antonio gomez | Universidad Autonoma de Baja California (original) (raw)

Papers by antonio gomez

Aiche Journal, 2000

Bubble columns and airlift photobioreactors can be useful for culturing phototrophic organisms re... more Bubble columns and airlift photobioreactors can be useful for culturing phototrophic organisms requiring light as a nutrient. Light availability in bubble columns and airlift devices is influenced by aeration rate, gas holdup, and the liquid velocity (mixing and turbulence). The photosynthetically generated oxygen also needs to be removed, as excessive dissolved oxygen suppresses photosynthesis. Oxygen removal capacity is governed by the magnitude of the overall gas–liquid mass-transfer coefficient, kLaL. This work characterizes the relevant hydrodynamic and mass-transfer parameters in three air-agitated reactors: bubble column, split-cylinder airlift device and concentric draft-tube sparged airlift vessel. The reactors are then evaluated for culture of the microalga Phaeodactylum tricornutum. All reactors were about 0.06 m3 in working volume, and the working aspect ratio was about 10. Data were obtained in tap water for a base-line comparison and in Mediterranean seawater, as a potential medium for algal culture. A theoretical relationship was developed and proved between kLaL and the aeration rate. In addition, a method based on mechanistic relationships was proved for predicting the liquid circulation velocity and kLaL in airlift reactors. Existing correlations applied satisfactorily to gas holdup and kLaL data obtained in the bubble column. Aqueous solution of sodium chloride (0.15 M) closely resembled seawater in terms of its hydrodynamics and oxygen transfer behavior. Under the conditions tested, all three reactors attained a biomass concentration of about 4 kg·m−3 after ∼260 h. The mean maximum specific growth rate was 0.022 h−1 in all cases at a power input of 109 W·m−3.

Journal of Chemical Technology and Biotechnology, 1994

A mathematical model for light-limited growth of a continuous microalgal culture is proposed. Ave... more A mathematical model for light-limited growth of a continuous microalgal culture is proposed. Average light intensity inside the photobioreactor was calculated, taking light attenuation by algae into account. The biomass absorption coefficient was determined by means of two new parameters, the pigment-free biomass, YB, and the total pigment absorption, Yp (absorption coefficient normalized to total pigment content). The model reproduced the steady states reached and the dynamic behaviour of the system when the dilution rate was changed.

Journal of The American Oil Chemists Society, 1995

n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were conce... more n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were concentrated and purified by a two-step process—formation of urea inclusion compounds followed by preparative high-performance liquid chromatography. These methods had been developed previously with fatty acids from cod liver oil. By the urea inclusion compounds method, a mixture that contained 94% (w/w) stearidonic (SA), eicosapentaenoic (EPA), plus docosahexaenoic (DHA) acids (4:1 urea/fatty acid ratio and 4°C crystallization final temperature) was obtained from cod liver oil fatty acids. Further purification of SA, EPA, and DHA was achieved with reverse-phase C18 columns. These isolations were scaled up to a semi-preparative column. A PUFA concentrate was isolated fromI. galbana with methanol/water (80:20, w/w) or ethanol/water (70:30, w/w). With methanol/water, a 96% EPA fraction with 100% yield was obtained, as well as a 94% pure DHA fraction with a 94% yield. With ethanol/water as the mobile phase, EPA and DHA fractions obtained were 92% pure with yields of 84 and 88%, respectively.

Journal of Biotechnology, 1999

Engineering analyses combined with experimental observations in horizontal tubular photobioreacto... more Engineering analyses combined with experimental observations in horizontal tubular photobioreactors and vertical bubble columns are used to demonstrate the potential of pneumatically mixed vertical devices for large-scale outdoor culture of photosynthetic microorganisms. Whereas the horizontal tubular systems have been extensively investigated, their scalability is limited. Horizontal tubular photobioreactors and vertical bubble column type units differ substantially in many ways, particularly with respect to the surface -to -volume ratio, the amount of gas in dispersion, the gas-liquid mass transfer characteristics, the nature of the fluid movement and the internal irradiance levels. As illustrated for eicosapentaenoic acid production from the microalga Phaeodactylum tricornutum, a realistic commercial process cannot rely on horizontal tubular photobioreactor technology. In bubble columns, presence of gas bubbles generally enhances internal irradiance when the Sun is low on the horizon. Near solar noon, the bubbles diminish the internal column irradiance relative to the ungassed state. The optimal dimensions of vertical column photobioreactors are about 0.2 m diameter and 4 m column height. Parallel east -west oriented rows of such columns located at 36.8°N latitude need an optimal inter-row spacing of about 3.5 m. In vertical columns the biomass productivity varies substantially during the year: the peak productivity during summer may be several times greater than in the winter. This seasonal variation occurs also in horizontal tubular units, but is much less pronounced. Under identical conditions, the volumetric biomass productivity in a bubble column is 60% of that in a 0.06 m diameter horizontal tubular loop, but there is substantial scope for raising this value.

Aiche Journal, 2000

Bubble columns and airlift photobioreactors can be useful for culturing phototrophic organisms re... more Bubble columns and airlift photobioreactors can be useful for culturing phototrophic organisms requiring light as a nutrient. Light availability in bubble columns and airlift devices is influenced by aeration rate, gas holdup, and the liquid velocity (mixing and turbulence). The photosynthetically generated oxygen also needs to be removed, as excessive dissolved oxygen suppresses photosynthesis. Oxygen removal capacity is governed by the magnitude of the overall gas–liquid mass-transfer coefficient, kLaL. This work characterizes the relevant hydrodynamic and mass-transfer parameters in three air-agitated reactors: bubble column, split-cylinder airlift device and concentric draft-tube sparged airlift vessel. The reactors are then evaluated for culture of the microalga Phaeodactylum tricornutum. All reactors were about 0.06 m3 in working volume, and the working aspect ratio was about 10. Data were obtained in tap water for a base-line comparison and in Mediterranean seawater, as a potential medium for algal culture. A theoretical relationship was developed and proved between kLaL and the aeration rate. In addition, a method based on mechanistic relationships was proved for predicting the liquid circulation velocity and kLaL in airlift reactors. Existing correlations applied satisfactorily to gas holdup and kLaL data obtained in the bubble column. Aqueous solution of sodium chloride (0.15 M) closely resembled seawater in terms of its hydrodynamics and oxygen transfer behavior. Under the conditions tested, all three reactors attained a biomass concentration of about 4 kg·m−3 after ∼260 h. The mean maximum specific growth rate was 0.022 h−1 in all cases at a power input of 109 W·m−3.

Journal of Chemical Technology and Biotechnology, 1994

A mathematical model for light-limited growth of a continuous microalgal culture is proposed. Ave... more A mathematical model for light-limited growth of a continuous microalgal culture is proposed. Average light intensity inside the photobioreactor was calculated, taking light attenuation by algae into account. The biomass absorption coefficient was determined by means of two new parameters, the pigment-free biomass, YB, and the total pigment absorption, Yp (absorption coefficient normalized to total pigment content). The model reproduced the steady states reached and the dynamic behaviour of the system when the dilution rate was changed.

Journal of The American Oil Chemists Society, 1995

n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were conce... more n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were concentrated and purified by a two-step process—formation of urea inclusion compounds followed by preparative high-performance liquid chromatography. These methods had been developed previously with fatty acids from cod liver oil. By the urea inclusion compounds method, a mixture that contained 94% (w/w) stearidonic (SA), eicosapentaenoic (EPA), plus docosahexaenoic (DHA) acids (4:1 urea/fatty acid ratio and 4°C crystallization final temperature) was obtained from cod liver oil fatty acids. Further purification of SA, EPA, and DHA was achieved with reverse-phase C18 columns. These isolations were scaled up to a semi-preparative column. A PUFA concentrate was isolated fromI. galbana with methanol/water (80:20, w/w) or ethanol/water (70:30, w/w). With methanol/water, a 96% EPA fraction with 100% yield was obtained, as well as a 94% pure DHA fraction with a 94% yield. With ethanol/water as the mobile phase, EPA and DHA fractions obtained were 92% pure with yields of 84 and 88%, respectively.

Journal of Biotechnology, 1999

Engineering analyses combined with experimental observations in horizontal tubular photobioreacto... more Engineering analyses combined with experimental observations in horizontal tubular photobioreactors and vertical bubble columns are used to demonstrate the potential of pneumatically mixed vertical devices for large-scale outdoor culture of photosynthetic microorganisms. Whereas the horizontal tubular systems have been extensively investigated, their scalability is limited. Horizontal tubular photobioreactors and vertical bubble column type units differ substantially in many ways, particularly with respect to the surface -to -volume ratio, the amount of gas in dispersion, the gas-liquid mass transfer characteristics, the nature of the fluid movement and the internal irradiance levels. As illustrated for eicosapentaenoic acid production from the microalga Phaeodactylum tricornutum, a realistic commercial process cannot rely on horizontal tubular photobioreactor technology. In bubble columns, presence of gas bubbles generally enhances internal irradiance when the Sun is low on the horizon. Near solar noon, the bubbles diminish the internal column irradiance relative to the ungassed state. The optimal dimensions of vertical column photobioreactors are about 0.2 m diameter and 4 m column height. Parallel east -west oriented rows of such columns located at 36.8°N latitude need an optimal inter-row spacing of about 3.5 m. In vertical columns the biomass productivity varies substantially during the year: the peak productivity during summer may be several times greater than in the winter. This seasonal variation occurs also in horizontal tubular units, but is much less pronounced. Under identical conditions, the volumetric biomass productivity in a bubble column is 60% of that in a 0.06 m diameter horizontal tubular loop, but there is substantial scope for raising this value.