Authors: Adnan Cavka Björn Alriksson Shaunita H Rose Willem H van Zyl Leif J Jönsson
Publish Date: 2010/09/08
Volume: 38, Issue: 8, Pages: 891-899
Abstract
The possibility to utilize fiber sludge waste fibers from pulp mills and lignocellulosebased biorefineries for combined production of liquid biofuel and biocatalysts was investigated Without pretreatment fiber sludge was hydrolyzed enzymatically to monosaccharides mainly glucose and xylose In the first of two sequential fermentation steps the fiber sludge hydrolysate was fermented to cellulosic ethanol with the yeast Saccharomyces cerevisiae Although the final ethanol yields were similar the ethanol productivity after 95 h was 33 g/l/h for the fiber sludge hydrolysate compared with only 22 g/l/h for a reference fermentation with similar sugar content In the second fermentation step the spent fiber sludge hydrolysate the stillage obtained after distillation was used as growth medium for recombinant Aspergillus niger expressing the xylanaseencoding Trichoderma reesei Hypocrea jecorina xyn2 gene The xylanase activity obtained with the spent fiber sludge hydrolysate 8500 nkat/ml was higher than that obtained in a standard medium with similar monosaccharide content 1400 nkat/ml Analyses based on deglycosylation with Nglycosidase F suggest that the main part of the recombinant xylanase was unglycosylated and had molecular mass of 207 kDa while a minor part had Nlinked glycosylation and molecular mass of 236 kDa Chemical analyses of the growth medium showed that important carbon sources in the spent fiber sludge hydrolysate included xylose small aliphatic acids and oligosaccharides The results show the potential of converting waste fiber sludge to liquid biofuel and enzymes as coproducts in lignocellulosebased biorefineriesThe assistance of Marcus Jonsson in performing preliminary experiments is gratefully acknowledged One of the authors AC was supported by SEKAB ETechnology Örnsköldsvik Sweden through the Umeå University Industrial Post Graduate School The research received financial support from the Kempe Foundations the Knut and Alice Wallenberg Foundation the Biorefinery of the Future wwwbioraffinaderise and the Bio4Energy research initiative wwwbio4energyse
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