RESUMO
Two novel thermo-alkali-tolerant crude xylanases namely MLK-01 (enzyme-A) and MLK-07 (enzyme-B) from Coprinellus disseminatus mitigated kappa numbers of Anthocephalus cadamba kraft-AQ pulps by 32.5 and 34.38%, improved brightness by 1.5 and 1.6% and viscosity by 5.75 and 6.47% after (A)XE(1) and (B)XE(1)-stages, respectively. The release of reducing sugars and chromophores was the highest during prebleaching of A. cadamba kraft-AQ pulp at enzyme doses of 5 and 10 IU/g, reaction times 90 and 120 min, reaction temperatures 75 and 65°C and consistency 10% for MLK-01 and MLK-07, respectively. MLK-07 was more efficient than MLK01 in terms of producing pulp brightness, improving mechanical strength properties and reducing pollution load. MLK-01 and MLK-07 reduced AOX by 19.51 and 42.77%, respectively at 4% chlorine demands with an increase in COD and colour due to removal of lignin carbohydrates complexes. A. cadamba kraft-AQ pulps treated with xylanases from MLK-01 to MLK-07 and followed by CEHH bleaching at half chlorine demand (2%) showed a drastic reduction in brightness with slight improvement in mechanical strength properties compared to pulp bleached at 4% chlorine demand. MLK-01 reduced AOX, COD and colour by 43.83, 39.03 and 27.71% and MLK-07 by 38.34, 40.48 and 30.77%, respectively at half chlorine demand compared to full chlorine demand (4%). pH variation during prebleaching of A. cadamba kraft-AQ pulps with strains MLK-01 and MLK-07 followed by CEHH bleaching sequences showed a decrease in pulp brightness, AOX, COD and colour with an increase in mechanical strength properties, pulp viscosity and PFI revolutions to get a beating level of 35 ± 1 °SR at full chlorine demand.
Assuntos
Agaricales/enzimologia , Compostos Orgânicos/metabolismo , Rubiaceae/metabolismo , Xilosidases/metabolismo , Cloro/metabolismo , Concentração de Íons de Hidrogênio , Temperatura , Fatores de Tempo , Xilosidases/isolamento & purificaçãoRESUMO
Two novel cellulase-poor xylanases from Coprinellus disseminatus SH-1 NTCC-1163 (enzyme-A) and SH-2 NTCC-1164 (enzyme-B) produced under solid-state fermentation mitigated kappa number of wheat straw soda-AQ pulps by 24.38 and 27.94% respectively after XE stages. The release of reducing sugars and chromophores was highest for both the enzymes at 10IU/g and reaction time 180min for 55°C at variable consistencies that is, 10% for enzyme-A and 5% for enzyme-B. (A)XECEHH and (B)XECEHH sequences improved brightness by 5.17 and 2.58% respectively at 4.5% chlorine charge. AOX in (A)XECEHH and (B)XECEHH sequences reduced by 56.11 and 55.75% respectively at 4.5% chlorine charge and 68.34 and 67.98% respectively at 2.25% chlorine charge respectively compared to control. Both the enzymes showed improvement in double fold and tear index with a decrease in burst and tensile index. SEM showed peeling, cracking and delamination in fibers due to enzyme treatment thus facilitating the penetration of bleach chemicals.
Assuntos
Agaricales/enzimologia , Biotecnologia/métodos , Clareadores/metabolismo , Endo-1,4-beta-Xilanases/metabolismo , Halogênios/isolamento & purificação , Papel , Triticum/química , Adsorção , Carboidratos/análise , Fenômenos Mecânicos , Microscopia Eletrônica de Varredura , Fatores de Tempo , Viscosidade , Eliminação de Resíduos LíquidosRESUMO
The production, optimisation and partial characterisation of xylanases from newly isolated wild strains of Coprinellus disseminatus was performed in solid-state fermentation. Strains SH-1 and SH-2 showed high xylanase (727.78 and 227.99 IU/mL) with very low CMCase (0.925 and 0.660 IU/mL) and laccase (0.640 and 0.742 U/mL) activities at incubation time seven days, 37 degrees C and initial pH 6.4, using yeast extract as nitrogen source and cheap substrate (wheat bran), which increased the cost effectiveness of the process. Crude cellulase-poor xylanases obtained from test strains showed maximum activities at 55 degrees C and pH 6.4 and retained 32.64 (SH-1) and 35.03% (SH-2) activity at pH 8 and 43.01 (SH-1) and 25.00% (SH-2) activity at 65 degrees C. As test strains produced high level of cellulase-poor xylanases, which were active over a wide range of temperature and pH, these enzymes might be used as pulp biobleaching agents.