Product emulsification in multiphase fermentations

Abstract

Sesquiterpenes are a versatile group of 15-carbon molecules, traditionally extracted from plants for diverse applications ranging from fuels to fine chemicals and pharmaceuticals. Scarcity of natural resources and emergence of new applications have encouraged the development of sustainable solutions to produce sesquiterpenes. The recent development of engineered microbial strains able to produce and secrete sesquiterpenes reaching fermentation titres in the order of g per L, is a promising alternative to produce diesel-like biofuels from renewable biomass sources, like sugar cane bagasse. The most attractive aspect of sesquiterpene fermentations is that the extracellular product readily forms an oil phase separated from the aqueous fermentation broth in the reactor. The difference of densities between the aqueous broth and the light product phase opens the opportunity of integrating cost-efficient separation techniques (e.g. gravity separation, hydro-cyclones) with the reactor. This scenario could contribute to significantly lowering equipment and utility costs as well as reducing cost of raw materials by allowing for cell recycling. The scale-up of sesquiterpene fermentations has unveiled processing challenges that were not prominently present at laboratory scale.