Data underlying the research of Efficient Hydrothermal Pretreatment of Mixed PHA/PLA and Consequent Continuous Anaerobic Fermentation into VFA

Recycling biobased biodegradable plastics such as polyhydroxyalkanoates (PHA) and polylactic acid (PLA) is essential for developing a circular economy. This study presents an integrated strategy that combines batch hydrothermal processing at 150℃ with continuous open-culture fermentation to convert PHA and PLA into C₂-C₆ carboxylates. Co-hydrolysis in a carboxylic acid solution significantly enhanced PHA depolymerization compared to PHA hydrolysis alone. Among various catalytical supplements, PLA addition notably improved PHA hydrolysis, achieving up to 91% dissolution. Throughout fermentation, acetate and <em>n</em>-butyrate were the primary products. In Phase VI, co-fermentation of PHA hydrolysates (~10 g/L 3-hydroxybutyrate) and PLA hydrolysates (5 g/L lactate) yielded acetate (4.4 g/L), <em>n</em>-butyrate (8.0 g/L), and <em>n</em>-caproate (0.3 g/L), while also reducing the need for KOH for pH control. An overall conversion efficiency of 89% from bioplastics to carboxylates was achieved, with a high <em>n</em>-butyrate selectivity of 71%. Supplementing with ethanol (7 g/L) further enhanced chain elongation, increasing <em>n</em>-butyrate concentration to 10.1 g/L, although excess ethanol oxidation was observed. This study demonstrates, for the first time, the successful continuous open-culture fermentation of PHA and PLA hydrolysates into carboxylates. Microbial community analysis identified <em>Clostridium tyrobutyricum</em> as a key species likely responsible for dominant <em>n</em>-butyrate production.

聚羟基脂肪酸酯（PHA）与聚乳酸（PLA）等生物基可降解塑料的回收利用，对于循环经济的发展至关重要。本研究提出一种集成化策略，将150℃下的间歇式水热工艺与连续开放培养发酵相结合，可将PHA与PLA转化为C₂-C₆羧酸盐。相较于单一PHA水解，羧酸溶液中的协同水解显著提升了PHA的解聚效率。在各类催化补加剂中，添加PLA可显著强化PHA水解，最高可实现91%的溶解率。发酵全程以乙酸盐与正丁酸盐为主要产物。第六阶段中，将PHA水解液（约10 g/L的3-羟基丁酸）与PLA水解液（5 g/L乳酸盐）进行协同发酵，生成了乙酸盐（4.4 g/L）、正丁酸盐（8.0 g/L）与正己酸盐（0.3 g/L），同时降低了pH调控所需的KOH用量。本研究实现了生物塑料向羧酸盐的总转化效率达89%，且正丁酸盐的产物选择性高达71%。补加7 g/L乙醇可进一步强化碳链延长过程，将正丁酸盐浓度提升至10.1 g/L，但同时也观察到了过量乙醇氧化的现象。本研究首次证实，可通过连续开放培养发酵将PHA与PLA水解液成功转化为羧酸盐。微生物群落分析显示，酪丁酸梭菌（Clostridium tyrobutyricum）是主导正丁酸盐生成的关键菌种。