Strategies for Using Pulp and Paper Sludges as Culture Media for Xylanase Production with Bacillus pumilus
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Fermentation of Bacillus pumilus (B. pumilus) using different pulp and paper sludges as culture media were performed in this work to produce at lower cost industrial enzymes such as xylanases. Secondary sludge was shown to be a suitable alternative culture medium for B. pumilus growth, while primary sludge may serve as xylanases inducer. Mixing primary (PS) and secondary sludges (SS) at 1PS:2SS (w/w) ratio having 15 g/L total solids concentration resulted in the highest cell concentration of 2 × 108 CFU/mL and the highest xylanase activity of 3.8 IU/mL under shake flask fermentation. Other lignocellulosic biomasses were tested as potential xylanase inducers. Addition of corn stover to SS showed the highest xylanase activity (10.7 IU/mL). When using a 7 L bioreactor, total cell concentration and xylanase activity obtained in the secondary sludge medium supplemented with commercial xylan (2.5 × 109 CFU/mL and 35.5 IU/mL, respectively) and corn stover (3.4 × 109 CFU/mL and 37.8 IU/mL, respectively) were comparative to a semi-synthetic based medium (5.8 × 109 CFU/mL and 47 IU/mL, respectively). The xylanase activity of B. pumilus produced in paper sludge is stable at pH 6–9 at 50 °C that offered a potential application of the enzyme for biobleaching in pulp and paper industry.
KeywordsBacillus pumilus Xylanase Pulp and paper sludge Lignocellulosic biomass
The authors are sincerely thankful to the Natural Sciences and Engineering Research Council of Canada (Grant No. 371821) for financial support. The views and opinions expressed in this article are those of authors. We would like to extend our thanks to Mr. Brice Ouedraogo for experimental assistance.
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