Amylosucrase-mediated β-carotene encapsulation in amylose microparticles

The β-carotene embedded amylose microparticles (BC-AmMPs) were prepared in one-step by utilizing the unique catalytic activity of amylosucrase from Deinococcus geothermalis (DgAS), which synthesizes linear amylose chains using sucrose as the sole substrate. Synthesized amylose chains self-assembled with β-carotene to form well-defined spherical microparticles with an encapsulation yield of 65%. The BC-AmMPs produced (average diameter ∼8 µm) were bright orange due to the embedded β-carotene, and this was confirmed by Raman analysis. XRD showed BC-AmMPs had a B-type amylose crystal structure with a degree of crystallinity lower than that of AmMPs. This lower crystallinity of AmMP after BC encapsulation was confirmed by DSC analysis. Decreased enthalpy of gelatinization (ΔH_gel ) of BC-AmMP implied that molecular order within the amylose microstructure was influenced by the presence of BC. The stability of BC against environmental stresses, such as UV light and oxidative stress, was significantly enhanced by its encapsulation. The authors propose a new approach to the preparation of an amylose based carrier system for active compounds or expensive food ingredients with poor stabilities during storage or processing. Given that amylose is a safe food material, the devised encapsulation system will find wide range of practical applications in the food industry. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1640-1646, 2017.