4.7 Article

Revealing the link between evolution of electron transfer capacity of humic acid and key enzyme activities during anaerobic digestion

Journal

JOURNAL OF ENVIRONMENTAL MANAGEMENT
Volume 301, Issue -, Pages -

Publisher

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2021.113914

Keywords

Anaerobic process; Anaerobic microbial community; Bio-waste management; Electron accepting; donating capacity; Humic substance

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The study found that the electron transfer capacity (ETC) of HAs increased during anaerobic digestion process at both mesophilic (671-1479 mu mol gHA-1) and thermophilic (774-1506 mu mol gHA-1) conditions. The ETC was positively correlated with bacterial community in hydrolytic and acidogenic phases, but negatively correlated with archaeal community in methanogenic phase. Furthermore, HAs formed under thermophilic conditions had a greater influence on key enzyme activities than those formed under mesophilic conditions.
Humic acid (HA) is an important active compound formed during anaerobic digestion process, with a complex structure and dynamic electron transfer capacity (ETC). However, the mechanisms by which these macromolecular organic compounds dynamically interact with the microbial anaerobic digestion process at different operating temperatures are still unclear. In this study, the link between the evolution of the ETC of HAs and the microbial community under mesophilic and thermophilic conditions was investigated. The results showed an increasing trend in the ETC of HAs in both mesophilic (671-1479 mu mol gHA-1) and thermophilic (774-1506 mu mol gHA-1) anaerobic digestion (AD) until day 25. The ETC was positively correlated with the bacterial community of hydrolytic and acidogenic phases, but negatively correlated with the archaeal community of the methanogenic phase. Furthermore, the relationship between ETC and key enzyme activity was explored using a co-occurrence network analysis. HAs revealed a high potential to promote key enzyme activities during hydrolysis (amylase and protease) and acidification (acetate kinase, butyrate kinase, and phosphotransacetylase) while inhibiting the key enzyme activity in the methanogenic phase during the anaerobic digestion process. Moreover, HAs formed under thermophilic conditions had a greater influence on key enzyme activities than those formed under mesophilic conditions. This study advances our understanding of the mechanisms underlying the influence of HAs on anaerobic digestion performance.

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