title: Thermostability of selected enzymes in organic wastes and in their humic extract.
abstract: The objective of this study was to evaluate the thermostability up to 70 degrees C for 1 h of selected enzymes present in fresh and composted sewage sludge (SS and SSC) or municipal solid wastes (MSW and MSWC) and their humic extract. After a thermal treatment at 70 degrees C, no beta-glucosidase activity in any humic extract was detected, whereas in SS, SSC, MSW, and MSWC, it was respectively, 35%, 68%, 17%, and 12% compared to thermally untreated samples. By contrast, o-diphenol oxidase activity was even stimulated by thermal treatment in SS samples, but in the humic extracts, this activity decreased by 75-81%. Urease activity in all humic extracts decreased by 70% or more just at 40 degrees C, whereas for organic wastes, this decrease was observed after treatment at 70 degrees C. Alkaline phosphatase (AP) activity was affected by thermal treatment only in MSW and MSWC. In humic extracts, AP activity decreased gradually to zero except for the MSW extract, where 45% activity was retained after treatment at 70 degrees C. In general, thermostability of enzymes in humic extracts was lower than the materials they were extracted from.
authors.affiliation: Department of Soil and Water Conservation and Organic Resources Management, CEBAS-CSIC, P.O. Box 164, 30100-Espinardo, Murcia, Spain. keijindo@hotmail.com
authors.forename: Keiji
authors.initials: K
authors.lastname: Jindo
authors.forename: José L
authors.initials: JL
authors.lastname: Moreno
authors.forename: Teresa
authors.initials: T
authors.lastname: Hernández
authors.forename: Carlos
authors.initials: C
authors.lastname: García
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D004156:Catechol Oxidase / Q000378:metabolism; D004795:Enzyme Stability; D004798:Enzymes / Q000378:metabolism*; D006812:Humic Substances; D009930:Organic Chemicals / Q000378:metabolism*; D014510:Urease / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism
chemical_list: D004798:Enzymes; D006812:Humic Substances; D009930:Organic Chemicals; D004156:Catechol Oxidase; D000469:Alkaline Phosphatase; D001617:beta-Glucosidase; D014510:Urease