A Rapid Analytical Method for Quantification of Volatile Organic Acids in Fermentation Broth

Short chain fatty acids or volatile fatty acids (VFAs) (i.e. acetic, butyric, propionic, lactic, succinic, itaconic) are common products of biochemical conversion of biomass into useful chemicals. This group of compounds is considered to be one of the top chemical platforms for the production of high value products from renewable sources. Liquid chromatography is the commonly used method for analyzing VFAs in aqueous medium. However, the presence of microbial cells in the medium adds to the sample work-up prior to analysis. The sample work-up if not done correctly could cause clogging which could cause process downtime as well as reduce column lifespan. Thus, an alternative procedure was proposed in this study.  

A simple and rapid analytical method for quantification of  VFAs in fermentation broth was  developed using solid phase microextraction (SPME) coupled to gas chromatography (GC). The rapid determination is  useful in monitoring fermentative production of VFAs  and/or their utilization to produce  chemicals such as microbial lipids. Using the proposed analytical method, acids including  acetic, propionic, butyric,  valeric, citric, lactic, itaconic, and succininc were separated and quantitated.  Detection limits and recovery  for these organic acids in  various fermentation broths using different waste substrates  were determined. This method allows fast determination with little to no sample preparation requirement, therefore allowing fast turnaround times to conduct kinetic rates for fermentative VFA production and utilization..