Data underlying the research of Mesophilic Fermentation Explorations for Anaerobic Carboxylates Production from Commercial Bioplastic Products: PHA-based ‘Happy Cups’ & PLA-based Lids

Biodegradable plastics such as polyhydroxyalkanoates (PHA) and polylactic acid (PLA) are increasingly applied in commercial products, but their end-of-life (EoL) processing remains inefficient in terms of carbon and energy recovery. Carboxylates, such as acetate and <em>n</em>-butyrate, are valuable platform chemicals that can serve as precursors for bioplastics, biofuels, and other biobased products. Producing carboxylates from biodegradable plastics offers a promising strategy to recover carbon and support circular EoL management beyond conventional options like composting or incineration. This study presents mesophilic open-culture fermentation strategies to convert commercial PHA and PLA raw materials and/or products into carboxylates. A sequential bioprocess was developed using a gas-lift anaerobic filter bioreactor, initiating in Phase I with batch fermentation of hydrolysates derived from hydrothermally pretreated PHA (10 g/L) and PLA (1.4 g/L) pellets. In Phase II, continuous operation produced 6.6 g/L acetate and 4.8 g/L <em>n</em>-butyrate from the same hydrolysates source. During Phase III, additional shredded commercial bioplastic products (PHA-based cups and PLA-based lids) were filled to co-ferment with hydrolysates, which further increased acetate and <em>n</em>-butyrate yields to 7.2 g/L and 5.5 g/L, respectively. In subsequent phases, hydrolysates feeding was stopped, and only the remaining solid bioplastics were used. The hydraulic retention time was extended from 2 to 18 days in Phase V. Overall, 35% of the PHA-based cups were converted into carboxylates, while PLA-based lids showed negligible degradation. Residual plastics were partially fragmented into microplastics. Microbial community analysis revealed that <em>Clostridium tyrobutyricum</em> likely played a key role in the hydrolysates fermentation of PHA and PLA pellets, while a broader microbial consortium contributed to solid bioplastic conversion.

聚羟基脂肪酸酯（polyhydroxyalkanoates, PHA）与聚乳酸（polylactic acid, PLA）等生物塑料在商用产品中的应用日益广泛，但其生命周期末端（end-of-life, EoL）处理在碳与能量回收方面仍存在效率短板。乙酸盐（acetate）、正丁酸盐（n-butyrate）等羧酸盐类是极具价值的平台化学品，可作为生物塑料、生物燃料及其他生物基产品的前体物质。从生物塑料制备羧酸盐，为突破堆肥、焚烧等传统处理方式的局限，实现碳回收与循环型生命周期末端管理提供了极具前景的策略。本研究提出了中温开放式培养发酵策略，用于将商用PHA与PLA原料及/或成品转化为羧酸盐。研究开发了一套序贯生物工艺，采用气升式厌氧滤池生物反应器（gas-lift anaerobic filter bioreactor）：第一阶段以水热预处理后的PHA（10 g/L）与PLA（1.4 g/L）颗粒水解液开展分批发酵；第二阶段以相同水解液为底物进行连续运行，最终产出6.6 g/L乙酸盐与4.8 g/L正丁酸盐；第三阶段加入粉碎后的商用生物塑料成品（PHA基杯具与PLA基杯盖）与水解液共发酵，将乙酸盐与正丁酸盐的产率分别提升至7.2 g/L与5.5 g/L。后续阶段停止添加水解液，仅以剩余固态生物塑料作为底物。第五阶段将水力停留时间（hydraulic retention time）从2天延长至18天。整体而言，35%的PHA基杯具被转化为羧酸盐，而PLA基杯盖的降解程度可忽略不计；残留塑料部分碎裂为微塑料（microplastics）。微生物群落分析（microbial community analysis）结果显示，酪丁酸梭菌（Clostridium tyrobutyricum）可能在PHA与PLA颗粒水解液发酵过程中发挥关键作用，而固态生物塑料的转化则依赖于更为广泛的微生物菌群联合体。