Filamentous fungi form multi-cellular structures known as
mycelia. These are important organisms because they produce proteins,
metabolites and pharmaceutical compounds that have an
increasing demand worldwide. For example, the global production
of citric acid, an essential component of a great number of foods
and beverages, is based on fermentation of the fungus Aspergillus
niger (A. niger). This industry reaches 1.75 million tons annually
with an annual growth of up to 4.0% [1]. Species of the genera
Aspergillus generate large amounts of important enzymes [2–4].
Because of this, the secretion system of A. niger has been studied
in detail to generate strains that produce high yields of extracellular
proteins; however, most of these strains were generated by
mutagenic agents like ultraviolet light or chemicals [5,6],
which commonly cause unwanted changes in the sequences of
deoxyribonucleic acid (DNA) and in many cases the nature of the
mutation is not known