The present invention provides for heterologous expression of beta-glucosidase (BGL) polypeptides encoded by Humicola grisea, Candida wickerhamii, Aspergillus aculeatus, Aspergillus oryzae, Penicillium decumbens, Chaetomium globosum, Neocallimastix frontalis, Debaryomyces hansenii, Kluyveromyces marxianus, or Phytophthora infestans in host cells, such as the yeast Saccharomyces cerevisiae. The expression in such host cells of the corresponding genes, and variants and combinations thereof, result in improved specific activity of the expressed BGL. Thus, such genes and expression systems are useful for efficient and cost-effective consolidated bioprocessing systems.