Fungi as cell factories: Hype, reality and hope

The extant diversity of fungi and their intraspecies genetic variability offers the scope of finding useful strains producing enzymes, antibiotics or metabolites of scientific or practical importance. Genetic and molecular techniques allow a gene from one organism to be transferred to a safe domesticated fungal species and engineer precise changes in its regulatory DNA sequences to increase expression of the transgene. Cultivation of fungus in industrial-sized fermentors facilitates a desired substance to be produced for commercial use. A few species produce homologous proteins in significant amounts but the expression of heterologous proteins of mammalian origin for practical use is generally low. Among the perceived uses of fungi as cell factories is production of human antibodies. For increasing the secretion of a heterologous protein, an understanding is required of its structure and of the regulatory genes controlling expression of the protein. Furthermore a detailed study of the architecture of the fungal cell wall over period of mycelial growth is required since proteins finally exit through the cell wall.