Biobleaching of nonwoody pulps using xylanase of Bacillus brevis BISR-062

Optimization, purification, and characterization of xylanase production by a newly isolated Trichoderma harzianum strain by a two-step statistical experimental design strategy

Xylanases are hydrolytic enzymes with a wide range of applications in several industries such as biofuels, paper and pulp, food, and feed. The objective of this study was to optimize the culture conditions and medium components for maximal xylanase production from a newly isolated Trichoderma harzianum strain using the Plackett-Burman Design (PBD) and Box Behnken Design (BBD) experimental strategies. Xylanase production was enhanced 4.16-fold to 153.80 U/ml by BBD compared to a preliminary one-factor-at-a-time (OFAT) activity of 37.01 U/ml and 2.24-fold compared to the PBD (68.70 U/ml). The optimal conditions for xylanase production were: 6 days of fermentation, incubation temperature of 70 °C, pH 5.0, agitation of 160 rpm, and 1.2% wheat bran and ammonium sulphate. The experimental design effectively provided conditions for the production of an acidic-thermostable enzyme with exciting potential for application in animal feed improvement. The acidic-thermostable xylanase was purified from the submerged culture and SDS-PAGE analysis revealed a molecular weight of 72 kDa. This protein had maximum xylanolytic activity at pH 6.0 and 65 °C and was stable for 4 h retaining > 70% activity and exhibited substrate specificity for beechwood xylan with a K_m of 5.56 mg/ml and V_max of 1052.63 µmol/min/mg. Enzyme activity was enhanced by Fe²⁺, Mg²⁺, and Zn²⁺. There was an absence of strong inhibitors of xylanase activity. Overall, these characteristics indicate the potential for at least two industrial applications.

Pulp Enhancement of Oil Palm Empty Fruit Bunches (OPEFBs) via Biobleaching by Using Xylano-Pectinolytic Enzymes of Bacillus amyloliquefaciens ADI2

The present work reports the biobleaching effect on OPEFB pulp upon utilisation of extracellular xylano-pectinolytic enzymes simultaneously yielded from Bacillus amyloliquefaciens ADI2. The impacts of different doses, retention times, pH, and temperatures required for the pulp biobleaching process were delineated accordingly. Here, the OPEFB pulp was subjected to pre-treatment with xylano-pectinolytic enzymes generated from the same alkalo-thermotolerant isolate that yielded those of higher quality. Remarkable enhanced outcomes were observed across varying pulp attributes: for example, enzyme-treated pulp treated to chemical bleaching sequence generated improved brightness of 11.25%. This resulted in 11.25% of less chlorine or chemical consumption required for obtaining pulp with optical attributes identical to those generated via typical chemical bleaching processes. Ultimately, the reduced consumption of chlorine would minimise the organochlorine compounds found in an effluent, resulting in a lowered environmental effect of paper-making processes overall as a consequence. This will undoubtedly facilitate such environmentally-friendly technology incorporation in the paper pulp industry of today.

Application of cellulase-free xylano-pectinolytic enzymes from the same bacterial isolate in biobleaching of kraft pulp

A synergistic action of xylano-pectinolytic enzymes from the same bacterial isolate Bacillus pumilus was evaluated for the prebleaching of kraft pulp. The enzymatic prebleaching of kraft pulp resulted in 8.5% reduction in kappa number of the pulp, showing remarkable delignification with the enzyme treatment. This approach resulted in 25% reduction in active chlorine consumption in subsequent bleaching stages without any decrease in brightness. Increase in Burst factor (9%), Tear factor (4.6%), Breaking length (4.4%), Double fold number (12.5%), Gurley porosity (4%) and Viscosity (11.8%) of enzyme treated pulp reflected the significant improvement in pulp properties. This is the first report describing the use of xylanase and pectinase produced simultaneously in the same production medium from the same bacterial isolate for effective biobleaching of kraft pulp. Use of this xylano-pectinolytic synergism in paper and pulp industry will ultimately help in making the process not only economically feasible but also eco-friendly.

Bleach-boosting effect of crude xylanase from Bacillus stearothermophilus SDX on wheat straw pulp

Pretreatment of wheat straw pulp using cellulase-free xylanase produced from Bacillus stearothermophilus SDX at 60°C for 120min resulted in 4.75% and 22.31% increase in brightness and whiteness, respectively. Enzyme dose of 10U/g of oven dried pulp at pH 9 decreased the kappa number and permanganate number by 7.14% and 5.31%, respectively. Further chlorine dioxide and alkaline bleaching sequences (CDED(1)D(2)) resulted in 1.76% and 3.63% increase in brightness and whiteness, respectively. Enzymatic prebleaching of pulp decreased 20% of chlorine consumption without any decrease in brightness. Improvement in various pulp properties like viscosity, burst factor, burstness, breaking length, double fold, gurley porosity, tear factor, and tearness were also observed after bleaching of xylanase treated wheat straw pulp.