• KSBB Journal
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• v.26 no.4
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• pp.328-332
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• 2011

Ethanol production using glycerol as a carbon source was performed by Enterobacter aerogenes immobilized on calcium alginate beads. To improve the ethanol production, the optimal conditions such as loading amount of immobilized cells and glycerol concentration were investigated. The optimal loading amount of immobilized cells and glycerol concentration were 10 mL of calcium alginate bead and 10 g/L, respectively. Consequently, glycerol consumption rate, ethanol concentration and yield were 0.32 g/$L{\cdot}h$, 3.38 g/L and 0.43 g/g on the batch production, respectively. Continuous production of ethanol was successfully achieved using two types of immobilized cell reactors (continuous stirred tank reactor and packed bed reactor) from 10 g/L of glycerol. In the continuous stirred tank reactor, glycerol consumption, ethanol concentration, specific productivity and yield were 9.8 g, 4.67 g/L, 1.17 g/$L{\cdot}h$, 0.48 g/g, respectively. The concentration of produced ethanol was 38-44% higher comparison to batch fermentation, and continuous stirred tank reactor showed better performance than packed bed reactor.

• Environmental Engineering Research
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• v.15 no.3
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• pp.149-156
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• 2010

The objective of this study was to investigate microbial removal using layered double hydroxides (LDHs) and iron (hydr)oxides (IHs) immobilized onto granular media. Column experiments were performed using calcium alginate beads (CA beads), LDHs entrapped in CA beads (LDH beads), quartz sand (QS), iron hydroxide-coated sand (IHCS) and hematite-coated sand (HCS). Microbial breakthrough curves were obtained by monitoring the effluent, with the percentage of microbial removal and collector efficiency then quantified from these curves. The results showed that the LDH beads were ineffective for the removal of the negatively-charged microbes (27.7% at 1 mM solution), even though the positively-charged LDHs were contained on the beads. The above could be related to the immobilization method, where LDH powders were immobilized inside CA beads with nano-sized pores (about 10 nm); therefore, micro-sized microbes (E. coli = 1.21 ${\mu}m$) could not diffuse through the pores to come into contact with the LDHs in the beads, but adhere only to the exterior surface of the beads via polymeric interaction. IHCS was the most effective in the microbial removal (86.0% at 1 mM solution), which could be attributed to the iron hydroxide coated onto the exterior surface of QS had a positive surface charge and, therefore, effectively attracted the negatively-charged microbes via electrostatic interactions. Meanwhile, HCS was far less effective (35.6% at 1 mM solution) than IHCS because the hematite coated onto the external surface of QS is a crystallized iron oxide with a negative surface charge. This study has helped to improve our knowledge on the potential application of functional granular media for microbial removal.

• KSBB Journal
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• v.23 no.1
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• pp.59-64
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• 2008

Optimum conditions for production of casein phosphopeptides (CPP) from sodium casenate by immobilized cell culture of Streptococcus faecalis var. liquefaciens were investigated. Immobilized cells were made by mixing 60% sodium alginate solution with an equal volume of culture broth at the end of exponential phase and subsequently dropping the mixture into $CaCl_{2}$ solution. Optimum conditions for CPP production by the immobilized cells were the same as those ($50^{\circ}C$, pH 7.0, and 10% substrate concentration) by the crude enzyme solution from the supernatant of culture broth. Optimum loading volume of the immobilized cells into a batch reactor was 30% (w/v). Using a continuous reactor loaded by the immobilized cells under the identified optimal conditions, we were able to produce CPP continuously up to 30 days with a maximum CPP conversion efficiency of 20%.

• Analytical Science and Technology
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• v.23 no.2
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• pp.172-178
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• 2010

Glutathione S-transferase is known to play a crucial role in detoxification in many cases. To develop a herbicide detection biosensor, we in this study attempted to immobilize glutathione S-transferase enzyme on solid supports, polystyrene and agarose, and Na-alginate. These matrixes were attractive materials for the construction of biosensors and might also have utility for the production of immobilized enzyme bioreactors. We also compared the activities of glutathione-S-transferase immobilized OsGSTF3 and free OsGSTF3. The specific activity of the free enzyme in solution was 3.3 higher than the immobilized enzyme. These results suggest that 50% of the enzyme was bound with the catalytic site in polystyrene-alkylamine bead and immobilized enzymes showed 80% remaining activity until 3 times reuse.

• KSBB Journal
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• v.8 no.4
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• pp.313-319
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• 1993

Methyl fructoside was synthesized from sucrose and methanol using an immobilized invertase. The enzyme was covalently bound by glutaraldehyde on porous silica coated with polyethyleneimine to give loading capacity of 120mg of invertase per one gram of dry porous silica and effective activity of 100U per one milligram of bound invertase. Polyethyleneimine coating imparted a hydrophillic character, good activity retention and high loading capacity to the surface of porous silica as well as hydrophillic microenviroment in the vicinity of bound invertase. The immobilized enzyme was formed into an alginate-enclosed silica bead to have enough activity for methyl fructoside synthesis from aqueous methanol-sucrose solution. Using the alginate-enclosed biocatalyst the yield of methyl fructoside was obtained as high as 55.9% from aqueous 30% (v/v) methanol and 0.291mo1/l sucrose with 2U/ml activity at $25^{\circ}C$, pH 4.8.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.154-157
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• 2004

Immobilized cells of Aspergillus niger was employed to produce citric acid by fermentation of milk factory waste water. A. niger ATCC 9142 as a citric acid production strain was cultured for 3 days and was entrapped with Ca-alginate bead about 2.5∼3.5 mm. The optimal pH and temperature were estimated to be 3.0 and $30^{\circ}C$, respectively. Dilution rate for fermentation was calculated to be $0.025 h^{－1}$ . Maximum amount of citric acid was obtained at 4.5 g/$\ell$ with the optimized fermentation condition. The yield of citric acid produced by immobilized A. niger ATCC 9143 was 70.3%. The yield was increased by 20% with immobilized cell, compared to that of the shake flask culture. Hence, the milk factory waste water is worthy to be used for the substrate of citric acid fermentation.

• Journal of Microbiology and Biotechnology
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• v.25 no.12
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• pp.2058-2071
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• 2015

A comparative study was conducted to evaluate precision and accuracy in controlling the temperature dependence of encapsulated microbial time-temperature integrators (TTIs) developed using two different emulsification techniques. Weissela cibaria CIFP 009 cells, immobilized within 2% Na-alginate gel microbeads using homogenization (5,000, 7,000, and 10,000 rpm) and Shirasu porous glass (SPG) membrane technologies (10 μm), were applied to microbial TTIs. The prepared micobeads were characterized with respect to their size, size distribution, shape and morphology, entrapment efficiency, and bead production yield. Additionally, fermentation process parameters including growth rate were investigated. The TTI responses (changes in pH and titratable acidity (TA)) were evaluated as a function of temperature (20℃, 25℃, and 30℃). In comparison with conventional methods, SPG membrane technology was able not only to produce highly uniform, small-sized beads with the narrowest size distribution, but also the bead production yield was found to be nearly 3.0 to 4.5 times higher. However, among the TTIs produced using the homogenization technique, poor linearity (R²) in terms of TA was observed for the 5,000 and 7,000 rpm treatments. Consequently, microbeads produced by the SPG membrane and by homogenization at 10,000 rpm were selected for adjusting the temperature dependence. The E_a values of TTIs containing 0.5, 1.0, and 1.5 g microbeads, prepared by SPG membrane and conventional methods, were estimated to be 86.0, 83.5, and 76.6 kJ/mol, and 85.5, 73.5, and 62.2 kJ/mol, respectively. Therefore, microbial TTIs developed using SPG membrane technology are much more efficient in controlling temperature dependence.

• Food Science and Biotechnology
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• v.14 no.5
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• pp.566-571
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• 2005

Process of screw-pumping system (SPS) was optimized for mass production of encapsulated bifidus. SPS entrapment device was composed of feeding component, with optimized nozzle size and length of 18G (0.91 cm) and 4 mm, respectively, screw pump, and 37-multi-nozzle. Screw component had five wing turns [radius (r)=26 to 15 mm] from top to bottom of axis at 78-degree angle from middle of the screw, and two wings were positioned at screw edge to push materials toward nozzle. For nozzle component, 37 nozzles were attached to 20-mm round plate. Air compressor was attached to SPS to increase productivity of encapsulated bifidus. This system could be operated with highly viscous (more than 300 cp) materials, and productivity was higher than $1128\;{\pm}\;30\;beads/min$. Viability of encapsulated bifidus was $5.45\;{\times}\;10^8\;cfu$/bead, which is superior to that of encapsulated bifidus produced by other methods ($2.51{\times}10^8\;cfu$/bead). Average diameter of produced beads was $2.048\;{\pm}\;0.003\;mm$. Survival rate of SPS-produced encapsulated bifidus was 90% for Simulator of the Human Intestinal Microbial Ecosystem test and 88% in fermented milk (for 14 days). These results show SPS is effective for use in development of economical system for mass production of viable encapsulated bifidus.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.648-653
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• 2006

As an alternative for the traditional materials packed in biofilters treating gaseous VOCs, a novel packing material has been developed and tested. In the packing material(named as Hydrogel Bead, HB), pollutant-degrading microorganisms were immobilized in hydrogel consisted of alginate, polyvinyl alcohol(PVA), and powdered activated carbon. A closed-bottle study showed that the HB rapidly removed gaseous styrene without the losses of adsorption and biodegradation capacity. Biofilter column experiments using the HBs also demonstrated that greater than 95% of removal efficiencies were found at an inlet styrene loading rate of $245g/m^3/hr$, which was higher biofilter performance than other elimination capacity reported earlier. Furthermore, when the inlet styrene concentration increased stepwise, the adsorption played an important role in overall styrene removals. The absorbed styrene was found to be biodegraded in the following low inlet loading condition. Consequently, the new HB material is able to successfully minimize the drawbacks of activated carbon(necessity of regeneration) and biological processes(low removal capacity at dynamic loading conditions), and maximize the overall performance of biofilter systems treating VOCs.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.2
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• pp.99-105
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• 2000

Cell-Cell interaction and the extracellular matrix (ECM) are belisved to play essential roles during in vitro culturing of primary hepatocytes in the control of differentiation and in the maintenance of tissue spcific functions. The objective of this study was to examine the effects of degree of cell-cell contact (DCC) on liver sperific function of rat promary hepatocytes. Hepatocyte aggregates with various with various degrees of cell-cell contantact, I. e., dispersed cell, longish aggregate, rugged aggregate, and smooth spheroid were obtained at 1, 5-6, 15-20, and 36-48 hrs, respectively in suspension cultures grown in spinner flasks embedded in Caalginate bead and collagen gel in order. The may result from mass transfer limitation and shear damage caused by agitation during aggregation. The rugged aggregate showed a higer viability and albumin secretion rate than the dispersed cells or the other aggregates. This result indicates the possible enhancement of a bioartificial liver's (BAL) performance using primary hepatocytes and the reduction in time to prepare a BAL through optimization of the immobilization time.