One-Step Enzymatic Synthesis of Blue Pigments from Geniposide for Fabric Dyeing

In this study, we describe a one-step chemoenzymatic reaction for the production of natural blue pigments, in which the geniposide from Gardenia extracts is transformed by glycosidases to genipin. Genipin is then allowed to react with amino acids, thereby generating a natural blue pigment. The ${\beta}-glycosidases$, most notably Isolase (a variant of ${\beta}-glucanase$), recombinant ${\beta}-glycosidases$, Cellulase T, and amylases, were shown to hydrolyze geniposide to produce the desired pigments, whereas the ${\alpha}-glycosidases$ did not. Among the 20 tested amino acids, glycine and tyrosine were associated with the highest dye production yields. The optimal molar ratio of geniposide to glycine, two reactants relevant to pigment production, was unity The natural blue pigments produced in this study were used to dye cotton, silk, and wool. The color yields of the pigments were determined to be significantly higher than those of other natural dyes. Furthermore, the color fastness properties of these dyes were fairly good, even in the absence of mordant.