title: Use of response surface methodology to evaluate the extraction of Debaryomyces hansenii xylose reductase by aqueous two-phase system.
abstract: Xylose reductase (XR) from Debaryomyces hansenii was extracted by partitioning in aqueous two-phase systems (ATPS) composed of polyethylene glycol (PEG) 4000 in the presence of different salts, specifically sodium sulfate, lithium sulfate and potassium phosphate. Batch extractions were carried out under different conditions of temperature (25-45 degrees C) and tie-line length (TLL) for each system, according to a central composite design face-centered of 36 tests, and the response surface methodology was used to evaluate the results. Quadratic polynomial models were adjusted to the data to predict the behavior of four responses, namely the XR partition coefficient (K(XR)), the selectivity (S), the purification factor (PF(T)) and the activity yield (Y(T)) in the top phase. The optimal extraction conditions were found using the PEG 4000/sodium sulfate system at 45 degrees C and TLL=25.1, which ensured PF(T)=3.1 and Y(T)=131%. The ATPS proved effective for partial purification of D. hansenii xylose reductase in cell-free crude extract, and the response surface methodology revealed to be an appropriate and powerful tool to determine the best dominion of temperature and ATPS composition.
authors.affiliation: Department of Food Technology, Federal University of Viçosa, Av. P. H. Rolfs s/n, 36571-000 Viçosa, Minas Gerais, Brazil.
authors.forename: Janaína Teles
authors.initials: JT
authors.lastname: de Faria
authors.forename: Fábio Coelho
authors.initials: FC
authors.lastname: Sampaio
authors.forename: Attilio
authors.initials: A
authors.lastname: Converti
authors.forename: Flávia M Lopes
authors.initials: FM
authors.lastname: Passos
authors.forename: Valéria Paula Rodrigues
authors.initials: VP
authors.lastname: Minim
authors.forename: Luis Antônio
authors.initials: LA
authors.lastname: Minim
mesh_terms: D000449:Aldehyde Reductase / Q000302:isolation & purification* / Q000378:metabolism; D005591:Chemical Fractionation / Q000379:methods*; D055165:Debaryomyces / Q000201:enzymology* / Q000378:metabolism; D005656:Fungal Proteins / Q000302:isolation & purification* / Q000378:metabolism; D016014:Linear Models; D018020:Lithium Compounds / Q000737:chemistry; D008956:Models, Chemical; D015233:Models, Statistical; D010710:Phosphates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D013696:Temperature
chemical_list: D005656:Fungal Proteins; D018020:Lithium Compounds; D010710:Phosphates; D017680:Potassium Compounds; D013431:Sulfates; C012036:sodium sulfate; D011092:Polyethylene Glycols; C054097:lithium sulfate; C013216:potassium phosphate; D000449:Aldehyde Reductase