Bio-conventional bleaching of kadam kraft-AQ pulp by thermo-alkali-tolerant xylanases from two strains of Coprinellus disseminatus for extenuating adsorbable organic halides and improving strength with optical properties and energy conservation.

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.

Bio-conventional bleaching of wheat straw soda-AQ pulp with crude xylanases from SH-1 NTCC-1163 and SH-2 NTCC-1164 strains of Coprinellus disseminatus to mitigate AOX generation.

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.

Production of high level of cellulase-poor xylanases by wild strains of white-rot fungus Coprinellus disseminatus in solid-state fermentation.

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.