Valorisation of Waste-Paper Streams to Ethanol Through Submerged Fermentation

Abstract Three unrecyclable waste-paper streams, namely label backing paper (LB), multilayer paper-based packaging (ML) and potato paper sacks (PS) were characterised as fermentation feedstocks. Industrial Saccharomyces cerevisiae strain Ethanol Red® and recombinant S. cerevisiae strains Cellusec® 2.0 and Cellusec® 3.3 engineered for both cellulase-secretion and xylose utilisation were compared. Fermentation performance using Ethanol Red® with batch simultaneous saccharification and fermentation (SSF) was higher compared to separate hydrolysis and fermentation (SHF), and pre-saccharification and SSF (PSSF). Shake flask fed-batch SSF at 30% (w/w) final solid loading produced the highest ethanol titres of 75.01, 49.9 and 82.81 g/L for untreated LB, ML and PS, respectively, and yields above 70% of the theoretical maximum, at an enzyme dosage of 10 FPU/g dry solids (ds), using Ethanol Red ® . However, Cellusec® 2.0 and 3.3 in batch SSF at a two-to-three-fold reduced exogenous enzyme requirement of 3.5 FPU/g ds, achieved ethanol titres and yields higher than Ethanol Red ® . Graphical Abstract