Fungal β-glucosidase expression in Saccharomyces cerevisiae

Recombinant Saccharomyces cerevisiae strains expressing beta-glucosidases from Thermoascus aurantiacus (Tabgl1) and Phanerochaete chrysosporium (PcbglB and Pccbgl1) were constructed and compared to S. cerevisiae Y294[SFI], previously identified as the best beta-glucosidase-producing strain. The PcbglB was also intracellularly expressed in combination with the lac12 lactose permease of Kluyveromyces lactis in S. cerevisiae Y294[PcbglB + Lac12]. The recombinant extracellular beta-glucosidases indicated maximum activity in the pH range 4-5 and temperature optima varying from 50 to 75 A degrees C. The S. cerevisiae Y294[Pccbgl1] strain performed best under aerobic and anaerobic conditions, producing 2.6 times more beta-glucosidase activity than S. cerevisiae Y294[SFI] and an ethanol concentration of 4.8 g l(-1) after 24 h of cultivation on cellobiose as sole carbohydrate source. S. cerevisiae Y294[Tabgl1] was unable to grow on cellobiose (liquid medium), whereas S. cerevisiae Y294[PcbglB + Lac12] exhibited limited growth.