A New Approach to Assess the Effect of Various Humic Compounds on the Metabolic Activity of Cells Participating in Methanogenesis

Nikolay Stepanov,Olga Senko,Elena Efremenko,Irina Perminova

doi:10.3390/su11113158

Abstract

The possible use of the concentration of intracellular adenosine triphosphate (ATP) as a parameter enabling quick and adequate evaluation of the metabolic activity of methanogenic cells was demonstrated in the work. This approach was used to analyze the effect of introducing potassium humate and fulvic acids (1–10 g/L) into media with four different methanogenic consortia producing biogas. The ATP concentration was analyzed by the bioluminescent luciferin–luciferase method at the beginning and end of the process. During the entire process, the biogas composition, biogas efficiency, and the kinetics of methanogenesis in the presence of humic compounds were determined. The increase in the concentration of potassium humate led to a decrease in the overall energy status of the cells and reduced methanogenesis efficiency. However, fulvic acids introduced into the media stimulated methanogenesis in half of the tested consortia, which was accompanied by an increase in ATP concentration in cell samples. So, a positive correlation between the metabolic activity of cells in biogas formation and the concentration of ATP was observed. ATP concentration control appears to be an attractive tool for finding compounds that suppress methanogenesis in landfills.

Highlights

Landfills of solid household waste pose a serious long-term risk to the environment and public health
Four anaerobic consortia were used: I—natural anaerobic consortium isolated from the Kashira landfill (Kashira, Russia); II—natural anaerobic consortium taken from an inactive landfill (Pokrov, Russia, thermophile, 55 ◦C); III—anaerobic consortium obtained from a digester which treated cattle waste (Dmitrov, Russia, 37 ◦C); IV—anaerobic consortium obtained from the wastewater of a food plant (Kashira, Russia, 37 ◦C)
When varying the concentration and type of the natural humic compounds (HCs) (PH or fulvic acids (FA)) introduced into the medium, it was found that the presence of potassium humate (PH) in contact with methanogenic consortia led to a decrease in the overall energy status of the cells

Summary

Introduction

Landfills of solid household waste pose a serious long-term risk to the environment and public health. Uncontrolled emission of landfill gas can cause fires and explosions, since the biochemical processes occurring inside the landfill lead to an increase in the temperature and to the spontaneous combustion of waste [2,3]. For this reason, in many developed countries, special procedures are used to minimize landfill gas emission. Methods based on the oxidation of methane by coating landfills with a layer of compost containing methanotrophic bacteria are used [5,6] Such systems rapidly decompose, and as a result, methane synthesis increases again [6]. Under real conditions, it is impossible to completely suppress the process of methane formation; it is possible to solve the problem by decreasing the rate of gas emission and changing the composition of the emitted gas by reducing the methane content therein

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