Researchers Develop New Strain of Yeast That Can More Efficiently Ferment 5-Carbon Sugars from Lignocellulosic Feedstocks
A team of European researchers has used evolutionary engineering as a complement to rationally-designed genetic engineering to develop a new strain of the industrial yeast Saccharomyces cerevisiae) that can efficiently ferment pentose sugars (xylose and arabinose), as found in lignocellulosic feedstocks. A paper on their work was published 15 June in BioMed Central’s open access journal Biotechnology for Biofuels.
Such feedstocks, in particular agricultural wastes and hardwoods, contain a large fraction of the pentose sugars D-xylose and L-arabinose; cost-efficient fermentation of lignocellulosic hydrolysates to ethanol requires a microorganism that can ferment pentose sugars to ethanol with high yield and productivity. While S. cerevisiae is the conventional microorganism for ethanol production, it cannot naturally ferment pentose sugars.
Although other work has used metabolic to express both fungal and bacterial genes encoding either D-xylose or L-arabinose utilizing pathways in the yeast, the results have not been optimal, the authors note.
The team took a recombinant strain (TMB3061) previously engineered with integrated genes for xylose and arabinose co-utilization, and grew it on a mixture of xylose and arabinose sugars to select a stable population most capable of metabolizing the pentose feedstock.
The evolved strain TMB3130 displayed an enhanced aerobic growth rate on xylose (three- to fourfold) and on arabinose (twofold) compared with its parental strain TMB3061.
Evolutionary engineering was used to improve the simultaneous conversion of xylose and arabinose to ethanol in a recombinant industrial Saccharomyces cerevisiae strain carrying the heterologous genes for xylose and arabinose utilization pathways integrated in the genome. The evolved strain TMB3130 displayed an increased consumption rate of xylose and arabinose under aerobic and anaerobic conditions. Improved anaerobic ethanol production was achieved at the expense of xylitol and glycerol but arabinose was almost stoichiometrically converted to arabitol.
—Sanchez et al.
Rosa Garcia Sanchez, Kaisa Karhumaa, Cesar Fonseca, Violeta Sanchez Nogue, Joao RM Almeida, Christer U Larsson, Oskar Bengtsson, Maurizio Bettiga, Barbel Hahn-Hagerdal and Marie F Gorwa-Grauslund (2010) Improved xylose and arabinose utilization by an industrial recombinant Saccharomyces cerevisiae strain using evolutionary engineering. Biotechnology for Biofuels doi: 10.1186/1754-6834-3-13