Lead Process Engineer for project to modify fermentation plant that makes lactic acid for biodegradable polymers. The project included new fermentation air compressors and fermentor modifications. Responsible for coordinating design with the client and developing P&IDs, hydraulic and thermal calculations and equipment specifications.
| Unit operations: Fermentation |
| Products: l(+)-Lactic acid |
| Company: Cargill, Incorporated |
| Location: Blair, Nebraska |
Cargill has a lactic acid fermentation plant at their Blair, Nebraska biorefinery that manufactures enantiomerically pure lactic acid from glucose syrups produced by the corn wet mill. This lactic acid is then extracted and purified, via a lactide intermediate, and then polymerized to make the biodegradable polymer polylactic acid (PLA).
Previously, I had worked on a detailed design project to expand the wet mill and a subsequent preliminary design for the next wet mill expansion while working for Middough Inc. out of their Chicago office. This work led to my work on the modifications of the lactic acid plant.
The first generation lactic acid process used a Lactobacillus bacteria biocatalyst to synthesis lactic acid from glucose. However, this process operated at a pH that required neutralization of the produced lactic acid with a base. The resulting lactate salt then had to be converted back to the free acid. Historically, the production of organic acids by fermentation uses calcium hydroxide as the base to neutralize the acid as it is produced. The broth is then filtered and treated with sulfuric acid which precipitates calcium sulfate (gypsum), leaving the free acid in solution. However, this process produces a large amount of gypsum as a byproduct. Although gypsum is an important industrial product with value as a fertilizer and for use in wallboard, most companies that try to market their fermentation byproduct gypsum find that it has very little value and often they end up with a huge pile of gypsum behind the plant.
Faced with these same issues, Cargill researches set out to find a new microorganism that would tolerate a lower fermentation pH and thus reduce or eliminate the need for addition of base and the formation of the lactate salt. Eventually, they identified a suitable yeast host and developed it into their CB1 biocatalyst. This project designed the modifications to the fermentation plant needed to produce lactic acid using the new CB1 biocatalyst.
This same CB1 yeast was also licensed by BioAmber and eventually used in their Sarnia, Ontario succinic acid fermentation plant.