(688e) Scaling-up a Microbial Process for Converting Dairy Co-Products into Oleochemicals

Oleochemicals are a group of aliphatic compounds derived from fatty acids and lipids. They are categorized based on factors like chain length, terminal reduction state (such as acid, aldehyde, ester, olefin, alcohol, or alkane), and any modifications (e.g., branching, unsaturation, hydroxyl, or cyclopropane groups) to the main chain. These compounds are used in various industrial applications such as lubricants, fuels (e.g., biodiesel), solvents, and as precursors for cosmetics, plasticizers, surfactants, and specialty chemicals. However, current oleochemical sources are limited to specific chain lengths and have considerable ecological impacts. Most oil crops are rich in long-chain compounds (typically 16- or 18-carbon), which do not provide the desirable properties of medium-chain analogs. While oil crops like coconut and palm kernel oil contain some medium chains, their supply is insufficient. The conversion of tropical rainforests to plantations has further decreased their natural availability. In nature, oleochemicals are produced from intermediates in fatty acid biosynthesis. There are enzymes either naturally occurring or engineered to produce medium-chain-length oleochemicals.

At prevailing sugar prices and product yields, the cost of feedstock makes up nearly the entire selling price of oleochemicals. The exceptions are C8 and C10 species, which are less common and sold at 2-3 times the price of long-chain oleochemicals. To address this concern, researchers have been exploring lower-cost renewable feedstocks such as lignocellulosic biomass, algae, glycerol, etc. We hypothesized that dairy wastes, such as whey permeate or acid whey, which contain a mix of fermentable sugars and peptides could also serve as an attractive feedstock for producing high value oleochemicals. Our study highlights the valorization of whey permeate into oleochemicals. We used Escherichia coli MG1655 strains, which was previously engineered to produce oleochemicals. These include NHL17 (produces octanoic acid), TY05 (produces dodecanoic acid) and TAC58 (produces dodecanol). The engineering strategy to create these strains primarily focused on using thioesterases and acyl-ACP reductases to produce specific oleochemical chain lengths. In the current study, we cultivated these strains in flask-batch fermentation. NHL17 produced 390 mg/L octanoic acid, TY05 produced 280 mg/L dodecanoic acid and TAC58 produced 160 mg/L dodecanol. We are currently evaluating these strains’ performances in batch and fed-batch bioreactors using whey permeate. We also plan to supplement the whey permeate to increase cell growth and design metabolic engineering strategies to increase whey permeate utilization and oleochemical production. Since dairy co-products are available at very low cost or can be easily acquired from a dairy plant, we will be evaluating the economics of the bioprocesses using a technoeconomic analysis model. Finally, we will be scaling up the process by using a large bioreactor facility available to us. Overall, our study demonstrates that dairy co-products such as whey permeate can be utilized by engineered E. coli strains for oleochemical production. The experiments planned will help in improving the whole bioprocesses and valorize the dairy co-products into high value chemicals.