Valorization of oily sludge waste using biosurfactant-producing bacteria.

Oily sludge generated by the petroleum industry is not only an environmental hazard, but since it contains crude oil too, it is a valuable resource as well. This study demonstrates a methodology for the valorization of the oily sludge that allows the recovery of oil fractions by the action of microbes producing surface-active metabolites. Two bacterial isolates were used in the study that were producing different biosurfactants, identified via FTIR analysis as well as through genomic mapping of the biosurfactant pathways using RAST, ANTISMASH 7.0, STRING databases. Serratia spp. AKBS12, produced a mono-rhamnolipid, while Acinetobacter spp. AKBS16, produced emulsan. Although recovery efficiency of both biosurfactants was similar, the recovery profile with respect to the class of hydrocarbons differed. The rhamnolipid produced by Serratia spp. AKBS12 extracted mono-chained paraffins and linear alkanes, while emulsan, produced by Acinetobacter spp. AKBS16 could extract heavier paraffins. The extraction procedure is simple and involves mixing the biosurfactant with oily sludge at a temperature of 30 °C with an incubation of 9 days. Sulphuric acid precipitation releases the oil trapped in the oily sludge. The study is the first step in developing user-friendly, innovative technologies that can be linked to the concept of a circular economy.

Comparative assessment of soil microbial community in crude oil contaminated sites.

Petroleum refineries generate oily sludge that contains hazardous polycyclic aromatic hydrocarbons (PAH), and hence, its proper disposal is of foremost concern. Analysis of the physicochemical properties and functions of indigenous microbes of the contaminated sites are essential in deciding the strategy for bioremediation. This study analyses both parameters at two geographically distant sites, with different crude oil sources, and compares the metabolic capability of soil bacteria with reference to different contamination sources and the age of the contaminated site. The results indicate that organic carbon and total nitrogen derived from petroleum hydrocarbon negatively affect microbial diversity. Contamination levels vary widely on site, with levels of PAHs ranging from 5.04 to 1.66 × 103 µg kg-1 and 6.20 to 5.64 × 103 µg kg-1 in Assam and Gujarat sites respectively, covering a higher proportion of low molecular weight (LMW) PAHs (fluorene, phenanthrene, pyrene, and anthracene). Functional diversity values were observed to be positively correlated (p < 0.05) with acenaphthylene, fluorene, anthracene, and phenanthrene. Microbial diversity was the highest in fresh oily sludge which decreased upon storage, indicating that immediate bioremediation, soon after its generation, would be beneficial. Improvement in the bio-accessibility of hydrocarbon compounds by the treatment of biosurfactant produced by a (soil isolate/isolate) was demonstrated., with respect to substrate utilization.

Biosurfactants as microbial bioactive compounds in microbial enhanced oil recovery.

Fossil fuels such as petroleum resources continue to be a significant fraction of the energy portfolio. Oil sludge or slops have become an unavoidable waste in the petroleum industries, and their improper disposal measures have led to environmental pollution. Various conventional and traditional practices for disposal and recovery are practiced, but the efficiency of MEOR has led to more promising and efficient ways to recover oil from oil reservoirs and waste sludges. Among the microbial bioactives, biosurfactants are the key players in the whole process. Although, MEOR using biosurfactants has been largely practiced for recovering oil from oil reservoirs, microbial metabolites are also proving to be effective in recovering oil from the waste oily sludges generated as a part of the petroleum production cycle. MEOR stands out as a economically sound alternative over other conventional methods that require large capital investment, heavy energy consumption and varying recovery efficiency. This review describes the scope of MEOR to be useful in reducing and reusing the waste oily sludge accumulation that when untreated causes environmental pollution, allowing sustainable use of natural resources. However, lack of reproducibility at field scale, large scale production of bioactive compounds are the major reasons leading to its incompatibility. The review aims to address the gaps and possible strategies to help speed up the efficiency by thoroughly focusing on the biosurfactant mediated MEOR process dynamics and use of various non-renewable substrates as measure of waste utilization for the production of metabolites. The molecular makeup of these significant molecules after extracting them from the contaminated niche will help discover microbial diversity. Furthermore, the limitations to this biosurfactant assisted MEOR can be solved by using genomic and high throughput approaches to execute an economical implementation at field scale level.