Fabrication‐Dependent Enzymatic Degradation of Poly(Lactic Acid) Microplastics

While microplastics (MPs) derived from most petroleum‐based plastics persist in the environment, their counterparts made of bioplastics such as poly(lactic acid) (PLA) offer the potential for biodegradation. However, their actual environmental fate is not solely dictated by degradation conditions, but it is also critically influenced by their processing and fabrication history, which governs their physicochemical properties. This study specifically investigates how the fabrication method of PLA MPs controls their enzymatic degradation. MPs produced through different manufacturing protocols were subjected to degradation by a commercial lipase enzyme from Aspergillus oryzae . After 28 days of enzymatic hydrolysis at pH 8.0, noticeable changes in the surface morphology of MPs were observed due to the emergence of pores ranging from hundreds of nanometers to less than two micrometers. Detailed characterizations reveal that the MPs’ fabrication pathway is a key determinant of degradation performance. Despite comparable particle size, MPs produced via different methods exhibited distinct degradation responses, as evidenced by variations in carbonyl index (CI, up to 12.0%) and crystallinity (up to c.a. 43.0%) and a decrease of the polymer’s molecular weight of up to c.a. 17.5% depending on the sample type. This study confirms the capability of the lipase enzyme to degrade PLA and underscores that the degradation performance is governed by the formation process of the polymeric particles. This highlights a critical and often overlooked aspect in MP and nanoplastic (NP) research: particles with identical chemical composition but different formation histories can exhibit markedly different biodegradation behaviors. Therefore, careful consideration of the fabrication route is essential for the accurate interpretation and comparison of biodegradation studies.