Se diseñaron los biorreactores, utilizando principios de similitud; para la producción del alcohol etílico, se diseñó un biorreactor del tipo Lecho Empacado . Inmovilización de levaduras en residuos lignocelulósicos para la producción de etanol en biorreactor de lecho empacado. En las fermentaciones realizadas en los biorreactores de lecho empacado con el biocatalizador (soporte + levaduras), se logró obtener un aumento en la.
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Received for review November 23 th, accepted May 16 th, final version May, 31 th Continuous processes with immobilized cells are a good alternative for improving the efficiency and the performance of alcoholic fermentations. The potential use of raw materials obtained from agro-industrial waste as supports for cell immobilization was recently evaluated. In this work, we evaluated the continuous production of ethanol in packed-bed reactors with yeast cells immobilized on wood shaving, cane bagasse, corn leave, and corn cob lignocellulosic waste.
We used glucose as a carbon source to establish the reference conditions and we made the fermentations with commercial sucrose. We also evaluated the glucose syrup obtained from cassava flour as alternative substrate. The experiments were performed on a laboratory level in column reactors of mL.
The cane bagasse was the material on which the highest amount of cells was immobilized. A value of 0. For the fermentation performed with glucose, the productivity reached was A similar value, In the fermentations performed with glucose syrup, a higher amount of ethanol was obtained in the process that used corn cob as the carrier. The results obtained have allowed us to establish the potential this lignocellulosic waste has as carriers for cell immobilization for the continuous production of ethanol, and the possibility of using glucose syrup as an alternative substrate.
Las experimentaciones fueron realizadas a nivel de laboratorio en reactores de columna de mL.
Yeast immobilization in lignocellulosic wastes for ethanol production in packed bed bioreactor
One of the more relevant biofuels for the substitution of fossil fuels is ethanol , which is mainly produced by alcoholic fermentation in batch processes. However, the performance and costs of production of this technology are still high compared to fossil fuels . Many possibilities of optimization have been suggested for obtaining this biofuel, and one of them has to do with the usage of more efficient production technologies.
The continuous processes are an alternative for improving the efficiency and performance of alcoholic fermentation and for reducing the costs of production.
The continuous processes that use immobilized cells show several advantages with respect to continuous processes with free cells [3,18,20]. The immobilization matrixes more frequently used have been polymeric gels like alginate, where the cells are immobilized for entrapment into the gel.
However, this method of immobilization is not too viable on an industrial scale, due to the high cost of raw material and the relative complexity of preparation of the biocatalysts carrier-cell with respect to the operative lifetime of the process [4,21,14].
We also evaluated the glucose syrup obtained from cassava flour as an alternative substrate. The fermenting medium used for the experiments was the following: The pH was set to 5.
Carriers for immobilization The lignocellulosic waste used were wood shaving, cane bagasse, corn leave, and corn cob, which were obtained from some agro industries in the region. We obtained pieces of material of sizes between 3. Immobilization process The cellular immobilization was carried out in empxcado column reactor of mL, provided with a temperature control jacket. A Cole Parmer peristaltic pump model was used, operating at a flow of 0.
The process of immobilization was carried out for 12 h. Batch fermentation Once the immobilization process in the column bioreactor was finished, we began the batch fermentation by pumping the medium fermentation until the reactor filled up.
The fermentation time of 12 h. We took the sample at the end of the fermentation. Continuous fermentation For continuous fermentation, a feeding flow of 1.
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The established time of residence t was 3 h, and the reactor was operated this way for 6 times of residence 18 h. Before starting the continuous process, we carried out the stages of cell immobilization and batch fermentation previously described.
Stable system operation was achieved after the fourth residence time, when the sugar concentration in the samples was similar.
The samples were taken at the output of the reactor, once the system was in a stable state.
Un biorreactor Novela de alta densidad de cultivo de diversas comunidades microbianas
Analytic methods The total sugar quantification was performed by the DNS Dinitrosalicylic acid colorimetric method.
The absorbance reading was done with a spectrophotometer Spectronic Genesis 2, modelserial no. LR at nm .
The concentration of biomass was determined by optic density at nm using a curve of dry weight. The concentration of alcohol was determined by HPLC. We used a CH column with an internal diameter of 7. The flow of the mobile phase was 0. The detection by UV absorbance was set to nm.
The amount of immobilized biomass was established by the modified dry-weight technique . In order to confirm immobilization and determine the differences between the carriers, we obtained images by scanning electronic microscopy SEM. Figure 1 shows the results obtained in the cell immobilization performed on the 4 carriers evaluated.
It is observed that the cane bagasse was the material in which the highest amount of cells was immobilized, 0. The process of immobilization was carried out with a flow of 0.
For the wood shaving and corn cob, we obtained an amount of immobilized biomass of 0. In the case of the corn cob, the immobilization was obtained under the same conditions; that is, a flow of 0.
Revista Facultad de Ingeniería
For the wood shaving, the amount of immobilized biomass was obtained with a flow of 3. The corn leave carrier was the material in which the lowest amount of cells was immobilized. The value obtained was 0. The fermentations with glucose as the carbon source empcado performed using cane bagasse as the carrier. The reactor was fed with fermentation medium throughout the peristaltic pump.
The biorreacror attached to the reactor empxcado was used to retain the cells that were not immobilized within the process. The kinectics of the emacado cells was determined during 12 h in a batch fermentation with an initial amount of cells of 0.
In this system, the substrate consumption and generation of the product was given only by the immobilized cells thanks to the filtering equipment installed biorreactorr the reactor output.
The final concentration of ethanol obtained was Biorrector obtained a consumption of The parameters obtained in the batch process are shown in Table 1. For the continuous process, we used a time of residence of 3 h and a flow of 1.
The samples were taken during 6 t equivalent to 18 h. Prior to the start of the continuous process, we performed a batch stage of 12 h. We noticed empacao the system stabilizes when it passes the fourth time of residence 4 t.
The consumption of glucose was high when it passed the first time of residence 1 t. However, upon reaching stable operation, the value was 1. The production of ethanol obtained at the output of the reactor was The productivity reached was Table 2 shows the parameters obtained in the continuous fermentation. The results obtained in the continuous fermentations are significant if compared to the results obtained by other researchers .
Additionally, we reached a better productivity than Plessas S. We made continuous fermentation using the biocatalysts obtained with the four materials. As a carbon source, we evaluated sucrose and glucose syrup obtained from cassava flour. Figures 4 and 5 show the results obtained for the continuous fermentation carried out with sucrose. As observed in Fig. The highest concentration of ethanol was reached in empacaxo fermentation that used the cane bagasse as a carrier.
Although the sugars are not completely consumed at the end of the bbiorreactor, the production of ethanol was sustained in a very similar value than the one obtained with glucose, reaching a productivity of Table 3 shows the values of productivity reached with the other materials. The productivities reached in fermentations with cells immobilized on corn leaves, corn cob, and wood biorreactorr are similar to each other. The consumption of sucrose in the fermentations is different to the consumption of glucose Fig.
The maximum theoretical yield of sucrose to ethanol is 0. Differences in yield may result from variations in the microenvironmental conditions generated within the bioreactor, probably caused by the particular characteristics of each carrier .
The results of the fermentations carried out with glucose syrup obtained from cassava flour are shown in Figs. The fermentation which produced the highest amount of ethanol was the one using corn cobs as a carrier. These results are very relevant if compared with the values obtained in the traditional batch fermentations as well as the results obtained by other researches, who used different materials in the immobilization of cells for the production of ethanol [11—20].
At the output of the reactor we obtained concentrations from These results are similar to the values obtained with the sucrose. Table 4 shows the parameters obtained in the continuous fermentation with glucose syrup as a carbon source.
However, these values are higher than the ones obtained in the fermentation with glucose. This is possibly due to the fact that glucose syrup contains other fermentable sugars such as maltose. This indicates the potential that glucose syrup has as an alternative substrate for ethanol production. Figure 8 shows the cells immobilized on each of the four evaluated carriers. Initially, the cells have more affinity for folds and rough surfaces. However, as the contact of the cells with the carrier increases, and the fermentation time passes, we expected the immobilization to occur on the whole surface of the carrier.
We could appreciate some differences between the surfaces of the four carriers. The features of the surfaces may change the process of cells immobilization as well as the yield in the production of ethanol.