Assessing the Effect of Boswellia Serrata Extract on Fouling of Alloy 6061 Aluminum in Artificial Seawater Slurry

The fouling behavior of Alloy 6061 aluminum in artificial seawater in the presence of Boswellia serrata extract was investigated. Fouling is one of the major issues that occurred commonly in the marine environment. Experiments were conducted to develop a model for fouling propensity. A response surface method was used to develop a model to predict fouling behavior. The model predicts the effect of the variables on fouling in artificial seawater medium in the presence of B. serrata extract. The experimental variables chosen were temperature, flow rate and time. Performance of the regression model calculated by the response surface methodology was verified with the analysis of variance technique. The model equation that was proposed using the response surface methodology showed good agreement with the experimentally obtained data.

Adaptation of Dinoroseobacter shibae to oxidative stress and the specific role of RirA

Dinoroseobacter shibae living in the photic zone of marine ecosystems is frequently exposed to oxygen that forms highly reactive species. Here, we analysed the adaptation of D. shibae to different kinds of oxidative stress using a GeLC-MS/MS approach. D. shibae was grown in artificial seawater medium in the dark with succinate as sole carbon source and exposed to hydrogen peroxide, paraquat or diamide. We quantified 2580 D. shibae proteins. 75 proteins changed significantly in response to peroxide stress, while 220 and 207 proteins were differently regulated by superoxide stress and thiol stress. As expected, proteins like thioredoxin and peroxiredoxin were among these proteins. In addition, proteins involved in bacteriochlophyll biosynthesis were repressed under disulfide and superoxide stress but not under peroxide stress. In contrast, proteins associated with iron transport accumulated in response to peroxide and superoxide stress. Interestingly, the iron-responsive regulator RirA in D. shibae was downregulated by all stressors. A rirA deletion mutant showed an improved adaptation to peroxide stress suggesting that RirA dependent proteins are associated with oxidative stress resistance. Altogether, 139 proteins were upregulated in the mutant strain. Among them are proteins associated with protection and repair of DNA and proteins (e. g. ClpB, Hsp20, RecA, and a thioredoxin like protein). Strikingly, most of the proteins involved in iron metabolism such as iron binding proteins and transporters were not part of the upregulated proteins. In fact, rirA deficient cells were lacking a peroxide dependent induction of these proteins that may also contribute to a higher cell viability under these conditions.

Biodegradation of crude oil by Ralstonia pickettii under high salinity medium

Bacterium Ralstonia pickettii has ability to survive and thrive in low nutrient condition as well as a capability to remediate some pollutants and using them as carbon and energy source. In this study, the ability of R. pickettii on biodegradation of crude oil under high salinity medium was investigated. R. pickettii was pre-incubated in nutrient broth (NB) medium and then, washed and transferred to artificial seawater medium. Crude oil was added to each culture and incubated for 7 and 14 days. The biodegradation of crude oil was analysed using Gas chromatography mass spectrometry (GC-MS). The result showed that R. pickettii had successfully degraded the crude oil in the high salinity artificial seawater. The incubation on 7 and 14 days did not show a significant effect on the number of the degraded compounds. The optimum recovery percent was obtained from the derivation of 2,6,10,14-tetramethyl hexadecane with the recovery percentage of 12.7% and 16.0% for 7 and 14 days respectively. This study indicates that R. picketti can be potentially used for bioremediation of crude oil under high salinity environments.