A mulfistep conversion system composed of phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） was used to synthesize methylcatechols and semialdehydes from o- and m-cresol for the first time. Docking studies displayed by PyMOL predicted that cresols and methylcatechols could be theoretically transformed by this multistep conversion system~ High performance liquid chromatography mass spectrometry （HPLC-MS） analysis also indicated that the products formed from multistep conversion were the corresponding 3-methylcatechol, 4-methylcatechol, 2- hydroxy-3-methyl-6-oxohexa-2,4-dienoic acid （2- hydroxy-3-methyl-ODA） and 2-hydroxy-5-methyl-6-oxo- hexa-2,4-dienoic acid （2-hydroxy-5-methyl-ODA）. The optimal cell concentrations of the recombinant E. coli strain BL21 （DE3） expressing phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） and pH for the multistep conversion of o- and m-cresol were 4.0 （g-L-1 cell dry weight） and pH 8.0, respectively. For the first step conversion, the formation rate of 3- methylcatechol （0.29μmol·L-1·min-1·mg-1cell dry weight） from o-cresol was similarly with that ofmethylca- techols （0.28 μmol·L-1·min-1·mg-1 cell dry weight） from m-cresol by strain PHrND. For the second step conversion, strain BphCLA_4 showed higher formation rate （0.83 μmol·L-1·min-1·mg-1 cell dry weight） for 2-hydroxy-3-methyl- ODA and 2-hydroxy-5-methyl-ODA from m-cresol, which was 1.1-fold higher than that for 2-hydroxy-3-methyl- ODA （0.77 μmol·L-1·min-1·mg-1. mglcell dry weight） from ocresol. The present study suggested the potential application of the multistep conversion system for the production of chemical synthons and high-value products.
为强化载体表面生物膜的活性,研究以水性聚氨酯(waterborne polyurethane)为介质制备负载电气石的聚氨酯(tourmaline on polyurethane,TPU)载体.用扫描电镜(SEM)和持水倍率表征载体的物理性能,并且考察TPU载体对挂膜量及硝化能力的影响.结果表明,水溶性聚氨酯浓度能够影响TPU载体对电气石的负载量,导入电气石可以优化TPU载体上极性基团的数量以及环境pH值,亚硝酸菌和硝酸菌在TPU载体上的不可逆附着量分别提高了74.82%和71.89%.与未投载体相比,NH4+-N和NO2--N的去除率分别提高了8.12%和9.08%,表明优化的TPU载体能促进硝化作用.
