Biodegradation of poly(3-methoxy-4-hydroxy styrene)

Abstract Poly(3-methoxy-4-hydroxy styrene) (MHS) was prepared as a biodegradable polymer; it offers a simplified model of naturally biodegradable polymers related to softwood lignin, having pendant guaiacyl groups. This polymer was decomposed by microorganisms in soil, and four intermediates were identified in the degradation pathway. Judging from the identified intermediates, vanillic acid seems to be the first biodegradation product of polyMHS in the pathway. The ring cleavage of vanillic acid gives rise to monomethyl ester of β-carboxymuconic acid, discovered as an intermediate in the degradation pathway. Monomethyl ester of β-carboxymuconic acid, which was isolated and characterized, is decomposed to maleic and oxalic acids by microorganisms which are essential for utilization of guaiacyl group. Elucidation of the degradation pathway of polyMHS revealed that the step reactions responsible for the conversion of this compound to maleic and oxalic acids are somewhat similar to the step reactions responsible for the degradation of lignin by microorganisms.