Production of cyclodextrins, a novel carbohydrate, in the tubers of transgenic potato plants

Abstract

Cyclodextrins (CDs) are cyclic oligosaccharides containing six (alpha), seven (beta), or eight (gamma) glucose molecules, respectively. The cyclodextrin glycosyltransferases (CGT), which produce CDs from starch, are found only in bacteria and are used in batch fermentors with hydrolyzed starch to produce CDs commercially. Using a CGT gene from Klebsiella, we attempted to engineer the tubers of developing potatoes to produce these novel, high-value carbohydrates. A chimeric gene, consisting of (1) the patatin promoter for tuber-specific expression, (2) the small subunit of ribulose bisphosphate carboxylase (SSU) transit peptide for plastid targeting, (3) the CGT structural gene from Klebsiella and (4) the nopaline synthase 3' region, was introduced into potatoes. Both alpha and beta CDs were produced in tubers of transgenic potatoes at levels corresponding to 0.001-0.01% of the starch being converted to CDs.