Development of Digested Sludge-Assimilating and Biohydrogen-Yielding Microflorae

Digested sludge (DS) is a waste product of anaerobic digestion that is produced during the biodegradation of excess sludge. It cannot be used as a substrate for further biogas production owing to its recalcitrant nature. In the present study, we used a heat treatment technique to convert DABYS micro...

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Bibliographic Details
Published in:Fermentation (Basel) 2023-02, Vol.9 (2), p.175
Main Authors: Hayakawa, Yuhei, Aburai, Nobuhiro, Fujii, Katsuhiko
Format: Article
Language:English
Subjects:
Alternative energy sources
Aluminum
Anaerobic digestion
Bacteria
Biodegradation
Biogas
Carbon dioxide
Cell culture
Cellulase
Cellulose
Chemical properties
Chitinase
Clostridiaceae
digested sludge
Drinking water
Enterobacteriaceae
Enzymes
Fermentation
Heat
Heat treatments
Hydrogen
hydrogen gas
Maximum likelihood method
Methane
Methanogenic bacteria
Microbiota (Symbiotic organisms)
Microflora
Physiological aspects
Production processes
Pseudomonas
Sludge
Soil microorganisms
Thermophilic bacteria
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Summary:Digested sludge (DS) is a waste product of anaerobic digestion that is produced during the biodegradation of excess sludge. It cannot be used as a substrate for further biogas production owing to its recalcitrant nature. In the present study, we used a heat treatment technique to convert DABYS microflora (DABYS = digested sludge-assimilating and biogas-yielding soil microflora), which degraded DS and produced methane gas, to a microflora that could produce hydrogen gas from DS. Heat treatment at 80 and 100 °C inactivated the methanogens that consume hydrogen for methane production but did not affect the thermotolerant bacteria. We developed three microflorae (DABYS-A80, DABYS-A100, and DABYS-80B) to exclusively produce hydrogen gas. They included representatives from the anaerobic eubacterial families Clostridiaceae and Enterobacteriaceae. Pseudomonas sp. was also present in DABYS-A80 and DABYS-A100. It is thought that bacteria in the Enterobacteriaceae family or Pseudomonas genus survive heat treatment because they are embedded in microgranules. Enzymatic analysis suggested that the microflorae hydrolyzed DS using cellulase, chitinase, and protease. Under optimum culture conditions, DABYS-A80, -A100, and B-100 produced gas yields of 8.0, 7.1, and 2.6 mL, respectively, from 1.0 g of dried DS.
ISSN:2311-5637
2311-5637
DOI:10.3390/fermentation9020175