Enzymatic synthesis of galactosyl lactic ethyl ester and its polymer for use as biomaterials

Lactate-based chemicals and polymers including poly(lactic acid) (PLA) are highly valuable materials for biomedical, food and general-purpose applications. Chemical synthesis, albeit the high reaction velocities achieved with it, often leaves chemical residues that are subject to health and safety concerns. Alternative biosynthesis is preferred in order to overcome these problems. Herein we report a novel enzymatic synthesis for the preparation of β-d-galactosyl-l-lactic acid ethyl ester (GLAEE). Such a product, which may find applications in food and personal care products, is generally difficult to synthesize via traditional chemical routes because the reactions have to be highly selective due to the multiple hydroxyl groups of sugars. We further explore the enzymatic polymerization of GLAEE to form a unique biopolymer, poly(β-d-galactoside-co-l-lactic acid) (PGLA). Novozyme 435® was found efficient in catalyzing the polymerization reaction in acetone with a conversion yield of 60% within 100 h. The molecular weight of the polymer product ranged from about 800–2000 as analyzed by using ESI-MS. It is expected that a variety of sugar-hydroxyl acids copolymers can be prepared through the same approach and a new class of biomaterials can thus be developed.