Constructing a cellulosic yeast host with an efficient cellulase cocktail.

Cellulose is a renewable feedstock for green industry. It is therefore important to develop a technique to construct a host with a high cellulolytic efficiency to digest cellulose. In this study, we developed a convenient host-engineering technique to adjust the expression levels of heterologous genes in the host by promoter rearrangement and gene copy number adjustment. Using genes from different glycoside hydrolase (GH) families including GH2, GH3, GH5, GH6, GH7, and GH12 from Aspergillus niger, Trichoderma reesei, and Neocallimastix patriciarum, we constructed a cellulolytic Kluyveromyces marxianus with eight cellulase gene-cassettes that produced a cellulase cocktail with a high cellulolytic efficiency, leading to a significant reduction in enzyme cost in a rice straw saccharification process. Our technique can be used to design a host that can efficiently convert biomass feedstock to biofuel.