The role of indigenous bacterial and fungal soil populations in the biodegradation of crude oil in a desert soil

Abstract

The biodegradation capacity of indigenous microbial populations was examined in a desert soil contaminated with crude oil. To evaluate biodegradation, soil samples supplemented with 5, 10 or 20% (w/w) of crude oil were incubated for 90 days at 30 degrees C. The effect of augmentation of the soil with vermiculite (50% v/v) as a bulking agent providing increased surface/volume ratio and improved soil aeration was also tested. Maximal biodegradation (91%) was obtained in soil containing the highest concentration of crude oil (20%) and supplemented with vermiculite; only 74% of the oil was degraded in samples containing the same level of crude oil but lacking vermiculite. Gas chromatograms of distilled fractions of crude oil extracted from the soil before and after incubation demonstrated that most of the light and part of the intermediate weight fractions initially present in the oil extracts could not be detected after incubation. Monitoring of microbial population densities revealed an initial decline in bacterial viable counts after exposure to oil, presumably as a result of the crude oil's toxicity. This decline was followed by a steep recovery in microbial population density, then by a moderate increase that persisted until the end of incubation. By contrast, the inhibitory effect of crude oil on the fungal population was minimal. Furthermore, the overall increased growth response of the fungal population, at all three levels of contamination, was about one order of magnitude higher than that of the bacterial population.

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“…The effects on fungal diversity were 327 more marked than that observed on prokaryotic diversity, corroborating Embar (2006), 328 who reported a rapid increase in abundance and shift in diversity in the fungal 329 community in response to oil contamination. The strong effect of oil on the fungal 330 diversity may also be explained by metabolic differences between eukaryotes and 331 Planctomycetes.…”

Ex-Situ Studies on Biodegradation of Artificially Enriched Kerosene and Diesel Soils by Fungal Isolates

“…Samples were excavated every fifteen days and analyzed for residual kerosene, diesel and fungal population. The whole experiments were carried out in triplicates (Embar et al 2006). …”

Biorremediação de solos contaminados por petróleo e seus derivados

“…Todavia, mesmo quando o meio é totalmente acondicionado ao cultivo dos microorganismos, a biodegradação pode ser afetada, principalmente, devido à capacidade intrínseca de cada microorganismo de metabolizar uma substância qualquer. Por exemplo, de acordo com Embar et al (2006), alguns microorganismos sobrevivem em condições ambientais extremamente adversas. Adicionalmente, pesquisas comprovam que diferentes microorganismos podem degradar diferentes substâncias, dentre estas, substâncias recalcitrantes, como os hidrocarbonetos de petróleo.…”

“…Artigo Article quisas sugerem que devido à elevada diversidade de compostos em solos contaminados por petróleo e derivados, estudos preliminares à biorremediação são de suma importância para o tratamento dessas matrizes ambientais (Embar et al, 2006). Salienta-se que, a princípio, o fator crítico para defi nir se a biorremediação é a técnica mais apropriada para o tratamento do local contaminado é a biodegradabilidade do contaminante.…”