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Several biotechnological processes can show an undesirable formation of emulsions making difficult phase separation and product recovery. The breakup of oil-in-water emulsions stabilized by yeast was studied using different physical and chemical methods. These emulsions were composed by deionized water, hexadecane and commercial yeast (Saccharomyces cerevisiae). The stability of the emulsions was evaluated varying the yeast concentration from 7.47 to 22.11% (w/w) and the phases obtained after gravity separation were evaluated on chemical composition, droplet size distribution, rheological behavior and optical microscopy. The cream phase showed kinetic stability attributed to mechanisms as electrostatic repulsion between the droplets, a possible Pickering-type stabilization and the viscoelastic properties of the concentrated emulsion. Oil recovery from cream phase was performed using gravity separation, centrifugation, heating and addition of demulsifier agents (alcohols and magnetic nanoparticles). Long centrifugation time and high centrifugal forces (2 h/150,000×g) were necessary to obtain a complete oil recovery. The heat treatment (60°C) was not enough to promote a satisfactory oil separation. Addition of alcohols followed by centrifugation enhanced oil recovery: butanol addition allowed almost complete phase separation of the emulsion while ethanol addition resulted in 84% of oil recovery. Implementation of this method, however, would require additional steps for solvent separation. Addition of charged magnetic nanoparticles was effective by interacting electrostatically with the interface, resulting in emulsion destabilization under a magnetic field. This method reached almost 96% of oil recovery and it was potentially advantageous since no additional steps might be necessary for further purifying the recovered oil.

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The use of alternative sources such as biochar can contribute to sustainable agriculture. The objective of this study was to evaluate the effect of fertilization with biochar in combination with mineral fertilizer, growth rates and yield of sunflower cv. Embrapa 122/V2000. The experiment was carried out in a protected environment of UAEAg/CTRN/UFCG in pots with a capacity of 20 dm 3 under a completely randomized experimental design, with treatments arranged in a factorial scheme (5 × 4) and four replicates corresponding to five doses of mineral fertilization 0, 25%, 50%, 75%, and 100% of fertilization indication with NPK (100, 300, and 150 mg kg ) and four doses of biochar, 0; 5% (400 g/pot); 10% (800 g/pot) and 15% (1100 g/pot) calculated on the basis of the soil volume. Fertilization with biochar promoted an increase in sunflower growth rates in the evaluation periods. The combination of 50: 150: 75 mg kg -1 of NPK and 400 g/pot of biochar promotes higher production of sunflower (23.91 g/plant).

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