title: Statistical optimization of thermo-tolerant xylanase activity from Amazon isolated Bacillus circulans on solid-state cultivation.
abstract: A 2(2) factorial design was performed to find the best conditions of pH and temperature for xylanolytic activity of Bacillus circulans BL53 isolated from the Amazon environment. Solid-state cultivation was carried out on an inexpensive, abundant agro-industrial soybean residue. The central composite design (CCD) used for the analysis of treatment combinations showed that a second-order polynomial regression model was in good agreement with experimental results, with R(2) = 0.9369 (P < 0.05). The maximum activity was obtained at a high temperature (80 degrees C) and over a large pH range (4.0-7.0). Enzymatic activity was maintained in heated extracts up to 50 degrees C, suggesting that the xylanases of B. circulans BL53 are thermo-tolerant biocatalysts, being of interest for industrial processes. The crude enzyme extract hydrolyzed rice straw, sugar cane bagasse and soybean fiber and its activity was stimulated by Co(2+), Fe(3+), and beta-mercaptoethanol but inhibited by Mn(2+), Cu(2+), Ca(2+), Zn(2+), Ba(2+), Mg(2+) and by EDTA.
authors.affiliation: Food Science and Technology Institute, Federal University of Rio Grande do Sul State, Porto Alegre, RS, Brazil.
authors.forename: Júlio Xandro
authors.initials: JX
authors.lastname: Heck
authors.forename: Simone Hickmann
authors.initials: SH
authors.lastname: Flôres
authors.forename: Plinho Francisco
authors.initials: PF
authors.lastname: Hertz
authors.forename: Marco Antônio Záchia
authors.initials: MA
authors.lastname: Ayub
mesh_terms: D001407:Bacillus / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification*; D001431:Bacteriological Techniques; D001938:Brazil; D043364:Endo-1,4-beta Xylanases / Q000378:metabolism*; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000379:methods*; D013025:Glycine max; D013223:Statistics as Topic; D013696:Temperature
chemical_list: D043364:Endo-1,4-beta Xylanases