Data underlying the project: Co-fermentation of Crotonate and Chain Elongation Substrates Towards Mixed Bioplastic/Organic Waste Recovery

Biobased biodegradable plastics, such as polyhydroxyalkanoates (PHA) and polylactic acids (PLA), are increasingly considered as alternatives to fossil-based plastics. While these materials are primarily promoted for biodegradation in industrial composting or anaerobic digestion facilities, their recycling within more closed material loops remains limited. The carboxylate platform is emerging as a promising approach for valorizing organic waste streams, including the microbial recycling of biodegradable plastics. This study explored fermentation conditions to stimulate open-culture bioprocesses using representative biodegradable plastic monomers and typical organic residual substrates processed within the carboxylate platform. 17 batch experiments were conducted with model substrates, including crotonate, ethanol, lactate, and short-chain monocarboxylates. After 28 days of incubation, single crotonate (100 mM) fermentation primarily yielded 105 ± 4 mM acetate and 41 ± 3 mM <em>n</em>-butyrate. Adding 100 mM short-chain monocarboxylates did not inhibit crotonate conversion at an initial pH of 7.0 but extended conversion time. The co-fermentation of 88 ± 10 mM crotonate, 178 ± 20 mM ethanol, and net supplied 39 ± 8 mM acetate under neutral pH conditions produced the highest yield of <em>n</em>-butyrate at 188 ± 17 mM (i.e., 16.5 ± 1.5 g/L), followed by 11 ± 5 mM <em>n</em>-caproate. Co-fermentation of crotonate, ethanol, and lactate was feasible at an initial pH of 5.5, predominantly yielding acetate and <em>n</em>-butyrate. The thermodynamic analysis further supported the bioenergetic feasibility of crotonate conversion and its co-fermentation with ethanol and lactate and showed ample possibilities to improve the fermentation processes. These findings underscore the potential of open-culture fermentation for converting mixed bioplastic and organic waste into carboxylates.

生物基可降解塑料，如聚羟基脂肪酸酯（polyhydroxyalkanoates, PHA）与聚乳酸（polylactic acids, PLA），正日益被视为化石基塑料的替代材料。尽管这类材料的推广应用主要聚焦于工业堆肥或厌氧消化设施中的生物降解场景，但其在更闭合的物质循环体系内的回收利用仍十分有限。羧酸盐平台（carboxylate platform）正逐渐成为有机废弃物流增值转化的极具前景的途径之一，其中也涵盖了可降解塑料的微生物回收过程。本研究选取代表性可降解塑料单体与羧酸盐平台处理的典型有机残余底物，探究了可激发开放式培养生物过程的发酵工艺条件。本研究采用巴豆酸盐（crotonate）、乙醇（ethanol）、乳酸盐（lactate）及短链单羧酸盐（short-chain monocarboxylates）等模型底物开展了17组批次实验。经过28天的培养后，仅添加100 mM巴豆酸盐的发酵体系主要生成了105±4 mM乙酸盐（acetate）与41±3 mM正丁酸盐（n-butyrate）。在初始pH为7.0的条件下，添加100 mM短链单羧酸盐并不会抑制巴豆酸盐的转化，但会延长转化所需的时间。在中性pH条件下，将88±10 mM巴豆酸盐、178±20 mM乙醇与净添加的39±8 mM乙酸盐进行共发酵，可获得最高的正丁酸盐产率：188±17 mM（即16.5±1.5 g/L），其次为11±5 mM正己酸盐（n-caproate）。在初始pH为5.5的条件下，巴豆酸盐、乙醇与乳酸盐的共发酵具有可行性，产物主要为乙酸盐与正丁酸盐。热力学分析进一步证实了巴豆酸盐转化及其与乙醇、乳酸盐共发酵的生物能学可行性，并揭示了优化发酵工艺的充足潜力。上述研究结果凸显了开放式培养发酵技术在将混合生物塑料与有机废弃物转化为羧酸盐方面的应用潜力。