Researchers Identify Sugar Transporters in Aspergillus nidulans

Enzymatic deconstruction of lignocellulose, catalyzed by fungi such as Aspergillus nidulans, releases a mixture of sugars for fermentation into ethanol. However, a major drawback is the inability of yeast to successfully consume sugars other than glucose. The team of Thaila Fernanda dos Reis from Universidade de São Paulo in Brazil screened the genome of A. nidulans for transporters capable of consuming non-glucose sugars, and introduced them into Saccharomyces cerevisiae.

The team identified two proteins in A. nidulans, CltA, and CltB, with roles in cellobiose transport and cellulose signaling, respectively. CltA conferred growth on low and high concentrations of cellobiose to the S. cerevisiae. Meanwhile, CltB was not able to confer growth on cellobiose, but the introduction of additional functional copies of CltB increased the growth in the presence of low concentrations of cellobiose, indicating its ability to transport cellobiose. Furthermore, a previously identified glucose transporter, HxtB, was also found to be a major xylose transporter in A. nidulans. In S. cerevisiae, HxtB conferred growth on xylose which was accompanied by ethanol production.

This study serves as basis for future research on engineering Aspergillus spp. to consume other carbon sources or to improve transport and fermentation of non-glucose sugars in S. cerevisiae.