PLASTICIZATION OF BACTERIAL POLYESTER BY THE ADDITION OF ACYLGLYCEROLS AND ITS ENZYMATIC DEGRADABILITY

The addition of acylglycerols into bacterial poly(3-hydroxybutyrate) (PHB) resulted in a decrease in Young's modulus and the tensile strength of PHB. The triacylglycerols with short alkyl chains (such as glycerol triacetate, glycerol tripropionate, and glycerol tributyrate) and the monoacylglycerols with a long alkyl chain (such as glycerol monostearate) showed good compatibility with PHB and functioned as plasticizers for PHB. Among the acylglycerols, glycerol triacetate (GTA) was the best plasticizer for PHB. When GTA was added by 30 wt% to PHB, Young's modulus of PHB decreased from 1620 MPa to 280 MPa, while the elongation at break increased from 5% to 130%. The solid-state (CP/MAS and PST/MAS) C-13 NMR spectra showed that the mobility of PHB chains in amorphous regions was increased by the addition of GTA. The enzymatic degradation of the PHB film containing acylglycerols has been studied at 37-degrees-C in the aqueous solution (pH 7.4) of an extracellular PHB depolymerase (from Alcaligenes faecalis T1) or lipase (from Phycomyces nitens). The rate of enzymatic degradation was influenced by the structure of acylglycerols.