Yeasts and bacterial biosurfactants as demulsifiers for petroleum derivative in seawater emulsions

Abstract Oil sludge or waste generated in transport, storage or refining forms highly stable mixtures due to the presence and additives with surfactant properties and water forming complex emulsions. Thus, demulsification is necessary to separate this residual oil from the aqueous phase for oil processing and water treatment/disposal. Most used chemical demulsifiers, although effective, are environmental contaminants and do not meet the desired levels of biodegradation. We investigated the application of microbial biosurfactants as potential natural demulsifiers of petroleum derivatives in water emulsions. Biosurfactants crude extracts, produced by yeasts (Candida guilliermondii, Candida lipolytica and Candida sphaerica) and bacteria (Pseudomonas aeruginosa, Pseudomonas cepacia and Bacillus sp.) grown in industrial residues, were tested for demulsification capacity in their crude and pure forms. The best results obtained were for bacterial biosurfactants, which were able to recover about 65% of the seawater emulsified with motor oil compared to 35–40% only for yeasts products. Biosurfactants were also tested with oil-in-water (O/W) and water-in-oil (W/O) kerosene model emulsions. No relationship between interfacial tension, cell hydrophobicity and demulsification ratios was observed with all the biosurfactants tested. Microscopic illustrations of the emulsions in the presence of the biosurfactants showed the aspects of the emulsion and demulsification process. The results obtained demonstrate the potential of these agents as demulsifiers in marine environments

Synthesis and wound healing performance of new water-soluble chitosan derivatives

In present work, an efficient method for the preparation of water-soluble chitosan (CS) is reported. It is based on simple synthetic method, which is easy to handle and delivered good water solubility. This article describes the effect of various factors such as the concentration of reactants and the amount of solvents on the reactions' outcome as well as cytocompatibility of the resulting water-soluble CS derivatives. CS derivatives with different ratios of polyethyleneimine (PEI) (80:20 (CP1), 90:20 (CP2), 95:5 (CP3), 99:1 (CP4), and 99.6:0.4 [CP5]), at optimized conditions (50 g of CS, 1 L of 0.5 M acetic acid solution at 80°C for 24 h) were synthesized. It was noted that the amount of PEI was critical for the cytocompatibility, decreasing the amount of PEI led to increasing the cytocompatibility of the obtained water soluble CS derivatives. To show the biomedical and drug delivery applications of the newly synthesized CS derivative, this was used to prepare membranes by freeze-drying and was loaded with thyroxine, respectively. The angiogenic potential of the thyroxine loaded membranes was tested in chorio allantoic membrane assay, which showed good level of neovascularization. For wound healing studies full thickness wounds rat model was used and thyroxine loaded hydrogels showed complete wound healing at day 23