alexa Bioconversion of kraft paper mill sludges to ethanol by SSF and SSCF.
Chemical Engineering

Chemical Engineering

Journal of Bioprocessing & Biotechniques

Author(s): Kang L, Wang W, Lee YY

Abstract Share this page

Abstract Paper mill sludge is a solid waste material composed of pulp residues and ash generated from pulping and paper making processes. The carbohydrate portion of the sludge has chemical and physical characteristics similar to pulp. Because of its high carbohydrate content and well-dispersed structure, the sludges can be biologically converted to value-added products without pretreatment. In this study, two different types of paper mill sludges, primary sludge and recycle sludge, were evaluated as a feedstock for bioconversion to ethanol. The sludges were first subjected to enzymatic conversion to sugars by commercial cellulase enzymes. The enzymatic conversion was inefficient because of interference by ash in the sludges with the enzymatic reaction. The main cause was that the pH level is dictated by CaCO3 in ash, which is two units higher than the pH optimum of cellulase. To alleviate this problem, simultaneous saccharification and cofermentation (SSCF) using cellulase (Spezyme CP) and recombinant Escherichia coli (ATCC-55124), and simultaneous saccharification and fermentation (SSF) using cellulase and Saccharomyces cerevisiae (ATCC-200062) were applied to the sludges without any pretreatment. Ethanol yields of 75-81\% of the theoretical maximum were obtained from the SSCF on the basis of total carbohydrates. The yield from the SSF was also found to be in the range of 74-80\% on the basis of glucan. The SSCF and SSF proceeded under stable condition with the pH staying near 5.0, close to the optimum for cellulase. Decrease of pH occurred due to carbonic acid and other organic acids formed during fermentation. The ash was partially neutralized by the acids produced from the SSCF and SSF and acted as a buffer to stabilize the pH during fermentation. When the SSF and SSCF were operated in fed-batch mode, the ethanol concentration in the broth increased from 25.5 and 32.6 g/L (single feed) to 45 and 42 g/L, respectively. The ethanol concentration was limited by the tolerance of the microorganism in the case of SSCF. The ethanol yield in fed-batch operation decreased to 68\% for SSCF and 70\% for SSF. The high-solids condition in the bioreactor appears to create adverse effects on the cellulase reaction. This article was published in Appl Biochem Biotechnol and referenced in Journal of Bioprocessing & Biotechniques

Relevant Expert PPTs

Relevant Speaker PPTs

Recommended Conferences

  • International Conference on Nanobiotechnology
    July 10-11, 2017 CHICAGO, USA
  • Global Biotechnology Congress 2017
    July 10th - 13th, 2017, Boston, MA, USA
  • 17th Euro Biotechnology Congress
    September 25-27, 2017 Berlin, Germany
  • 2nd World Biotechnology Congress
    December 04-06, 2017 Sao Paulo, Brazil

Relevant Topics

Peer Reviewed Journals
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals
International Conferences 2017-18
Meet Inspiring Speakers and Experts at our 3000+ Global Annual Meetings

Contact Us

© 2008-2017 OMICS International - Open Access Publisher. Best viewed in Mozilla Firefox | Google Chrome | Above IE 7.0 version