Valorizing recycled paper sludge by a bioethanol production process with cellulase recycling.
The feasibility of cellulase recycling in the scope of bioethanol production from recycled paper sludge (RPS), an inexpensive byproduct with around 39% of carbohydrates, is analyzed. RPS was easily converted and fermented by enzymes and cells, respectively. Final enzyme partition between solid and liquid phases was investigated, the solid-bound enzymes being efficiently recovered by alkaline washing. RPS hydrolysis and fermentation was conducted over four rounds, recycling the cellulases present in both fractions. A great overall enzyme stability was observed: 71, 64 and 100% of the initial Cel7A, Cel7B and β-glucosidase activities, respectively, were recovered. Even with only 30% of fresh enzymes added on the subsequent rounds, solid conversions of 92, 83 and 71% were achieved for the round 2, 3 and 4, respectively. This strategy enabled an enzyme saving around 53-60%, while can equally contribute to a 40% reduction in RPS disposal costs.
Centre of Biological Engineering - University of Minho, Campus de Gualtar - 4710-057 Braga, Portugal.
Daniel
D
Gomes
Centre of Biological Engineering - University of Minho, Campus de Gualtar - 4710-057 Braga, Portugal. Electronic address: luciliad@deb.uminho.pt.
Lucília
L
Domingues
Centre of Biological Engineering - University of Minho, Campus de Gualtar - 4710-057 Braga, Portugal.
Miguel
M
Gama
D056804:Biofuels; D019149:Bioreactors; D044602:Cellulases / Q000096:biosynthesis / Q000737:chemistry*; D004795:Enzyme Stability; D000431:Ethanol / Q000138:chemical synthesis*; D005285:Fermentation; D006868:Hydrolysis; D010209:Paper; D059027:Recycling; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000737:chemistry*
D056804:Biofuels; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol; D044602:Cellulases
Alkaline wash; Cellulase recycling; Cellulosic bioethanol; Recycled paper sludge; Ultrafiltration