Integration of oil recovery and fermentation of sesquiterpenes

Extracellular production of sesquiterpenes (C₁₅H₂₄) via fermentation using modified microorganisms is a promising alternative to overcome the problems of traditional processes based on extraction from plants (e.g., availability of raw material, low yields). Microbial strains are available which can produce sufficient amount of sesquiterpene [4,5]. However, surface-active components (SACs) present in the fermentation broth interfere with the oil recovery [2]. The produced sesquiterpene forms a stable emulsion, and its recovery requires then the use of costly demulsifiers and several centrifugation steps [3], making the process less competitive, especially in the field of fuels.

It has been proposed that coalescence of hydrocarbon droplets into a continuous phase can be achieved through a gas bubble induced recovery method [1]. This method does not require additives, and hence it might be suited for direct product removal during fermentation.  In this work, fed batch fermentations were performed in a 2 L fermentor connected to a 500 mL aerated column. Cell viability, concentration of SACs and oil recovery were measured at different residence times and aeration rates in the column. Although cell viability and fermentation performance were not affected, SACs such as extracellular proteins increased in the integrated system, leading to variations in emulsification and oil recovery. It was concluded that cell stress responses have to be considered when designing a separation device for integrated oil recovery.

[1]Cuellar Soares et al.(2015) WO2015/130167(A1)

[2]Heeres et al.(2014) TrendsBiotechnol.32(4):221-229

[3]Tabur et al.(2012) US20120040396

[4]Tsuruta et al.(2009) PLoS ONE 4(2):e4489

[5]Westfall et al.(2012) PNAS 109(3):E111-E118