title: Enhancement of proteolytic enzyme activity excreted from Bacillus stearothermophilus for a thermophilic aerobic digestion process.
abstract: Proteolysis is one of the main enzymatic reactions involved in waste activated sludge (WAS) digestion. In this study, proteases excreted from Bacillus stearothermophilus (ATCC 31197) were classified, and an enhancement of protease activity was achieved using economical chemical additives for WAS digestion. Proteases excreted from B. stearothermophilus were classified into two families: serine and metallo-proteases. Various metal ions were investigated as additives which could potentially enhance protease activity. It was observed that Ca2+ and Fe2+ could markedly activate these enzymes. These results were applied to thermophilic aerobic digestion (TAD) of industrial WAS using B. stearothermophilus. The addition of these divalent ions enhanced the degradation performance of the TAD process in terms of reducing the total suspended solids (TSSs), the dissolved organic carbon (DOC) content, and the intracellular and extracellular protein concentrations. The best result, with respect to protein reduction in a digestion experiment, was obtained by the addition of 2 mM Ca2+. Therefore, a proposed TAD process activated by calcium addition can be successfully used for industrial and municipal WAS digestion to the upgrading of TAD process performance.
authors: Department of Chemical Engineering, Sogang Unirersity, Seoul, South Korea.
authors: Young-Kee
authors: YK
authors: Kim
authors: Jin-Hye
authors: JH
authors: Bae
authors: Byung-Keun
authors: BK
authors: Oh
authors: Won Hong
authors: WH
authors: Lee
authors: Jeong-Woo
authors: JW
authors: Choi
mesh_terms: D001709:Biotechnology; D002118:Calcium / Q000737:chemistry / Q000494:pharmacology; D002412:Cations; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007477:Ions; D007501:Iron / Q000494:pharmacology; D008666:Metalloendopeptidases / Q000737:chemistry; D015233:Models, Statistical; D012697:Serine Endopeptidases / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D015032:Zinc / Q000494:pharmacology
chemical_list: D002412:Cations; D007477:Ions; D007501:Iron; D012697:Serine Endopeptidases; D008666:Metalloendopeptidases; D015032:Zinc; D002118:Calcium