Xylitol production from lignocellulosic whole slurry corn cob by engineered industrial Saccharomyces cerevisiae PE-2

In this work, the industrial Saccharomyces cerevisiae PE-2 strain, presenting innate capacity for xylitol accumulation, was engineered for xylitol production by overexpression of the endogenous GRE3 gene and expression of different xylose reductases from Pichia stipitis. The best-performing GRE3-overexpressing strain was capable to produce 148.5g/L of xylitol from high xylose-containing media, with a 0.95g/g yield, and maintained close to maximum theoretical yields (0.89g/g) when tested in non-detoxified corn cob hydrolysates. Furthermore, a successful integrated strategy was developed for the production of xylitol from whole slurry corn cob in a presaccharification and simultaneous saccharification and fermentation process (15% solid loading and 36FPU) reaching xylitol yield of 0.93g/g and a productivity of 0.54g/L·h. This novel approach results in an intensified valorization of lignocellulosic biomass for xylitol production in a fully integrated process and represents an advance towards a circular economy.This study was supported by the Portuguese Foundation for Science and Technology (FCT, Portugal) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-010145-FEDER-006684/POCI-01-0145-FEDER-007440), the BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte and the MultiBiorefinery project (POCI01–0145-FEDER-016403). Sara L. Baptista (SFRH/BD/132717) and Joana T. Cunha (PD/BD/128247/2016) thanks FCT and MIT-Portugal Program for their doctoral fellowships, respectively. We also thank Prof. Björn Johansson (University of Minho) for providing the p417 and p418 plasmids used in thi sstudy and the student Daniel Núñez for some of the experiments required for Fig. 3.