Toxicity and biodegradability of caffeic acid in anaerobic digesting sludge

Abstract

Caffeic acid in waste comes from a variety of industries, and its disposal is likely to increase due to emerging processes such as graphene production and use in healthcare products. The current sustainable option to treat waste caffeic acid and prevent its natural transformation in soil to greenhouse gases, is anaerobic digestion. However, little is known about the toxic and inhibitory effects of caffeic acid on biogas production as well as its ultimate anaerobic biodegradability; or about the reactiveadsorptive processes taking place with caffeic acid in sludge, metabolic intermediates, thermodynamic limitations and the effects on extracellular polymeric substances (EPS). Standard methods revealed that 80% of biogas production (EC 80 ) from a readily digestible biomass was inhibited at 389 mg caffeic acid·g -1 VSS. Up to 52% of caffeic acid was biodegraded. β-oxidation and reductive dehydroxylation were the initial activation reactions transforming caffeic acid into typical polyphenol structural units (protocatechuic acid and 4HBA). Adsorption of caffeic acid (53.3% and 28.6%) to the sludge occurred even at inhibitory concentrations. The EPS structure remained unchanged regardless of the increase in concentration of caffeic acid. Reasonable concentrations of caffeic acid could be co-digested with a similar readily digestible biomass with an expected reduction in biogas production. It is feasible to treat waste caffeic acid by anaerobic digestion and adsorption of its derivates, in order to reduce the contribution to global warming and to protect the environment.

Caffeic acid modulates methane production and rumen fermentation in an opposite way with high‐forage or high‐concentrate substrate in vitro

“…Besides, it is unexpected to observe different populations of methanogens for the two substrates treated by CA. The possible explanation is that supplemental CA in the high‐forage groups overwhelmed cellulolytic bacteria hydrogenation 28 and underwent anaerobic methanogenic decomposition, 32,33 which means that methanogens might benefit from CA, to increase growth of methanogens. As for the high‐concentrate groups, suitable conditions made cellulolytic bacteria rapidly hydrogenate CA 27 to interrupt its benefit to methanogens.…”

Potential Therapeutic Implications of Caffeic Acid in Cancer Signaling: Past, Present, and Future

“…However, successful combinations of potent therapeutic drugs/agents with products may attain the desired conclusion but with lesser toxicity ( Bukowska et al, 2015 ; Das et al, 2018 ). CA has been believed to be a toxic compound of anaerobic wastewater treatment ( Hernandez and Edyvean, 2018 ). However, CA can act differently in terms of digestibility or toxicity in some anaerobic situations—for example, CA undergoes autoxidation in aqueous systems with oxygen draws, resulting in aggregates with adsorptive properties ( Rochelle, 2001 ).…”

Influence of Anaerobic Mesophilic and Thermophilic Digestion on Cytotoxicity of Swine Wastewaters

“…AD is usually characterized by chemical oxygen demand (COD) reduction and biogas production. , Because of the potential presence of the inhibitory digestion substrate(s) on AD, previous work on the toxicity of AD emphasized the inhibitory effects of the specific substrate(s) that could adversely affect operational performance such as methanogenesis and thus the overall AD process. − While these studies provided insights into aspects such as maximizing biogas production during AD, the potential toxic health risks were beyond the scope of these studies. There is a lack of knowledge on the behavior and causes of AD-mediated toxicity .…”