Fermentative Indole Production via Bacterial Tryptophan Synthase Alpha Subunit and Plant Indole-3-Glycerol Phosphate Lyase Enzymes

Ferrer, Lenny; Mindt, M.; Suarez Diez, M.; Jilg, Tatjana; Zagorscak, M.; Lee, Jin-Ho; Gruden, Kristina; Wendisch, Volker F.; Cankar, K.


Indole is produced in nature by diverse organisms and exhibits a characteristic odor described as animal, fecal, andfloral. In addition, it contributes to the flavor in foods, and it is applied in the fragrance and flavor industry. In nature, indole issynthesized either from tryptophan by bacterial tryptophanases (TNAs) or from indole-3-glycerol phosphate (IGP) by plant indole3-glycerol phosphate lyases (IGLs). While it is widely accepted that the tryptophan synthase α-subunit (TSA) has intrinsically low IGL activity in the absence of the tryptophan synthase β-subunit, in this study, we show that Corynebacterium glutamicum TSAfunctions as a bona fide IGL and can support fermentative indole production in strains providing IGP. By bioprospecting additional bacterial TSAs and plant IGLs that function as bona fide IGLs were identified. Capturing indole in an overlay enabled indole production to titers of about 0.7 g L−1 in fermentations using C. glutamicum strains expressing either the endogenous TSA gene orthe IGL gene from wheat.