Structure Modeling of Azoreductase AZR and Site-directed Mutagenesis of Its K~(109) Residue / 微生物学通报

Three-dimensional structure model of azoreductase AZR of Rhodobacter sphaeroides was con- structed using homology modeling method. It is a flavodoxin adopting ?/? structure. Structure alignment of two different types of flavin-dependent azoreductases revealed that they possessed high similarity. Based on sequence and structure analysis, site-directed mutagenesis of K109H and K109A were performed. The opti- mal pH values are pH 6 and pH 9 for K109H and K109A mutant protein, respectively. The optimal tempera- ture (30℃) is not affected by mutagenesis. Positively charged residues at position 109 is necessary for the binding of methyl red, while K109H is not a conserved mutagenesis for the binding of NADPH. K109 may only be involved in the binding of the 2’-phosphate group of NADPH and have no effect on the binding of NADH.

BIOLOGICAL ASPECTS IN THE MEMBRANE BIOREACTOR / 微生物学通报

For the efficient interception performance of the membrane, some biological aspect in membrane bioreactor are different from those in the activated sludge process. The physiological and biochemical characteristics of microbial community, activated sludge, and microbial products in the membrane bioreactor are illustrated in this paper.