塑膠製成商品已成為當代生活中不可或缺的一部分，全球每年生產的塑膠高達4億噸。隨著環保意識的抬頭，人們開始追求標榜「生物可分解」的塑膠，其中聚乳酸 (Polylactic acid, PLA)塑膠就是一個例子。由於PLA的分解條件特殊，目前處理方式多為焚化。然而，焚燒處理除了意味著能源消耗，還會導致二氧化碳的排放，加劇溫室效應。為了解決廢棄塑膠PLA問題，本研究旨在利用酵素將PLA水解為乳酸 (Lactic acid, LA)，乳酸具有無毒、生物可分解、生物相容性的特性，可為醫療/醫美用途的原料，然而當用作藥物載體時，PLA的高結晶度會導致降解速度緩慢，導致藥物釋放延遲，但若與天然的有機酸—L-蘋果酸 (L-malic acid, L-MA)進行縮合形成聚乳酸-蘋果酸 (Poly (L-lactic acid-co-L-malic acid), PMALA)之共聚物，具有較高的水解效率，且相較於PLA更具疏水的特性，有助於成載藥物，因此PMALA被評價為潛在的抗腫瘤藥物載體、生物製藥和組織再生的載體基質，提高了產品的應用性和價值。
目前約有30%的聚乳酸產品都是通過石化工業提煉而成，以焚化或是掩埋的方式處理對於石化資源而言是浪費的，考量到資源的有限性，勢必得對其進行原物料回收。本研究為塑膠廢棄物問題提供了一個具有潛力的解決方案，透過以酵素Proteinase K水解PLA的方式對LA進行回收，其LA回收效率可達本研究所使用之鹼解效率之60–80%，研究中以廢棄的PLA作為LA來源，並於大氣壓力與溫度80℃下，將其轉化為具有醫療價值的PMALA膠體共聚物，相較於傳統的共聚物的製成需要在真空或減壓且溫度高於110℃以上進行聚合，本研究顯示PMALA能夠在80℃下執行聚合反應，意味著其將有機會依靠地熱系統進行合成，不僅可於相對低溫下運行達到節能的效果外，還替廢棄物PLA進行加值化，更符合現今聯合國所提倡SDGs中的第12項指標「Responsible Consumption and Production」。

Plastic products have become an indispensable part of contemporary life, with global plastic production reaching up to 400 million tons annually. As environmental awareness rises, people are beginning to seek "biodegradable" plastics, with polylactic acid (PLA) being a notable example. Due to the specific conditions required for PLA degradation, incineration is currently the primary disposal method. However, incineration not only consumes energy but also releases carbon dioxide, exacerbating the greenhouse effect. To address the issue of PLA plastic waste, this study aims to use enzymes to hydrolyze PLA into lactic acid (LA). Lactic acid is non-toxic, biodegradable, and biocompatible, making it a suitable material for medical and cosmetic applications. However, when used as a drug carrier, PLA's high crystallinity leads to slow degradation and delayed drug release. By condensing PLA with the natural organic acid L-malic acid (L-MA) to form the copolymer poly (L-lactic acid-co-L-malic acid) (PMALA), the hydrolysis efficiency is increased, and the hydrophobic properties are enhanced compared to PLA. This makes PMALA a potential carrier for anti-tumor drugs, biopharmaceuticals, and tissue regeneration, thereby enhancing the applicability and value of the product. Currently, approximately 30% of polylactic acid (PLA) products are derived from petrochemical processes. Disposing of these products through incineration or landfill is a waste of petrochemical resources. Considering the finite nature of these resources, it is imperative to recycle the raw materials. This study presents a potential solution to the plastic waste problem by using the enzyme Proteinase K to hydrolyze PLA and recover lactic acid (LA), achieving an LA recovery efficiency of 60-80% compared to the alkaline hydrolysis method used in this research. Discarded PLA was utilized as the LA source and converted into the medically valuable PMALA gel copolymer under atmospheric pressure and at 80°C. Unlike traditional copolymer production, which requires polymerization under vacuum or reduced pressure at temperatures above 110°C, this research demonstrates that PMALA can be polymerized at 80°C. This suggests the potential for synthesis using geothermal systems, enabling energy savings by operating at lower temperatures while adding value to waste PLA. This approach aligns with the 12th Sustainable Development Goal (SDG): Responsible Consumption and Production.

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