Enhancement of xylose fermentation in Saccharomyces cerevisiae via integration of a kinase-phosphatase redox cofactor balancing system

Xylose is one of the most abundant sugars in nature and makes up a significant portion of lignocellulose. In order to profitably use lignocellulosic biomass for sustainably producing ethanol and other chemicals, it is important that all of its sugars be efficiently co-fermented. The current organism of choice for such fermentations, Saccharomyces cerevisiae (Baker’s yeast), is unable to do so given its poor consumption of xylose. Engineered strains of S. cerevisiae have arisen from the introduction of a xylose reductase-xylitol dehydrogenase (XR-XDH) pathway native to other fungi, which allows yeast to better metabolize xylose. However, under anaerobic conditions, the XR-XDH pathway leads to an imbalance of the redox cofactors NADH and NAD+. The goal of this study is to introduce a kinase-phosphatase system into S. cerevisiae which recycles NADH independently of the presence of oxygen, thereby reducing the accumulation of certain intermediates as well as by-products of the XR-XDH pathway. This is expected to increase significantly the ethanol yield from xylose, enabling subsequent engineering approaches for the production of other value-added chemicals.

Faculty Supervisor:

Radhakrishnan Mahadevan

Student:

Partner:

Lund University

Discipline:

Engineering

Sector:

Education

University:

University of Toronto

Program: