Qinhong Cai

Screening of biosurfactant producers from petroleum hydrocarbon contaminated sources in cold marine environments

An overview of literature about isolating biosurfactant producers from marine sources indicated no such producers have been reported form North Atlantic Canada. Water and sediment samples were taken from petroleum hydrocarbon contaminated coastal and offshore areas in this region. Either n-hexadecane or diesel was used as the sole carbon source for the screening. A modified colony-based oil drop collapsing test was used to cover sessile biosurfactant producers. Fifty-five biosurfactant producers belong to genera of Alcanivorax, Exiguobacterium, Halomonas, Rhodococcus, Bacillus, Acinetobacter, Pseudomonas, and Streptomyces were isolated. The first three genera were established after 1980s with interesting characteristics and limited relevant publications. Some of the 55 isolated strains were found with properties such as greatly reducing surface tension, stabilizing emulsion and producing flocculant. Isolates P6-4P and P1-5P were selected to demonstrate the performance of biosurfactant production, and were found to reduce the surface tension of water to as low as 28 dynes/cm.

Offshore oil spill response practices and emerging challenges

Offshore oil spills are of tremendous concern due to their potential impact on economic and ecological systems. A number of major oil spills triggered worldwide consciousness of oil spill preparedness and response. Challenges remain in diverse aspects such as oil spill monitoring, analysis, assessment, contingency planning, response, cleanup, and decision support. This article provides a comprehensive review of the current situations and impacts of offshore oil spills, as well as the policies and technologies in offshore oil spill response and countermeasures. Correspondingly, new strategies and a decision support framework are recommended for improving the capacities and effectiveness of oil spill response and countermeasures. In addition, the emerging challenges in cold and harsh environments are reviewed with recommendations due to increasing risk of oil spills in the northern regions from the expansion of the Arctic Passage.

Screening of biosurfactant-producing bacteria from offshore oil and gas platforms in North Atlantic Canada

From offshore oil and gas platforms in North Atlantic Canada, crude oil, formation water, drilling mud, treated produced water and seawater samples were collected for screening potential biosurfactant producers. In total, 59 biosurfactant producers belong to 4 genera, namely, Bacillus, Rhodococcus, Halomonas, and Pseudomonas were identified and characterized. Phytogenetic trees based on 16S ribosomal deoxyribonucleic acid (16S rDNA) were constructed with isolated strains plus their closely related strains and isolated strains with biosurfactant producers in the literature, respectively. The distributions of the isolates were site and medium specific. The richness, diversity, and evenness of biosurfactant producer communities in oil and gas platform samples have been analyzed. Diverse isolates were found with featured properties such as effective reduction of surface tension, producing biosurfactants at high rate and stabilization of water-in-oil or oil-in-water emulsion. The producers and their corresponding biosurfactants had promising potential in applications such as offshore oil spill control, enhancing oil recovery and soil washing treatment of petroleum hydrocarbon-contaminated sites.

Microbial degradation of four crude oil by biosurfactant producing strain Rhodococcus sp.

Rhodococcus erythropolis M-25, one of the representative biosurfactant producers, performed effectively during the biodegradation of four crude oil. The microbial degradation efficiency is positively relevant to the API of the crude oil. The chemical dispersant Corexit 9500A did not enhance the biodegradation of the petroleum hydrocarbons during the experimental period. 70.7% of the N-4 oil was degraded after 30days, while in the Corexit 9500A plus sample the biodegradation removal was 42.8%. The Corexit-derived compounds were metabolized by M-25 at the same time of the petroleum hydrocarbons biodegrading. Neither biodegradation nor chemical dispersion process has almost no effect on the biomarker (m/z=231). The saturated methyl-branched fatty acids increased from 37.3%, to 49.4%, when M-25 was exposed with the N-4 crude oil. Similarly, the saturated methyl-branched fatty acids in the membrane of N3-2P increased from 20.25% to 44.1%, when exposed it with the N-4 crude oil.

Removal of Heavy Metals from Mining Wastewater by Micellar-Enhanced Ultrafiltration (MEUF): Experimental Investigation and Monte Carlo-Based Artificial Neural Network Modeling

The removal of copper, nickel, and cobalt ions from synthetic mining wastewater was investigated in this study using micellar-enhanced ultrafiltration (MEUF). The effect of surfactant-to-metal (S/M) ratio and pH on metal rejection and permeate flux were examined. A Monte Carlo-based artificial neural network (ANN) modeling approach was proposed to predict the MEUF performance and to reveal the importance of process parameters. The results showed that model-predicted values were in agreement with experimental data (Rxa0>xa00.99). S/M ratio and pH had relatively greater contributions (30–50%) to the metal rejection rate and permeate flux, whereas sampling time contributed less (10%), which indicated high MEUF efficiency. An S/M ratio of 8.5 with a pH of 8–10 was found to be the optimal condition for MEUF, under which the rejection rates of all three metals exceeded 99% and were in compliance with Canadian environmental standards. Flux decrease and concentration polarization effect were observed during the experimental procedure. Statistical analysis showed that the type of metal examined in this study did not affect MEUF performance.

Use of Sesquiterpanes, Steranes, and Terpanes for Forensic Fingerprinting of Chemically Dispersed Oil

Biomarkers, as complex hydrocarbons in oil from formally living organisms, have been widely used for offshore oil spill fingerprinting. The application of oil dispersants may affect the suitability of existing biomarkers in oil fingerprinting during physicochemical weathering. The existence and concentrations of some biomarkers in chemically dispersed oil (CDO) may differ from those in crude oil and weathered oil. Such differences could affect the diagnostic ratios among different biomarkers and cause difficulties in oil spill fingerprinting. This study thus examined the stability and suitability of three groups of biomarkers, i.e., sesquiterpanes, steranes, and terpanes, for CDO characterization in seawater after application of a representative chemical dispersant (Corexit 9500A). The results indicated that the suitability of sesquiterpanes as biomarkers for CDO identification was affected due to less number of stable diagnostic ratios and overlapped ranges of diagnostic ratios compared to other reference oils. On the contrary, most of the steranes and terpanes could still be applied as biomarkers for CDO characterization. All the selected diagnostic ratios of terpanes were suitable for identification of oil sources. By considering both the stability and suitability, the recommended ranking of biomarkers for CDO was terpanesu2009>u2009steranesu2009>u2009sesquiterpanes. The findings would help improve offshore oil spill fingerprinting methods particularly after application of chemical dispersants.

A novel bioemulsifier produced by Exiguobacterium sp. strain N4-1P isolated from petroleum hydrocarbon contaminated coastal sediment

In this study, Exiguobacterium N4-1P is reported as a bioemulsifier producer for the first time. The strain was found to be closely related to E. oxidotolerans strain T-2-2T, E. antarcticum B7T, and E. antarcticum B7T with similarities of 99.47, 98.70 and 98.63%, respectively. Its phenotypic properties such as metabolic fingerprints, membrane composition, and cell morphology were determined. Different carbon sources were used for bioemulsifier production and diesel was confirmed to stimulate the yield effectively. The produced bioemulsifier is a complex mainly composed of lipopeptides with C16:0 (32.18%) and C18:0 (40.99%) as the primary fatty acids. The produced bioemulsifier could form emulsions effectively with diverse hydrocarbons. No foams were formed during the production and applications, which would facilitate its commercialization. The bioemulsifier was stable over a wide range of salinity (0–25%), pH (2–12), and temperature (below 50 °C). Exiguobacterium N4-1P and the produced bioemulsifier fills knowledge gaps and has promising application potential in diverse fields, especially in environmental engineering.