Enhanced ethanol production from paper sludge waste under high-solids conditions with industrial and cellulase-producing strains of Saccharomyces cerevisiae

[Display omitted] •Three industrial yeast strains compared in high-solids paper sludge fermentation.•Highest ethanol titre of 101.8 g/L achieved using paper sludge from virgin pulping.•Xylose utilisation by engineered strain Cellusec® 1.0 improved ethanol titre by 10.3%.•Required enzyme dosage reduced by 50% using cellulase-secreting strain Cellusec® 2.0. Reported ethanol titres from hydrolysis-fermentation of the degraded fibres in paper sludge (PS) waste, generally obtained under fed-batch submerged conditions, can be improved through fermentation processes at high solids loadings, as demonstrated in the present study with two industrial PS wastes at enzyme dosages appropriate for solids loadings up to 40% (w/w). The industrial yeast,Saccharomyces cerevisiaestrain Ethanol Red®, was compared to two genetically engineeredS. cerevisiaestrains, namely Cellusec® 1.0 and Cellusec® 2.0, capable of xylose utilisation, and xylose utilisation and cellulase production, respectively. High-solids batch fermentations were conducted in 3 L horizontal rotating reactors and ethanol titres of 100.8 and 73.3 g/L were obtained for virgin pulp and corrugated recycle PS, respectively, at 40% (w/w) solids loading using Ethanol Red®. Xylose utilisation by Cellusec® 1.0 improved ethanol titres by up to 10.3%, while exogenous cellulolytic enzyme requirements were reduced by up to 50% using cellulase-producing Cellusec® 2.0.