title: Purification and characterization of a serine protease secreted by Brevibacillus sp. KH3 for reducing waste activated sludge and biofilm formation.
abstract: A novel protease secreted by Brevibacillus sp. KH3 isolated from excess sludge at 50 °C and used as a sludge-lysing strain was investigated in this study. Sludge reduction was minimized by protease inhibitors and a 40-kDa protease, which significantly contributed to this sludge-reducing activity, was purified as the target protein. The final purified protease demonstrated 92-fold higher specific activity than the initial crude extracts. The sludge-reducing efficiency deteriorated relative to decreased protease activity triggered by EDTA; thus, the purified protease was a causative agent in reducing excess sludge. The 40-kDa protease was a serine metalloprotease and showed the highest activity at 50 °C and pH 8.0, and the activity was enhanced in the presence of calcium ions, indicating that the purified protease contained calcium ion. Furthermore, this 40-kDa protease inhibited biofilm formation in excess sludge. These results imply that sludge reduction is because of reduction of biofilm formation in excess sludge.
authors.affiliation: Department of Biological Functions and Engineering, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan. toshi.maeda@life.kyutech.ac.jp
authors.forename: Toshinari
authors.initials: T
authors.lastname: Maeda
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yoshimura
authors.forename: Rodolfo
authors.initials: R
authors.lastname: García-Contreras
authors.forename: Hiroaki I
authors.initials: HI
authors.lastname: Ogawa
mesh_terms: D000595:Amino Acid Sequence; D001433:Bacteriolysis / Q000187:drug effects; D001673:Biodegradation, Environmental / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D058675:Brevibacillus / Q000201:enzymology* / Q000502:physiology*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007477:Ions; D008670:Metals / Q000494:pharmacology; D008970:Molecular Weight; D011480:Protease Inhibitors / Q000494:pharmacology; D057057:Serine Proteases / Q000302:isolation & purification* / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*; D013696:Temperature
chemical_list: D007477:Ions; D008670:Metals; D011480:Protease Inhibitors; D012722:Sewage; D057057:Serine Proteases