Abstract

Bioconversion of medium-chain carboxylic acids (MCCAs) from biowastes through anaerobic mixed-culture fermentation is undergoing a revolution in terms of mitigating the lower fossil fuels requirement and increasing biowaste treatment capacity. Benefiting from hydrophobicity and high energy density of MCCA, this high-valuable biofuel exhibits easier separation and wider application than traditional volatile fatty acid products. The biggest bottleneck for efficiently and simultaneously producing MCCAs by mixed-culture fermentation is complicated or even entangled microbial interaction. Therefore, this review aimed to supply guidelines to understand and steer these microbiomes toward the controllable ones. The metabolic pathway of chain elongation and associated cooperating and competing pathways were firstly discussed to understand the primary microbial interaction in mixed-culture fermentation. In an attempt to inspect the overall performance of mixed-culture CE reactor, the typical microbial community and its variation influenced by reactor parameters were also identified. The methods of in-line extraction of MCCAs for relieving toxicity inhibition on microbiome were also summarized regarding the difficulties lied in continuous MCCAs production. Finally, the future research directions of MCCAs production via mixed-culture fermentation would be proposed to help steer these novel bioproduction processes toward full-scale applications.

摘要

通过厌氧混合培养发酵从生物废物中生物转化中链羧酸 (MCCA) 在降低化石燃料需求和提高生物废物处理能力方面正在经历一场革命。受益于 MCCA 的疏水性和高能量密度，这种高价值的生物燃料比传统的挥发性脂肪酸产品更容易分离和更广泛的应用。混合培养发酵高效同时生产MCCA的最大瓶颈是复杂甚至纠缠的微生物相互作用。因此，本综述旨在为理解这些微生物组并将其引导至可控微生物组提供指导。首先讨论了链延长的代谢途径以及相关的合作和竞争途径，以了解混合培养发酵中的主要微生物相互作用。为了检查混合培养 CE 反应器的整体性能，还确定了典型的微生物群落及其受反应器参数影响的变化。还总结了在线提取 MCCAs 以减轻对微生物组的毒性抑制的方法，以解决连续生产 MCCAs 的困难。最后，将提出通过混合培养发酵生产 MCCAs 的未来研究方向，以帮助引导这些新的生物生产工艺走向全面应用。为了检查混合培养 CE 反应器的整体性能，还确定了典型的微生物群落及其受反应器参数影响的变化。还总结了在线提取 MCCAs 以减轻对微生物组的毒性抑制的方法，以解决连续生产 MCCAs 的困难。最后，将提出通过混合培养发酵生产 MCCAs 的未来研究方向，以帮助引导这些新的生物生产工艺走向全面应用。为了检查混合培养 CE 反应器的整体性能，还确定了典型的微生物群落及其受反应器参数影响的变化。还总结了在线提取 MCCAs 以减轻对微生物组的毒性抑制的方法，以解决连续生产 MCCAs 的困难。最后，将提出通过混合培养发酵生产 MCCAs 的未来研究方向，以帮助引导这些新的生物生产工艺走向全面应用。