S30: The production of propionic acid through sugar fermentation: an industrial perspective on the progress, technical challenges and future outlook

Propionic acid is an important chemical commodity with a rapidly growing demand in a variety of markets ranging from pharmaceuticals to food preservatives.  Currently, the vast majority of propionic acid is manufactured through petrochemical routes which can be tied to increasing prices and volatility due to difficultly in forecasting of demand, varied technological advances and feedstock availability.  A renewable, fermentation based approach to manufacture propionic acid would increase sustainability and enable production in new geographies. As with many fermentation processes, the challenges to developing an economically viable propionic acid process include productivity, titer and product yield. Over five decades of research has shown that propionic acid can be produced by fermentation of Propionibacterium at relatively high amounts.    However, propionic acid itself is highly inhibitory to Propionibacterium limiting fermentations titers to below targeted commercial levels.  Furthermore, product yield is redox limited based on the native biochemical pathways of Propionibacterium.  With the rising cost of fermentation substrates, product yield has become an even bigger factor in developing an economically viable fermentation process.  This talk will summarize the strategies employed at the Dow Chemical Company to overcome the product yield and titer challenges.  A novel medium recipe was developed to improve product yield and reduce manufacturing costs to near economical levels.  Improvements in titer were made through classical organism selection and screening.  A brief economic evaluation of an optimized fermentation process will be presented relative to the incumbent petrochemical based technology.