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Fermentative Production and Direct Extraction of (-)-α-bisabolol in Metabolically Engineered Escherichia Coli

Gui Hwan Han, Seong Keun Kim, Paul Kyung-Seok Yoon, Younghwan Kang, Byoung Su Kim, Yaoyao Fu, Bong Hyun Sung, Heung Chae Jung, Dae-Hee Lee, Seon-Won Kim, Seung-Goo Lee

Microb Cell Fact. 2016 Nov 8;15(1):185.

PMID: 27825357

Abstract:

Background:
(-)-α-Bisabolol, also known as levomenol, is an unsaturated sesquiterpene alcohol that has mainly been used in pharmaceutical and cosmetic products due to its anti-inflammatory and skin-soothing properties. (-)-α-Bisabolol is currently manufactured mainly by steam-distillation of the essential oils extracted from the Brazilian candeia tree that is under threat because its natural habitat is constantly shrinking. Therefore, microbial production of (-)-α-bisabolol plays a key role in the development of its sustainable production from renewable feedstock.
Results:
Here, we created an Escherichia coli strain producing (-)-α-bisabolol at high titer and developed an in situ extraction method of (-)-α-bisabolol, using natural vegetable oils. We expressed a recently identified (-)-α-bisabolol synthase isolated from German chamomile (Matricaria recutita) (titer: 3 mg/L), converted the acetyl-CoA to mevalonate, using the biosynthetic mevalonate pathway (12.8 mg/L), and overexpressed farnesyl diphosphate synthase to efficiently supply the (-)-α-bisabolol precursor farnesyl diphosphate. Combinatorial expression of the exogenous mevalonate pathway and farnesyl diphosphate synthase enabled a dramatic increase in (-)-α-bisabolol production in the shake flask culture (80 mg/L) and 5 L bioreactor culture (342 mg/L) of engineered E. coli harboring (-)-α-bisabolol synthase. Fed-batch fermentation using a 50 L fermenter was conducted after optimizing culture conditions, resulting in efficient (-)-α-bisabolol production with a titer of 9.1 g/L. Moreover, a green, downstream extraction process using vegetable oils was developed for in situ extraction of (-)-α-bisabolol during fermentation and showed high yield recovery (>98%).
Conclusions:
The engineered E. coli strains and economically viable extraction process developed in this study will serve as promising platforms for further development of microbial production of (-)-α-bisabolol at large scale.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP23089261-A Levomenol Levomenol 23089-26-1 Price
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