Transcriptional regulation of the Bacillus ohbensis cyclodextrin glucanotransferase gene in B. subtilis

Effect of signal peptides on the secretion of β-cyclodextrin glucanotransferase in Lactococcus lactis NZ9000

Cyclodextrin glucanotransferase (CGTase) is an extracellular enzyme which catalyzes the formation of cyclodextrin from starch. The production of CGTase using lactic acid bacterium is an attractive alternative and safer strategy to produce CGTase. In this study, we report the construction of genetically modified Lactococcus lactis strains harboring plasmids that secrete the Bacillus sp. G1 β-CGTase, with the aid of the signal peptides (SPs) SPK1, USP45 and native SP (NSP). Three constructed vectors, pNZ:NSP:CGT, pNZ:USP:CGT and pNZ:SPK1:CGT, were developed in this study. Each vector harbored a different SP fused to the CGTase. The formation of halo zones on starch plates indicated the production and secretion of β-CGTase by the recombinants. The expression of this enzyme is shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and zymogram analysis. A band size of ∼75 kDa corresponding to β-CGTase is identified in the intracellular and the extracellular environments of the host after medium modification. The replacement of glucose by starch in the medium was shown to induce β-CGTase production in L. lactis. Although β-CGTase production is comparatively low in NZ:SPK1:CGT, the SP SPK1 was shown to have higher secretion efficiency compared to the other SPs used in this study.

Cyclodextrin glucanotransferase: from gene to applications

Cyclodextrin glucanotransferase (CGTase) is an important industrial enzyme which is used to produce cyclodextrins. CGTase genes from more than 30 bacteria have been isolated and several of the enzymes have been identified and biochemically characterized. For a better understanding of the reaction mechanism and function of CGTase, the enzyme has been analyzed at gene level and protein level with regard to its structure and the similarity of different CGTase subgroups. The biological role of the enzyme is proposed based on the genetic and enzymatic analyses. Methods to enhance the production of active CGTase by bacteria are compared. The enzyme can be applied in biotechnology for the production of cyclodextrins and oligosaccharides with novel properties.