The increasing demand for propionic acid (PA) production and its wide
applications in several industries, especially the food industry (as a
preservative and satiety inducer), have led to studies on the low-cost
biosynthesis of this acid. This paper gives an overview of the
biotechnological aspects of PA production and introduces
Propionibacterium as the most popular organism for PA production.
Moreover, all process variables influencing the production yield,
different simple and complex carbon sources, the metabolic pathway of
production, engineered mutants with increased productivity, and
modified tolerance against high concentrations of acid have been
described. Furthermore, possible methods of extraction and analysis of
this organic acid, several applied bioreactors, and different culture
systems and substrates are introduced. It can be concluded that maximum
biomass and PA production may be achieved using metabolically
engineered microorganisms and analyzing the most significant factors
influencing yield. To date, the maximum reported yield for PA
production is 0.973 g\ub7g-1, obtained from Propionibacterium
acidipropionici in a three-electrode amperometric culture system in
medium containing 0.4 mM cobalt sepulchrate. In addition, the best
promising substrate for PA bioproduction may be achieved using glycerol
as a carbon source in an extractive continuous fermentation.
Simultaneous production of PA and vitamin B12 is suggested, and
finally, the limitations of and strategies for competitive microbial
production with respect to chemical process from an economical point of
view are proposed and presented. Finally, some future trends for
bioproduction of PA are suggested