Many of the commercial production processes for organic acids are excellent examples
of fungal biotechnology. However, unlike penicillin, the organic acids have had a less visible
impact on human well-being. Indeed, organic acid fermentations are often not even
identified as fungal bioprocesses, having been overshadowed by the successful deployment
of the -lactam processes. Yet, in terms of productivity, fungal organic acid processes
may be the best examples of all. For example, commercial processes using Aspergillus
niger in aerated stirred-tank-reactors can convert glucose to citric acid with greater than
80% efficiency and at final concentrations in hundreds of grams per liter. Surprisingly, this
phenomenal productivity has been the object of relatively few research programs. Perhaps
a greater understanding of this extraordinary capacity of filamentous fungi to produce
organic acids in high concentrations will allow greater exploitation of these organisms via
application of new knowledge in this era of genomics-based biotechnology.