Biomass to biofuel : towards the bioengineering of Saccharomyces species for cellulose degradation

Abstract

Cellulose is the most abundant polysaccharide on earth and therefore represents a major reservoir of sugar that could be potentially converted to alcohol and used as a fuel source. The filamentous fungus Trichoderma reesei possesses an array of enzymes which can degrade cellulose to glucose. These enzymes are known as cellulases. The aim of this project was to combine the fermentative capacity of Saccharomyces yeast species with the cellulolytic ability of the T. reesei to simultaneously saccharify and ferment a cellulose substrate into ethanol. Three cellulolytic genes of T. reesei eg11, cbh2 and bg11 were cloned separately into the haploid S. cerevisiae strain S150 and also into the polyploid S. pastorianus strain C10-51. Experiments were carried out in parallel to created cellulase encoding cassettes of eg11, cbh2 and bg11 using either T. reesei genomic DNA (gDNA) or complementary DNA (cDNA). The gDNA inserts were amplified by polymerase chain reaction (PCR) using gene specific oligonucleotide primers. The cDNA inserts were synthesised from T. reesei RNA by reverse-transcription PCR (RT-PCR).