The synthesis of biodegradable polymers with high temperature sensitivity based on natural materials to replace the notorious non-biodegradable poly(NIPAAm) remains a highly challenging task. It requires an optimal balance between hydrophilic groups, ensuring aqueous solubility, and hydrophobic groups that facilitate thermal response. In particular close to the human body temperature. We synthesized biodegradable pullulan microspheres with temperature sensitivity, comparable to poly(NIPAAm) microgels, by first succinylating pullulan to introduce carboxylic groups, then partially amidating these groups with isopropylamine. Preliminary Molecular Dynamics simulations guided the determination of suitable substitution levels necessary for achieving desired thermosensitivity. The resulting microgels exhibit rapid swelling/deswelling kinetics (in a scale of seconds), with a remarkable collapse to nearly the original dry volume. Importantly, their transition temperature can be finely adjusted through progressive ionization of residual carboxyl groups. Enzymatic biodegradation studies indicated a slow degradation rate.