Fast-Flow chromatography.According to sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE),molecular mass of the purified ChE was estimated to be 84 kDa.Based on substrate studies,the purified enzyme preferred butyrylthiocholine iodide(BTCh) [with maximum velocity(Vmax)/Michaelis constant(Km)=8.428 L/(min·mg protein)] to acetylthiocholine iodide(ATCh) [with V max /Km =5.346 L/(min·mg protein)] as its substrate.Activity of the purified enzyme was suppressed by high concentrations of either ATCh or BTCh.Inhibitor studies showed that the purified enzyme was more sensitive towards inhibition by tetraisopropylpyrophosphoramide(iso-OMPA) than by 1,5-bis(4-allyldimethylammoniumphenyl) pentan-3-one dibromide(BW284C51).Result of the study suggested that the purified ChE was more like a type of pseudocholinesterase,and it also suggested that Daphnia magna contained multiple types of ChE in their bodies.

Pore-scale lattice Boltzmann simulation of flow and mass transfer in bioreactor with an immobilized granule for biohydrogen production

The photo bioreaction combined with flow and mass transfer is simulated with pore-scale lattice Boltzmann （LB） method, which is the scenario of a bioreactor filled with a porous granule immobilized photosynthetic bacteria cells for hydrogen production. The quartet structure generation set （QSGS） is used to generate porous structure of the immobilized granule. The effects of porosity of the immobilized granule on flow and concentration fields as well as the hydrogen production performance are investi- gated. Higher porosity facilitates the substrate solution smoothly flowing through the porous granule with increasing velocity, and thus results in higher product concentration inside the immobilized gran- ule. Additionally, the substrate consumption efficiency increases, while hydrogen yield slightly decreases with increasing porosity, and they tend to stable for the porosity larger than 0.5. Furthermore, the LB numerical results have a good agreement with the experimental results. It is demonstrated that the pore-scale LB simulation method coupling with QSGS is available to simulate the photo hydrogen produc- tion in the hioreactor with porous immobilized granules.