Effect of Red Clay on Diesel Bioremediation and Soil Bacterial Community

Abstract

Red clay is a type of soil, the red color of which results from the presence of iron oxide. It is considered an eco-friendly material, with many industrial, cosmetic, and architectural uses. A patented method was applied to red clay in order to change its chemical composition and mineral bioavailability. The resulting product was designated processed red clay. This study evaluates the novel use of red clay and processed red clay as biostimulation agents in diesel-contaminated soils. Diesel biodegradation was enhanced in the presence of red clay and processed red clay by 4.9- and 6.7-fold, respectively, and the number of culturable bacterial cells was correlated with the amount of diesel biodegradation. The growth of Acinetobacter oleivorans DR1, Pseudomonas putida KT2440, and Cupriavidus necator was promoted by both types of red clays. Culture-independent community analysis determined via barcoded pyrosequencing indicated that Nocardioidaceae, Xanthomonadaceae, Pseudomonadaceae, and Caulobacteraceae were enriched by diesel contamination. Bacterial strain isolation from naphthalene- and liquid paraffin-amended media was affiliated with enriched taxa based on 16S rRNA gene sequence identity. We suggest that the biostimulating mechanism of red clay and processed red clay is able to support bacterial growth without apparent selection for specific bacterial species.

Molecular Mechanisms of Enhanced Bacterial Growth on Hexadecane with Red Clay

“…In particular, at hydrocarbon-contaminated sites, adjustment of the C/N/P ratio is important for efficient bioremediation because of the excess amount of carbon [31]. In this context, application of red clay is a novel strategy for enhancing bioremediation of hydrocarbon-contaminated sites because red clay contains only inorganic mineral compounds such as SiO 2 , Al 2 O 3 , and Fe 2 O 3 [13]. Previously, we found that the growth of A. oleivorans DR1, P. putida, and Ralstonia eutropha H16 on succinate was enhanced by red clay, and the number of culturable cells from a diesel-contaminated soil microcosm was also higher when red clay was added [13].…”

“…In this context, application of red clay is a novel strategy for enhancing bioremediation of hydrocarbon-contaminated sites because red clay contains only inorganic mineral compounds such as SiO 2 , Al 2 O 3 , and Fe 2 O 3 [13]. Previously, we found that the growth of A. oleivorans DR1, P. putida, and Ralstonia eutropha H16 on succinate was enhanced by red clay, and the number of culturable cells from a diesel-contaminated soil microcosm was also higher when red clay was added [13]. Based on those data, we speculated that red clay enhanced the degradation of diesel by promoting bacterial growth, but further investigation was not undertaken at that time.…”

“…To enumerate the number of cells, culture media were serially diluted and spread on a nutrient agar plate. Red clay was added to hexadecane-amended M9 medium at 0.1 % (v/v) because it was found to promote the growth of strain DR1 and other species of soil bacteria as well as diesel biodegradation [13].…”

“…Previously, our group used processed red clay as a biostimulant for bioremediation of diesel-contaminated soil [13]. Processed red clay is a material produced by a patented method (Republic of Korea patents 1008247350000 and 1008860820000) that removes impurities other than minerals and enhances soil mineral availability.…”

Economical synthesis of complex silicon fertilizer by unique technology using loess

“…The supply of soluble materials such as silicon and minerals in LPM can increase the extent of microorganisms and enzyme activity in cultivated soil, and the loess-particle removing SiO 2 in LPM can also increase the amount of adsorption of microorganisms, soil enzymes, and fertilizer components such as nitrogen, phosphorous, potassium, calcium, and magnesium [26]. Overall, it is suggested that LPM may be used as a potential complex silicon agent in agriculture.…”