Functional characterization of novel transporters from Trichoderma reesei involved in the uptake of sugars from lignocellulosic biomass

Author(s)

Vanessa Mendes

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2023-07-13

Examining board members

Roberto do Nascimento Silva; Leandro Vieira Santos; Richard John Ward

• Advisor: Roberto do Nascimento Silva

Abstract

The global interest in reducing the environmental and economic impacts associated with the use of fossil fuels advocates new, renewable, and low-cost energy sources. In this scenario, second-generation ethanol (2G) emerges as a promising alternative when using lignocellulosic biomass (LCB) as feedstock. However, the deconstruction of BLCs and the fermentation of sugars resulting from this process are some of the challenges to be overcome for an economically viable production of 2G ethanol. Lignocellulolytic fungi, such as T. reesei are industrially exploited due to their potential to produce and secrete holocellulases (cellulases and hemicellulases). On the other hand, T. reesei possesses a complex transport system responsible for the effective transport of sugars derived from LCBs, which act as inducers or repressors of holocellulase biosynthesis. Despite the notable interest of this fungus in the bioenergy industry, the sugar transport system of T. reesei remains largely unexplored. Thus, a better understanding of T. reesei transporters can be a valuable strategy to design improved strains of interest to the 2G industry and overcome the production challenges of bioethanol. In this study intends to shed light on this subject through the functional characterization of new T. reesei transporters. Initially, our phylogenetic analyzes and molecular docking indicated the potential of the new T. reesei transporters to carry the essential sugars of holocellulose (xylose, cellobiose, mannose and glucose). The functional validation was carried out through the heterologous expression of the transporters in microbial platforms (EBY.VW4000 and SC9721) that do not present a functional transport system for these sugars. In this way, it was possible to characterize three xylose transporters (Tr54632, Tr68122, and Tr79202) and one cellobio-oligosaccharide transporter (Tr441745). In addition, the expression Tr54632 and Tr79202 transporters supported low growth of the yeast EBY.VW4000 in other holocellulosic sugars, such as glucose and mannose, respectively. Meanwhile, the yeast harboring Tr44175 was able to carry sophorose, a carbon source that induces the expression of hocellulases. The present work characterized transporters for which no transport activity had been previously described; thus, new paths are opened for the strains engineering with applications in the bioenergy industry. (AU)

• FAPESP's process: 18/07984-0 - Characterization of new sugar transporters of Trichoderma reesei and heterologous expression in an industrial strain of Saccharomyces cerevisiae
• Grantee: Vanessa Mendes
• Support Opportunities: Scholarships in Brazil - Doctorate