Engineered Yeasts for the Simultaneous Fermentation of Galactose and Cellobiose in Seaweed Hydrolyzates

Seaweeds are considered as potential feedstock for biofuel production due to their high growth rates. The major sugar components in seaweeds which can be fermented to ethanol are glucose and galactose. However, in the fermentation of these sugars to bioethanol using current strains of yeast, galactose is only consumed after the glucose is depleted; thus, making the process inefficient.

Researchers from the University of Illinois (USA) recently engineered a new strain of Saccharomyces cerevisiae that is capable of  simultaneously fermenting galactose and cellobiose (i.e. a dimeric form of glucose). In their study, the researchers introduced to the yeast,  a gene which expresses a new sugar transporter and an enzyme that breaks down cellobiose at the intracellular level. Coupled with a modified process for the hydrolysis of seaweeds that produces cellobiose (instead of glucose) and galactose, biofuel production from seaweeds using this new yeast strain could become more efficient. This discovery, according to the researchers, greatly enhances the economic viability of marine biofuels for commercialization. The full paper is published in the journal, Applied and Environmental Microbiology (URL above).