title: Bacillus licheniformis proteases as high value added products from fermentation of wastewater sludge: pre-treatment of sludge to increase the performance of the process.
abstract: Wastewater sludge is a complex raw material that can support growth and protease production by Bacillus licheniformis. In this study, sludge was treated by different thermo-alkaline pre-treatment methods and subjected to Bacillus licheniformis fermentation in bench scale fermentors under controlled conditions. Thermo-alkaline treatment was found to be an effective pre-treatment process in order to enhance the proteolytic activity. Among the different pre-treated sludges tested, a mixture of raw and hydrolysed sludge caused an increase of 15% in the protease activity, as compared to the untreated sludge. The benefit of hydrolysis has been attributed to a better oxygen transfer due to decrease in media viscosity and to an increase in nutrient availability. Foam formation was a major concern during fermentation with hydrolysed sludge. The studies showed that addition of a chemical anti-foaming agent (polypropylene glycol) during fermentation to control foam could negatively influence the protease production by increasing the viscosity of sludge.
authors.affiliation: Institut National de la Recherche Scientifique, Centre Eau, Terre et Environnement, Université du Québec, 490 de la Couronne, Quebec, G1K 9A9, Canada. mathieu.drouin@ete.inrs.ca
authors.forename: M
authors.initials: M
authors.lastname: Drouin
authors.forename: C K
authors.initials: CK
authors.lastname: Lai
authors.forename: R D
authors.initials: RD
authors.lastname: Tyagi
authors.forename: R Y
authors.initials: RY
authors.lastname: Surampalli
mesh_terms: D000693:Anaerobiosis; D001407:Bacillus / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000378:metabolism; D015169:Colony Count, Microbial; D010450:Endopeptidases / Q000096:biosynthesis* / Q000378:metabolism; D005285:Fermentation; D006868:Hydrolysis; D012722:Sewage / Q000382:microbiology*; D013696:Temperature; D014783:Viscosity
chemical_list: D001426:Bacterial Proteins; D012722:Sewage; D010450:Endopeptidases; C087822:alkaline protease