title: Biobleaching of wheat straw-rich soda pulp with alkalophilic laccase from gamma-proteobacterium JB: optimization of process parameters using response surface methodology.
abstract: An alkalophilic laccase from gamma-proteobacterium JB was applied to wheat straw-rich soda pulp to check its bleaching potential by using response surface methodology based on central composite design. The design was employed by selecting laccase units, ABTS (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) concentration and pH as model factors. The results of second order factorial design experiments showed that all three independent variables had significant effect on brightness and kappa number of laccase-treated pulp. Optimum conditions for biobleaching of pulp with laccase preparation (specific activity, 65 nkat mg(-1) protein) were 20 nkat g(-1) of pulp, 2mM ABTS and pH 8.0 which enhanced brightness by 5.89% and reduced kappa number by 21.1% within 4h of incubation at 55 degrees C, without further alkaline extraction of pulp. Tear index (8%) and burst index (18%) also improved for laccase-treated pulp as compared to control raw pulp. Treatment of chemically (CEH1H2) bleached pulp with laccase showed significant effect on release of chromophores, hydrophobic and reducing compounds. Laccase-prebleaching of raw pulp reduced the use of hypochlorite by 10% to achieve brightness of resultant hand sheets similar to the fully chemically bleached pulp.
authors.affiliation: Department of Microbiology, Panjab University, Chandigarh 160014, India.
authors.forename: Gursharan
authors.initials: G
authors.lastname: Singh
authors.forename: Naveen
authors.initials: N
authors.lastname: Ahuja
authors.forename: Mona
authors.initials: M
authors.lastname: Batish
authors.forename: Neena
authors.initials: N
authors.lastname: Capalash
authors.forename: Prince
authors.initials: P
authors.lastname: Sharma
mesh_terms: D020563:Gammaproteobacteria / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D042845:Laccase / Q000032:analysis / Q000378:metabolism*; D008962:Models, Theoretical; D038761:Photobleaching; D018547:Plant Stems / Q000737:chemistry* / Q000378:metabolism; D015203:Reproducibility of Results; D013499:Surface Properties; D014908:Triticum / Q000737:chemistry* / Q000378:metabolism; D014934:Wood
chemical_list: D042845:Laccase