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Papers by Luis Caicedo

Waste Management & Research, 2010

Stillage re-use in the fermentation stage in ethanol production is a technique used for the reduc... more Stillage re-use in the fermentation stage in ethanol production is a technique used for the reduction of water and fermentation nutrients consumption. However, the inhibitory effect on yeast growth of the by-products and feed components that remains in stillage increases with re-use and reduces the number of possible recycles. Several methods such as ultrafiltration, electrodialysis and advanced oxidation processes have been used in stillage treatment prior its re-use in the fermentation stage. Nevertheless, few studies evaluating the effect of solvent extraction as a stillage treatment option have been performed. In this work, the inhibitory effect of serial stillage recycling over ethanol and biomass production was determined, using acetic acid as a monitoring compound during the fermentation and solvent extraction process. Raw palm oil methyl ester showed the highest acetic acid extraction from the aqueous phase, presenting a distribution coefficient of 3.10 for a 1:1 aqueous phase mixture:solvent ratio. Re-using stillage without treatment allowed up to three recycles with an ethanol production of 53.7 +/- 2.0 g L(-1), which was reduced 25% in the fifth recycle. Alternatively, treated stillage allowed up to five recycles with an ethanol final concentration of 54.7 +/- 1.3 g L(- 1). These results show that reduction of acetic acid concentration by an extraction process with raw palm oil methyl ester before re-using stillage improves the number of recycles without a major effect on ethanol production. The proposed process generates a palm oil methyl ester that contains organic acids, among other by-products, that could be used for product recovery and as an alternative fuel.

Food and Bioprocess Technology, 2010

Fructooligosaccharide production with the fructosyltransferase from free cells of the native stra... more Fructooligosaccharide production with the fructosyltransferase from free cells of the native strain Aspergillus sp. N74 at laboratory level was evaluated. The biomass of the native strain Aspergillus sp. N74 was produced in a sucrose fermentation medium and was employed in the enzymatic reaction in solutions of sucrose and phosphate buffer, where pH, temperature, and initial sucrose concentration effect were evaluated. Fructooligosaccharides and reaction subproducts were identified and quantified by high-performance liquid chromatography. The enzyme produced by the strain Aspergillus sp. N74 possessed hydrolytic and transfructosylating activities that changed with process conditions. The best transfructosylating condition was obtained at 80 min reaction time at pH 5.5, 60 °C, and initial sucrose concentrations higher than 550 g L−1, with fructooligosaccharide production of about 50% w/w (based on initial sucrose concentration) and conversion selectivity higher than 90%. In addition, the transfructosylating and hydrolytic activities ratio was of 20. The high transfructosylating activity showed by the fructosyltransferase produced from the native strain Aspergillus sp. N74 suggest considering it as an alternative for the scale-up production of fructooligosaccharides by means of the whole microorganism at bench and pilot plant levels.

Food and Bioproducts Processing, 2008

Journal of Chemical Technology and Biotechnology, 2009

BACKGROUND: Fructooligosaccharides are important sweeteners produced by sucrose biotransformation... more BACKGROUND: Fructooligosaccharides are important sweeteners produced by sucrose biotransformation. Although fructooligosccharides production has been reported widely, most studies have been carried out at laboratory level. This study evaluates semibatch and continuous fructooligosaccharides production by Aspergillus sp. N74 at bench scale in a mechanically agitated airlift.RESULTS: Sucrose biotransformation to fructooligosaccharides was carried out with biomass harvested after 24 or 48 h of culture. For 6.21 ± 0.33 or 9.66 ± 0.62 g biomass dry weight L−1, the highest FOS yields were obtained at batch operating 62.1 and 66.4% after 26 or 6 h of reaction, respectively. Reduction in fructooligosaccharides yield was observed for both biomass concentrations at semibatch operating, while a comparable yield was obtained during continuous operating (62.1% for 6.21 ± 0.33 g L−1 and a dilution rate 0.016 s−1, and 62.8% for 9.66 ± 0.62 g L−1 and a dilution rate 0.032 s−1). Nevertheless, 1-kestose formation was favored with biomass harvested after 24 h under any operating mode.CONCLUSION: Biomass concentration, reaction time and operating mode have a notable effect on fructooligosaccharides yield and composition. 1-kestose, the most valuable fructooligosaccharide, was obtained in greatest proportion at a biomass concentration 6.21 ± 0.33 g L−1. Under the different operating modes, Aspergillus sp. N74 mycelia and the reactor described are presented as a feasible alternative for scaling up fructooligosaccharides production. Copyright © 2008 Society of Chemical Industry

Papers Vol. 8 núm. 16 julio-diciembre 2012 by Luis Caicedo

"La celulosa bacteriana es un polímero obtenido por fermentación con microrganismos de los género... more "La celulosa bacteriana es un polímero obtenido por fermentación con microrganismos de los géneros Acetobacter, Rhizobium, Agrobacterium y Sarcina, delas cuales la especie más eficiente es la Acetobacter Xylinum. Este polímero presenta la misma estructura química de la celulosa de origen vegetal, pero difiere en su conformación y propiedades fisicoquímicas, lo que lo hace atractivo para diversas aplicaciones, especialmente en las áreas de alimentos, procesos de separación, catálisis y en medicina, gracias a su biocompatibilidad. Sin embargo, el principal problema es la producción a gran escala limitada por los bajos rendimientos, lo que genera la necesidad de desarrollar alternativas que permitan disminuir o eliminar las causas de esta limitación. En este artículo se hace una revisión acerca de la síntesis, producción, propiedades y principales aplicaciones de la celulosa bacteriana, así como de algunas alternativas estudiadas para disminuir los inconvenientes en el escalamiento del proceso"

Waste Management & Research, 2010

Stillage re-use in the fermentation stage in ethanol production is a technique used for the reduc... more Stillage re-use in the fermentation stage in ethanol production is a technique used for the reduction of water and fermentation nutrients consumption. However, the inhibitory effect on yeast growth of the by-products and feed components that remains in stillage increases with re-use and reduces the number of possible recycles. Several methods such as ultrafiltration, electrodialysis and advanced oxidation processes have been used in stillage treatment prior its re-use in the fermentation stage. Nevertheless, few studies evaluating the effect of solvent extraction as a stillage treatment option have been performed. In this work, the inhibitory effect of serial stillage recycling over ethanol and biomass production was determined, using acetic acid as a monitoring compound during the fermentation and solvent extraction process. Raw palm oil methyl ester showed the highest acetic acid extraction from the aqueous phase, presenting a distribution coefficient of 3.10 for a 1:1 aqueous phase mixture:solvent ratio. Re-using stillage without treatment allowed up to three recycles with an ethanol production of 53.7 +/- 2.0 g L(-1), which was reduced 25% in the fifth recycle. Alternatively, treated stillage allowed up to five recycles with an ethanol final concentration of 54.7 +/- 1.3 g L(- 1). These results show that reduction of acetic acid concentration by an extraction process with raw palm oil methyl ester before re-using stillage improves the number of recycles without a major effect on ethanol production. The proposed process generates a palm oil methyl ester that contains organic acids, among other by-products, that could be used for product recovery and as an alternative fuel.

Food and Bioprocess Technology, 2010

Fructooligosaccharide production with the fructosyltransferase from free cells of the native stra... more Fructooligosaccharide production with the fructosyltransferase from free cells of the native strain Aspergillus sp. N74 at laboratory level was evaluated. The biomass of the native strain Aspergillus sp. N74 was produced in a sucrose fermentation medium and was employed in the enzymatic reaction in solutions of sucrose and phosphate buffer, where pH, temperature, and initial sucrose concentration effect were evaluated. Fructooligosaccharides and reaction subproducts were identified and quantified by high-performance liquid chromatography. The enzyme produced by the strain Aspergillus sp. N74 possessed hydrolytic and transfructosylating activities that changed with process conditions. The best transfructosylating condition was obtained at 80 min reaction time at pH 5.5, 60 °C, and initial sucrose concentrations higher than 550 g L−1, with fructooligosaccharide production of about 50% w/w (based on initial sucrose concentration) and conversion selectivity higher than 90%. In addition, the transfructosylating and hydrolytic activities ratio was of 20. The high transfructosylating activity showed by the fructosyltransferase produced from the native strain Aspergillus sp. N74 suggest considering it as an alternative for the scale-up production of fructooligosaccharides by means of the whole microorganism at bench and pilot plant levels.

Food and Bioproducts Processing, 2008

Journal of Chemical Technology and Biotechnology, 2009

BACKGROUND: Fructooligosaccharides are important sweeteners produced by sucrose biotransformation... more BACKGROUND: Fructooligosaccharides are important sweeteners produced by sucrose biotransformation. Although fructooligosccharides production has been reported widely, most studies have been carried out at laboratory level. This study evaluates semibatch and continuous fructooligosaccharides production by Aspergillus sp. N74 at bench scale in a mechanically agitated airlift.RESULTS: Sucrose biotransformation to fructooligosaccharides was carried out with biomass harvested after 24 or 48 h of culture. For 6.21 ± 0.33 or 9.66 ± 0.62 g biomass dry weight L−1, the highest FOS yields were obtained at batch operating 62.1 and 66.4% after 26 or 6 h of reaction, respectively. Reduction in fructooligosaccharides yield was observed for both biomass concentrations at semibatch operating, while a comparable yield was obtained during continuous operating (62.1% for 6.21 ± 0.33 g L−1 and a dilution rate 0.016 s−1, and 62.8% for 9.66 ± 0.62 g L−1 and a dilution rate 0.032 s−1). Nevertheless, 1-kestose formation was favored with biomass harvested after 24 h under any operating mode.CONCLUSION: Biomass concentration, reaction time and operating mode have a notable effect on fructooligosaccharides yield and composition. 1-kestose, the most valuable fructooligosaccharide, was obtained in greatest proportion at a biomass concentration 6.21 ± 0.33 g L−1. Under the different operating modes, Aspergillus sp. N74 mycelia and the reactor described are presented as a feasible alternative for scaling up fructooligosaccharides production. Copyright © 2008 Society of Chemical Industry

"La celulosa bacteriana es un polímero obtenido por fermentación con microrganismos de los género... more "La celulosa bacteriana es un polímero obtenido por fermentación con microrganismos de los géneros Acetobacter, Rhizobium, Agrobacterium y Sarcina, delas cuales la especie más eficiente es la Acetobacter Xylinum. Este polímero presenta la misma estructura química de la celulosa de origen vegetal, pero difiere en su conformación y propiedades fisicoquímicas, lo que lo hace atractivo para diversas aplicaciones, especialmente en las áreas de alimentos, procesos de separación, catálisis y en medicina, gracias a su biocompatibilidad. Sin embargo, el principal problema es la producción a gran escala limitada por los bajos rendimientos, lo que genera la necesidad de desarrollar alternativas que permitan disminuir o eliminar las causas de esta limitación. En este artículo se hace una revisión acerca de la síntesis, producción, propiedades y principales aplicaciones de la celulosa bacteriana, así como de algunas alternativas estudiadas para disminuir los inconvenientes en el escalamiento del proceso"