Publications
Engineering Escherichia coli for the production of terpene mixture enriched in caryophyllene and caryophyllene alcohol as potential aviation fuel compounds
Caryophyllene, a natural bicyclical sesquiterpene compound, and its alcohol are widely used in citrus flavors, spice blends, soaps, detergents, creams, lotions as well as in various food and beverage products. Recent studies have revealed that beta-caryophyllene exhibits a wide range of biological activities including anti-inflammatory, anti-cancer, anti-genotoxic capacity, neuroprotection…etc. Besides the biological activities, recent studies suggested blending of hydrogenated sesquiterpanes (carophyllanes, in particular, which have a moderate cetane number and only moderately high viscosity) with synthetic branched paraffins to raise cetane and reduce viscosity. Therefore, caryophyllene and its isomers have been deemed to be among the top three most promising jet fuel compounds with increased energy density. In this study, caryophyllene, caryolan-1-ol, and other terpenes were significantly produced by heterologous expressing a mevalonate pathway with a geranyl pyrophosphate synthase (GPPS), a caryophyllene synthase, and a caryolan-1-ol synthase into an E.coli strain. With the optimization of metabolic flux through four different pathway constructs and fermentation parameters, the engineered strains yielded 448.7mg/L total terpene including 405.9 mg/L sesquiterpene, 42.7 mg/L monoterpene,100 mg/L of caryophyllene, 10 mg/L of caryolan-1-ol. Furthermore, an algal hydrolysate was used by the engineered strain as solo carbon source for the production of caryophyllene and other terpene compounds. Under optimal fermentation conditions, the total terpene, sesquiterpene, and caryophyllene reached 360.3-, 322.5-, and 75.2 mg/L, respectively. The highest yields achieved were 47.9 mg total terpene/ g algae and 10.0 mg caryophyllene/ g algae, respectively, which is about ten times higher than essential oil yield extracted from plant tissue. This study was the first report of caryophyllene production using algae biomass as feedstock. The study provides a sustainable alternative for caryophyllene and its alcohol production as potential candidates for next generation aviation fuels and pharmaceutical applications.