Elucidation of optimum conditions for immobilization of viable cells by using calcium alginate (original) (raw)
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Effect of immobilized cells in calcium alginate beads in alcoholic fermentation
AMB Express, 2013
Saccharomyces cerevisiae cells were immobilized in calcium alginate and chitosan-covered calcium alginate beads and studied in the fermentation of glucose and sucrose for ethanol production. The batch fermentations were carried out in an orbital shaker and assessed by monitoring the concentration of substrate and product with HPLC. Cell immobilization in calcium alginate beads and chitosan-covered calcium alginate beads allowed reuse of the beads in eight sequential fermentation cycles of 10 h each. The final concentration of ethanol using free cells was 40 g L-1 and the yields using glucose and sucrose as carbon sources were 78% and 74.3%, respectively. For immobilized cells in calcium alginate beads, the final ethanol concentration from glucose was 32.9 ± 1.7 g L-1 with a 64.5 ± 3.4% yield, while the final ethanol concentration from sucrose was 33.5 ± 4.6 g L-1 with a 64.5 ± 8.6% yield. For immobilized cells in chitosan-covered calcium alginate beads, the ethanol concentration fro...
Iranian Journal of Biotechnology
Background: Although advantages of immobilization of cells through entrapment in calcium alginate gel beads have already been demonstrated, nevertheless, instability of the beads and the mass transfer limitations remain as the major challenges. Objective: The objective of the present study was to increase the stability, porosity (reduce mass transfer limitation), and cell immobilization capacity of calcium alginate gel beads. Materials and Methods: Sodium alginate was mixed with various concentrations of the starch or sugar and gelled in 2% calcium chloride solution. During the gelling and curing, the starch or sugar leached out of the beads and created micropores. Results: Micro-porous beads prepared with starch were more stable and had higher immobilization capacity than those prepared with sugar. After 24 hours of incubation (curing) of the micro-porous beads prepared with starch in calcium alginate, the solubilization time in citrate buffer was 93 minutes compared to 41 minutes for the control beads (without starch). The compressive strength of the micro-porous beads was also higher (5.62 Mpa) than that of the control beads (5.54 Mpa). The optimal starch concentration for cell immobilization was 0.4%. With this starch concentration, the immobilized Bacillus subtilis and Saccharomyces cerevisiae cell densities were 5.6 × 10 9 and 1.2 × 10 8 cells/beads, respectively. These values were 36.5% and 74% higher than the value obtained for the control beads. This method of immobilization resulted in more uniform cell distribution. Conclusion: Addition of starch to the sodium alginate solution before gelation in calcium chloride solution increased the stability of the beads, increased the immobilized cell density, and resulted in a more uniform cell distribution in the beads.
Optimization of alcoholic fermentation using immobilized yeast cells in calcium alginate gel
Acta Periodica Technologica, 2015
Ethanol is an important industrial chemical with emerging potential as a biofuel to replace fossil fuels. In order to enhance the efficiency and yield of alcoholic fermentation, combined techniques such as cells immobilization and media optimization have been used. The aim of this study was the optimization of sodium alginate concentration and glucose and yeast extract content in the media for ethanol production with immobilized cells of Saccharomyces cerevisiae. Optimization of these parameters was attempted by using a Box-Behnken design using the response surface methodology. The obtained model predicts that the maximum ethanol content of 7.21% (v/v) is produced when the optimal values of sodium alginate concentration and initial content of glucose and yeast extract in the medium are 22.84 g/L, 196.42 g/L and 3.77 g/L, respectively. To minimize the number of yeast cells "eluted" from the alginate beads and residual glucose content in fermented media, additional two sets of optimization were made. The obtained results can be used for further techno-economic analyses of the process to select the optimum conditions of the fermentation process for industrial application.
Polymers
The development of biorefineries brings the necessity of an efficient consumption of all sugars released from biomasses, including xylose. In addition, the presence of inhibitors in biomass hydrolysates is one of the main challenges in bioprocess feasibility. In this study, the application of Ca-alginate hybrid gels in the immobilization of xylose-consuming recombinant yeast was explored with the aim of improving the tolerance of inhibitors. The recombinant yeast Saccharomyces cerevisiae GSE16-T18SI.1 (T18) was immobilized in Ca-alginate and Ca-alginate–chitosan hybrid beads, and its performance on xylose fermentation was evaluated in terms of tolerance to different acetic acid concentrations (0–12 g/L) and repeated batches of crude sugarcane bagasse hemicellulose hydrolysate. The use of the hybrid gel improved yeast performance in the presence of 12 g/L of acetic acid, achieving 1.13 g/L/h of productivity and reaching 75% of the theoretical ethanol yield, with an improvement of 32%...
Xylitol production by Ca-alginate entrapped cells: comparison of different fermentation systems
Enzyme and Microbial Technology, 2003
Candida guilliermondii cells were entrapped in Ca-alginate beads and used for xylitol production from concentrated sugarcane bagasse hemicellulosic hydrolysate in three different fermentation systems, namely 125-ml Erlenmeyer flasks (EF), 2.4-l stirred tank reactor (STR) and 2.4-l basket-type stirred tank reactor (BSTR). The EF system provided a xylitol production of 21.0 g P l −1 , a product yield based on xylose consumption of 0.54 g P g S −1 , and an overall production rate of 0.44 g P l −1 h −1 after 48 h of fermentation. By the STR system, 23.5 g P l −1 was produced after 60 h of fermentation, corresponding to a yield of 0.58 g P g S −1 and a production rate of 0.39 g P l −1 h −1 . As the average volume of the beads decreased by 10.7% (p < 0.05) during this fermentation, a basket was fitted into the reactor vessel to prevent the beads abrasion and thus maintain their integrity. However, the xylitol yield (0.46 g P g S −1 ), production rate (0.21 g P l −1 h −1 ) and concentration (15.0 g P l −1 ) attained by this system were affected by mass-transfer limitations.
Applied Microbiology and Biotechnology, 1990
Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus were immobilized separately in κ-carrageenan-locust bean gum gel beads. The beads were prepared by a dispersion process in a two-phase system (water in oil) and two ranges of bead diameter selected by sieving (0.5–1.0 mm and 1.0–2.0 mm). Fermentations with the two strains were conducted in bench bioreactors in a supplemented whey permeate medium. Free and entrapped cells (two ranges of bead diameter and two levels of initial bead cell load) were grown in mixed culture, and carbohydrate utilization, acid production and cell growth or cell release rate measured. Fermentation rates were influenced by bead diameter and initial cell load of the beads. Beads with high initial cell density increased fermentation rates compared to low cell density beads or free cells. Smaller diameter beads (0.5–1.0 mm) showed a stable tendency (not statistically significant p a > 0.05) towards higher cell release rates, lactose utilization, galactose accumulation and lactic acid production than did larger diameter beads (1.0–2.0 mm). Immobilization of S. salivarius subsp. thermophilus and L. delbrueckii subsp. bulgaricus in separate beads did not seem to affect protocooperation during batch fermentation, and allowed for high cell release rates into the medium.
Applied Microbiology and Biotechnology, 1990
Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus were immobilized separately in κ-carrageenan-locust bean gum gel beads. The beads were prepared by a dispersion process in a two-phase system (water in oil) and two ranges of bead diameter selected by sieving (0.5–1.0 mm and 1.0–2.0 mm). Fermentations with the two strains were conducted in bench bioreactors in a supplemented whey permeate medium. Free and entrapped cells (two ranges of bead diameter and two levels of initial bead cell load) were grown in mixed culture, and carbohydrate utilization, acid production and cell growth or cell release rate measured. Fermentation rates were influenced by bead diameter and initial cell load of the beads. Beads with high initial cell density increased fermentation rates compared to low cell density beads or free cells. Smaller diameter beads (0.5–1.0 mm) showed a stable tendency (not statistically significant p a > 0.05) towards higher cell release rates, lactose utilization, galactose accumulation and lactic acid production than did larger diameter beads (1.0–2.0 mm). Immobilization of S. salivarius subsp. thermophilus and L. delbrueckii subsp. bulgaricus in separate beads did not seem to affect protocooperation during batch fermentation, and allowed for high cell release rates into the medium.