In silico structural analysis of xylose transporters from Trichoderma reesei and their applications on bioethanol production

Second-generation ethanol (2G ethanol) has arisen as a renewable and sustainable energy alternative to conventional fossil fuels. Its production is divided in many steps with economic challenges. In this context, xylose transporters have been a focus of studies aiming to contribute to overcoming these challenges to be overcome. Regarding the optimization of the fermentation stage, one of the biggest obstacles is due to Saccharomyces cerevisiae, the main organism used in fermentation, does not possess an efficient xylose transport system. With this, the heterologous expression of xylose transporters along with the xylose metabolic pathway in S. cerevisiae has been a target of study to increase the fermentative performance for ethanol 2G production. Since lignocellulosic substrates present mixtures with high contents of glucose and xylose, ensuring efficient transport of the pentose without competition with hexose due to an intrinsic nonspecificity of the transporters, is fundamental to achieving improved ethanol productivity. However, most of sugar transporters characterized as xylose transporters generally have a higher affinity for glucose than for xylose. Therefore, many studies analyze the sequence of these transporters in order to understand the amino acids involved and find targets for protein engineering, trying to increase the affinity for pentose.