Plastics are solid materials where biodegradation happens on the surface. Only the surface is affected by biodegradation while the inner part should not be readily available for biodegradation. Thus, at a laboratory level, the biodegradation rate is expected to be a function of the surface area of the tested sample. The higher the surface area, the higher the biodegradation rate, all other environmental conditions being equal. In order to further explore the role of particle size on biodegradability, plastic pellets of polybutylene sebacate were milled and sieved into different particle sizes, thus obtaining four samples, pellets included, with different specific surface areas (33, 89, 193, and 824 cm²g^-1). The surface areas were assessed through direct measurement (pellets) or a theoretical estimation followed by an image analysis. The different samples were tested for biodegradation in soil for 138 days. The rates calculated with a linear regression in the first part of the biodegradation process were related to the respective total available surface area. The data are well described by a linear regression of the double reciprocal plot (the Lineweaver-Burk approach used in enzymatic kinetics) that enables the estimation of the theoretical maximum biodegradation rate (k_max = 97 mg C_polymer day⁻¹). The k_max can be considered as an estimation of the biodegradation rate at molecular level, when the available surface area is not limiting biodegradation. An additional hypothesis is that the same polymer tested in soils with different microbial loads would display different k_max. The Michaelis constant (K_m), i.e. the surface area at which the reaction rate k is half the maximum rate, is 1122 cm². It is remarkable to notice that if polybutylene sebacate could be tested in a nanopolymeric form, it could very likely satisfy the Organization for Economic Co-operation and Development (OECD) criteria of “ready biodegradability” for chemicals (e.g. 60% biodegradation in a 10-day window within a 28-day test). This is the first time that the biodegradation kinetics of a solid polymer have been estimated by using the Michaelis-Menten approach.

塑料是固体材料，表面会发生生物降解。仅表面会受到生物降解的影响，而内部部件则不易被生物降解。因此，在实验室水平上，预期生物降解速率是被测样品表面积的函数。在所有其他环境条件相同的情况下，表面积越大，生物降解率越高。为了进一步探讨粒径对生物降解性的影响，将聚癸二酸丁二酯塑料颗粒研磨并筛分成不同的粒径，从而得到四个样品，包括颗粒，具有不同的比表面积（33、89、193和824 cm ²克^-1）。通过直接测量（颗粒）或理论估计，然后进行图像分析来评估表面积。测试了不同样品在土壤中的生物降解138天。在生物降解过程的第一部分中通过线性回归计算的速率与各自的总可用表面积相关。数据通过双向倒数图的线性回归（酶动力学中使用的Lineweaver-Burk方法）得到了很好的描述，该线性回归能够估算理论上的最大生物降解率（k _max  = 97 mg C_高分子天^-1）。_最大k当可用表面积不限制生物降解时，可以将其视为在分子水平上生物降解速率的估计。另一个假设是，在具有不同微生物负荷的土壤中测试的相同聚合物会显示出不同的k _max。米氏常数（K _m），即反应速率k为最大速率一半的表面积为1122 cm ²。值得注意的是，如果聚癸二酸丁二酯可以以纳米聚合物形式进行测试，则很可能满足经济合作与发展组织（OECD）的化学品“易生物降解性”标准（例如，在10分钟内60％的生物降解性）。 28天测试中的第3天窗口）。这是首次使用Michaelis-Menten方法估算固体聚合物的生物降解动力学。