The cellulose utilization pathways and cellulase cocktail formulation. (A) The fungal cellulose utilization systems in yeast during simultaneous saccharification and fermentation of cellulose. (B) The filter paper activity (FPA) assay of potential enzyme synergistic effects with the crude enzyme of KR5. Several different commercial cellulases, including EG (EglA and EGIII), CBH (CBHI and CBHII) and BGL (purified NpaBGS), were used for cocktails with the supernatants of KR5 by mixing equivalent proportions of volume individually. One unit of FPA is defined as one μmol reducing sugar released from filter paper in one minute. The cellodextrin transport pathway includes a cellodextrin transporter (CDT) and intracellular cellulases (EG, CBH, and BGL). The sugar catabolism pathway present in yeasts includes hexose transporters (HXT) and lactose permease (LP). In SSF, pretreatment and extracellular cellulase cocktail process may both be used.