Table 1.
Characterization of Mexican crude oils utilized in this study.
Fig 1.
Optical microscopy of a spore suspension of the fungus Aspergillus sp. IMPMS7.
Magnification 20x.
Fig 2.
Neighbor-joining phylogenetic tree of Aspergillus species based on D1/D2 26S rRNA gene.
Fig 3.
DSC thermograms for O/W emulsion with medium crude oil.
Only the frozen cycle that give information about continuous phase are showed.
Fig 4.
Particle size distribution for O/W emulsion with medium crude oil.
Fig 5.
Photographs showing separation of water in the O/W emulsions prepared I) (a) without fungal spore, with fungal spores at a concentration of (b) 2 and (c) 3.5 g/L. Conditions: T = 45°C, 24 h of incubation. II) Micrograph of emulsion. and III) Micrograph after breaking of emulsion by spores. 20x.
Fig 6.
Effect of time on separation of water of O/W emulsions at 25°C with: medium(●, —), (▲, –––) heavy and extra heavy crude (▼, –⋅–) at 2.0 g/L spore concentration.
The continue, discontinue and discontinue-point line represent hyperbolic curves obtained from least squares fitting. The vertical grey discontinue lines represents the k value and the horizontal grey discontinue line represent the %WSmax with have the 50% of its maximum valued. The results are the average of three experiments. The water segregation values corresponds to the difference between each experiment with spores and water segregated for the emulsion without the addition of spores at the same time (blank). Water segregated was determined by Karl-Fisher method.
Table 2.
Half-life of emulsions prepared with Mexican crude oils incubated with 2 g/L of spores of Aspergillus sp IMPMS7, including standard errors as calculated from the least square fitting procedure.
Fig 7.
Microphotographs showing separation of water in the O/W emulsions, A) O/W emulsion from extra-heavy crude oil without spores, (B) O/W emulsion from heavy crude oil immediately after the addition of fungal spores (3.5 g/L). The spores are visible within both the crude oil and water phases (arrows), (c) After breaking of emulsion by spores. Magnification at 40 x.
Fig 8.
Behavior of the fluorescence intensity of the hydrocarbon emulsion in a water-surfactant dispersion.
A) Spectrum 3D of the HCO emulsion in NPE solution at 2 ppm. B) Emission spectra (λex = 300 nm) of the emulsion dispersion at 2 ppm HCO (continuous line) and 20 ppm (dotted line). C) 3D Spectrum HCO NPE emulsion solution at a concentration of 20 ppm. D) Behavior of the emulsion dispersion in NPE solution depends on HCO aggregation.
Fig 9.
Fluorescence emission as a function of time for an O/W emulsion suspended in water and in presence of fungal spores.
Conditions: λex = 290 nm, λem = 340 nm; O/W emulsion concentration = 20 ppm; 1.0 g/L of fungal spores were added at t = 4 min (dashed line), temperature T = 34°C. Results shown are representative of 3 different experiments.
Fig 10.
Dispersed aqueous solutions showing A) the emission spectra of crude oil (—), crude oil with fungal spores (–––), O/W emulsion (● ● ●) and O/W emulsion with fungal spores (–● – ● –); and B) the I365/I340 ratio of crude oil (1), crude oil with fungal spores (2), O/W emulsion (3), O/W emulsion with fungal spore (4), the I339/I326 ratio of O/W emulsion (5), O/W emulsion broken in presence of demulsifying agent (6) and O/W emulsion treated with MW irradiation at 60°C (7), (5, 6 y 7) data in ref. [3]. Conditions of fluorometric studies: λex = 290 nm, T = 25°C.