Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2008
Publication Date: 3/1/2009
Citation: Schober, T.J., Bean, S., Wang, D. 2009. Capillary Electrophoresis as a Tool for Evaluating Lactic Acid Production from Sorghum. Cereal Chemistry. 86(2):117-121. Interpretive Summary: Sorghum is an underutilized renewable resource that can be used to produce bio-based products such as ethanol. Recently the production of lactic acid from sorghum was also demonstrated, which can be used to produce a wide range of products. In order to facilitate the production of lactic acid from sorghum, capillary electrophoresis was investigated as a tool to monitor the fermentation process and characterize the fermentation products. It was found that sample preparation, namely dilution of the samples prior to analysis and rinsing the capillaries with HCl were critical steps for using capillary electrophoresis to separate the fermentation broth.
Technical Abstract: Interest in the use of renewable resources for the production of bio-industrial chemicals and fuels is increasing. One industrial chemical that can be produced from renewable resources is lactic acid. Lactic acid is used in the food industry as a flavor compound, preservative, and to acidify products and is also used to produce poly (lactic acid) (PLA), lactate esters, propylene glycol, propanoic acid, acrylic acid and other chemicals. Sorghum is a drought resistant, heat tolerant cereal grown primarily from Kansas to Texas that has been underutilized as a renewable resource. Recent research has demonstrated that in addition to ethanol, lactic acid can be successfully produced from sorghum. In order to rapidly monitor the fermentation process and characterize the fermentation products from this process, capillary electrophoresis was investigated as an analytical tool for use in lactic acid production from sorghum. Initial separations with an acidic phosphate buffer successfully separated organic acid standards, but produced poor reproducibility with fermentation samples. Investigations with model systems designed to mimic the fermentation broth revealed that high levels of calcium carbonate in the fermentation broth were responsible for the poor repeatability. Dilution of the fermentation broth prior to analysis was thus required for successful separations. Post-separation rinses were also investigated and it was found that rinsing the capillary with HCl after each separation provided the best results.