Background Functionalization of aliphatic biopolymers such as bacterial polyhydroxyalkanoates (PHA) using biologically active hydrophilic moieties like sugars helps to improve the hydrophilicity and biodegradability of the biomaterial. Results The effects of reaction variables reaction time, temperature, enzyme concentration and substrate ratio on reaction rate and yield in the synthesis of poly(1'-O-3-hydroxyacyl-sucrose) using Candida antarctica lipase B (EC 3.1.1.3) were studied. Using H2O2 as micro-initiator, enzyme-mediated synthesis yielded reaction rate, vapp of 0.076 x 10-5 mol L-1 s-1. The biodegradability of the functionalized polymer was observed to increase by 1.5 fold compared with the non-functionalized material apart from showing better compostability. Increasing the reaction temperature (>50 degrees C), enzyme concentration (>15 g L-1) and reactant ratio (w/w) of sucrose:PHA (>2) did not increase further the rate or yield. The sucrose-functionalized mcl-PHA was characterized with respect to the non-functionalized material. Conclusions Novozym (R) 435 can be used effectively to synthesize poly(1'-O-3-hydroxyacyl sucrose) in micro-aqueous medium bypassing the need for chemo-synthetic steps. The synthesized biomaterials have potential applications in biomedical and industrial niches.(c) 2012 Society of Chemical Industry