Fermentative production and direct extraction of (-)-α-bisabolol in metabolically engineered Escherichia coli

• Published in: Microbial cell factories Vol. 15; no. 1; p. 185
• Main Authors: Han, Gui Hwan, Kim, Seong Keun, Yoon, Paul Kyung-Seok, Kang, Younghwan, Kim, Byoung Su, Fu, Yaoyao, Sung, Bong Hyun, Jung, Heung Chae, Lee, Dae-Hee, Kim, Seon-Won, Lee, Seung-Goo
• Format: Journal Article
• Language: English
• Published: England BioMed Central 08.11.2016
• Subjects: Vegetable oils; (−)-α-Bisabolol synthase; Escherichia coli; (−)-α-Bisabolol; Mevalonate pathway; Farnesyl diphosphate synthase; In situ extraction
• ISSN: 1475-2859; 1475-2859
• DOI: 10.1186/s12934-016-0588-2

(-)-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. 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%). 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.