Humin Assists Reductive Acetogenesis in Absence of Other External Electron Donor

Mahasweta Laskar, Takuya Kasai, Takanori Awata and Arata Katayama
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Mahasweta Laskar: Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
Takuya Kasai: Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
Takanori Awata: National Institute for Land and Infrastructure Management, Tsukuba 305-0804, Japan
Arata Katayama: Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan

IJERPH, 2020, vol. 17, issue 12, 1-13

Abstract: The utilization of extracellular electron transfer by microorganism is highly engaging for remediation of toxic pollutants under “energy-starved” conditions. Humin, an organo-mineral complex of soil, has been instrumental as an external electron mediator for suitable electron donors in the remediative works of reductive dehalogenation, denitrification, and so forth. Here, we report, for the first time, that humin assists microbial acetogenesis as the extracellular electron donor using the electron acceptor CO 2 . Humin was obtained from Kamajima paddy soil, Japan. The anaerobic acetogenic consortium in mineral medium containing CO 2 / HCO 3 − as the inorganic carbon source used suspended humin as the energy source under mesophilic dark conditions. Retardation of acetogenesis under the CO 2 -deficient conditions demonstrated that humin did not function as the organic carbon source but as electron donor in the CO 2 -reducing acetogenesis. The consortium with humin also achieved anaerobic dechlorination with limited methanogenic activity. Total electron-donating capacity of humin was estimated at about 87 µeeq/g-humin. The metagenomic sequencing of 16S rRNA genes showed the predominance of Firmicutes (71.8 ± 2.5%) in the consortium, and Lachno spiraceae and Ruminococcaceae were considered as the CO 2 -reducing acetogens in the consortium. Thus, microbial fixation of CO 2 using humin introduces new insight to the holistic approach for sustainable treatment of contaminants in environment.

Keywords: humin; reductive acetogenesis; CO 2 reduction; autotrophic; dechlorination; methanogenesis (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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