Techno-Economic Assessment of a Bioprocess for Long-Chain Dicarboxylic Acid Production from Vegetable Oils: A Case Study for Distillers Corn Oil

This study analyzes the techno-economic feasibility of a bioprocess for production of unsaturated long-chain dicarboxylic acids (LCDCAs) from distillers corn oil (DCO). Currently, there are a limited number of LCDCA products readily available, with dodecanedioic acid and brassylic acid (C12 and C13 LCDCAs) being the most widely marketed products of this type. This process could allow for the expansion of the LCDCA and specialty polymer market by introducing longer LCDCAs which can further tune polymer properties, fill performance gaps, and offer unique properties such as crosslinking and adding additional functional groups. A conceptual design of the process was developed based on conversion of the triglycerides in DCO to fatty acid methyl esters (FAMEs), followed by bioconversion of FAMEs to LCDCAs. The upstream portion starts with a transesterification reactor where DCO is fed into a batch reactor with excess methanol and sodium hydroxide catalyst. Then, the effluent consists of FAMEs, glycerol, and excess methanol. The effluent is distilled to yield FAMEs and glycerol for fermentation and the excess methanol is recycled back into the transesterification reactor. The fermentation section of the process involves multiple bioreactors which utilize the Candida viswanathii yeast strain to convert the FAMEs to LCDCAs. The downstream portion of the process contains multiple separation and filtration units which remove any impurities from the fermentation and upstream portions of the process. The resulting product is then distilled twice using vacuum distillation to recycle any unreacted FAMEs into the fermentation portion of the process and to separate the 98.0% pure C-18 LCDCA product from the 48.5% pure C-16 LCDCA product. Sensitivity analysis was employed to estimate the minimum selling price for the LCDCA product with respect to variation in feedstock cost and fermentation time. Within the historic range of DCO prices, feasible scenarios exist, yielding a selling price of LCDCA less than $5.50/kg, competitive with the price of available specialty dicarboxylic acids such as sebacic and dodecanedioic acid. Alternative feedstock and processing scenarios were also explored, as the process could be adapted to utilize other vegetable oils or available fatty acids such as oleic acid and include unit operations such as hydrogenation reactors to yield a fully saturated LCDCA product.