Cerro Negro bitumen degradation by a consortium of marine benthic microorganisms

Study on a Strain of Lysinibacillus sp. with the Potential to Improve the Quality of Oil Sands

A strain of Lysinibacillus sp., named as Y316, can degrade heavy fractions such as resins and asphaltenes in oil sand. We used Y316 to degrade oil sand samples for 35 days. After bacterial degradation, the oil sand degradation efficiency was 5.88%, while the degradation efficiency of the control group was only 0.29% under the same conditions. Compared with the control group, the saturated content of oil sand in the degradation group increased from 9.56 to 14.39%. After degradation, the resin and asphaltene fractions decreased by 5.34 and 4.77%, respectively. The results of the vaporizable fraction analysis also confirmed the degradation of heavy fractions and the formation of light fractions. After 35 days of degradation, the vaporizable fractions of saturates increased by 3.76 times. The results indicate that Y316 has great significance for improving the quality of oil sands and assisting in oil sand exploitation.

Indigenous microorganisms residing in oil sands tailings biodegrade residual bitumen

The purpose of this study was to determine the capacity of indigenous microbes in tailings to degrade bitumen aerobically, and if acetate biostimulation further improved degradation. Fluid fine tailings, from Base Mine Lake (BML), were used as microbial inocula, and bitumen in the tailings served as a potential carbon source during the experiment. The tailings were capped with 0.22 μm-filtered BML surface water with or without BML bitumen and acetate addition and incubated for 100 days at 20 °C. CO₂ production and petroleum hydrocarbon reductions (50-70% for the biostimulation treatment) in the tailings were observed. DNA was extracted directly from the tailings, and increased bacterial density was observed by qPCR targeting the rpoB gene in the biostimulated group. 16 S rRNA sequencing was used to determine microbial composition profiles in each treatment group. The microbial communities indigenous to the tailings shifted after the bitumen was added. Acidovorax, Rhodoferax, Pseudomonas and Pseudoxanthomonas spp. significantly increased compared to the original microbial community and demonstrated tolerance to bitumen-based toxicity. The first three genera showed more potential for biostimulation treatment with acetate and may be important bitumen/hydrocarbon-degraders in an oil sands end pit lake environment.

Hydrocarbon biodegradation in oxygen-limited sequential batch reactors by consortium from weathered, oil-contaminated soil

We studied the use of sequential batch reactors under oxygen limitation to improve and maintain consortium ability to biodegrade hydrocarbons. Air-agitated tubular reactors (2.5 L) were operated for 20 sequential 21-day cycles. Maya crude oil – paraffin mixture (13 000 mg/L) was used as the sole carbon source. The reactors were inoculated with a consortium from the rhizosphere of Cyperus laxus, a native plant that grows naturally in weathered, contaminated soil. Oxygen limitation was induced in the tubular reactor by maintaining low oxygen transfer coefficients (kLa < 20.6 h–1). The extent and biodegradation rates increased significantly up to the fourth cycle, maintaining values of about 66.33% and 460 mg·L–1·d–1, respectively. Thereafter, sequential batch reactor operation exhibited a pattern with a constant general trend of biodegradation. The effect of oxygen limitation on consortium activity led to a low biomass yield and non-soluble metabolite (0.45 g SS/g hydrocarbons consumed). The average number of hydrocarbon-degrading microorganisms increased from 6.5 × 107 (cycles 1–3) to 2.2 × 108 (cycles 4–20). Five bacterial strains were identified: Achromobacter (Alcaligenes) xylosoxidans, Bacillus cereus, Bacillus subtilis, Brevibacterium luteum, and Pseudomonas pseudoalcaligenes. Asphaltene-free total petroleum hydrocarbons, extracted from a weathered, contaminated soil, were also biodegraded (97.1 mg·L–1·d–1) and mineralized (210.48 mg CO2·L–1·d–1) by the enriched consortium without inhibition. Our results indicate that sequential batch reactors under oxygen limitation can be used to produce consortia with high and constant biodegradation ability for industrial applications of bioremediation.Key words: sequential batch reactors, oxygen limitation, consortium, hydrocarbon biodegradation.

Is biodegradation of bitumen a source of recalcitrant naphthenic acid mixtures in oil sands tailing pond waters?

Carboxylic acids are transient metabolites during the mineralization of petroleum hydrocarbons. Crude oils, however, vary in their proportion of the hydrocarbon components. Depending on structure, some carboxylic acid metabolites resist further biodegradation and persist in aquatic systems. During the extraction of oil sands bitumen, recalcitrant carboxylic acid mixtures, collectively referred to as naphthenic acids (NAs), are released into the wastewaters. These waters also contain unrecovered bitumen from the oil sands. The unextracted bitumen is often overlooked as a possible source of the petroleum acids. The present article discusses the literature data on the biotransformation of hydrocarbons in bitumen from oil sands to the corresponding petroleum carboxylic acids. Some insight is given on the mechanism of the biodegradation process. The susceptibility to biodegradation is affected by differences in alicyclic carboxylic acids such as carbon chain length, chain branching, and the oddness or evenness of carbon chain containing the carboxylic group, positions where alkyl groups are substituted on the cyclic ring, geometrical isomerism, and number of cyclic rings.