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. 2014 Oct 9;45(3):911-8.
doi: 10.1590/s1517-83822014000300021. eCollection 2014.

Production of humic substances through coal-solubilizing bacteria

Nelson Valero  1 , Liliana Gómez  2 , Manuel Pantoja  2 , Ramiro Ramírez  3
Affiliations

Production of humic substances through coal-solubilizing bacteria

Nelson Valero et al. Braz J Microbiol. .

Abstract

In this paper, the production of humic substances (HS) through the bacterial solubilization of low rank coal (LRC) was evaluated. The evaluation was carried out by 19 bacterial strains isolated in microenvironments with high contents of coal wastes. The biotransformed LRC and the HS produced were quantified in vitro in a liquid growth medium. The humic acids (HA) obtained from the most active bacterial strain were characterized via elemental composition (C, H, N, O), IR analyses, and the E4/E6 ratio; they were then compared with the HA extracted chemically using NaOH. There was LRC biotransformation ranged from 25 to 37%, and HS production ranged from 127 to 3100 mg . L(-1). More activity was detected in the isolated strains of Bacillus mycoides, Microbacterium sp, Acinetobacter sp, and Enterobacter aerogenes. The HA produced by B. mycoides had an IR spectrum and an E4/E6 ratio similar to those of the HA extracted with NAOH, but their elemental composition and their degree of aromatic condensation was different. Results suggest that these bacteria can be used to exploit the LRC resulting from coal mining activities and thus produce HS in order to improve the content of humified organic matter in soils.

Keywords: Acinetobacter baumannii; Bacillus mycoides; Enterobacter aerogenes; Microbacterium sp; low rank coal.

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Figures

Figure 1
Figure 1
LRC solubilization through bacteria: a) Expression of LRC solubilization through bacterial activity in a solid growth medium, activity of the CSB34 strain (left), Control (right). b) Evidence of solubilization shown by the production of brown soluble substances. Left: CSB25, Right: Control (growth medium + powdered LRC).
Figure 2
Figure 2
LRC solubilization through bacterial activity in a submerged medium. a) HS production, b) percentage of transformed LRC. n = 3. Treatments with different letters show significant difference (Dunnet, α = 0.05)
Figure 3
Figure 3
Relationship of the final pH of the growth media to the HS production through LRC n = 3. Treatments with different letters show significant difference (Dunnet, α = 0.05).
Figure 4
Figure 4
IR spectra of a) HS obtained from LRC through the activity of Bacillus mycoides 240 (CSB25) and b) extracted from LRC using NaOH 0.5 M.
See this image and copyright information in PMC

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