• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1234-1241
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• 2016

Methanol is a versatile compound that can be biologically synthesized from methane (CH₄) by methanotrophs using a low energy-consuming and environment-friendly process. Methylocella tundrae is a type II methanotroph that can utilize CH₄ as a carbon and energy source. Methanol is produced in the first step of the metabolic pathway of methanotrophs and is further oxidized into formaldehyde. Several parameters must be optimized to achieve high methanol production. In this study, we optimized the production conditions and process parameters for methanol production. The optimum incubation time, substrate, pH, agitation rate, temperature, phosphate buffer and sodium formate concentration, and cell concentration were determined to be 24 h, 50% CH₄, pH 7, 150 rpm, 30℃, 100 mM and 50 mM, and 18 mg/ml, respectively. The optimization of these parameters significantly improved methanol production from 0.66 to 5.18 mM. The use of alginate-encapsulated cells resulted in enhanced methanol production stability and reusability of cells after five cycles of reuse under batch culture conditions.

• Applied Biological Chemistry
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• v.27 no.2
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• pp.112-118
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• 1984

Inverase was entrapped in calcium alginate gel. The immobilized beads had excellent uniform size and configuration. To screen the optimal conditions possessing high enzyme activity, effects of sodium alginate concentration, $CaCl_2$ concentration, and the incubation time of beads in $CaCl_2$ solution during the immobilization procedure were investigated. Immobilized beads prepared from the optimal conditions had 18.8 units per ml of gel, which is equivalent to 68% of the activity of soluble enzyme. Several kinetic parameters were determined: Km value. 143 mM; optimum pH, 4.5; optimum temperature, $50^{\circ}C$. Enzyme loading capacity was 150 mg per 20 ml gel. No significant decrease in sugar conversion was observed during the column operation for 6 days.

• Journal of the East Asian Society of Dietary Life
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• v.21 no.5
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• pp.731-738
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• 2011

Cholesterol is the precursor of various steroid hormones, bile acid, and vitamin D with functions related to regulation of membrane permeability and fluidity. However, the presence of excess blood cholesterol may lead to arteriosclerosis and hypertension. Moreover, dietary cholesterol may affect blood cholesterol levels. Generally, cholesterol determination is performed by spectrophotometric or chromatographic methods, but these methods are very time consuming and costly, and require complicated pretreatment. Thus, the development of a rapid and simple analysis method for measuring cholesterol concentration in food is needed. Multi-walled carbon nanotube (MWCNT) was functionalized to MWCNT-$NH_2$ via MWCNT-COOH to have high sensitivity to $H_2O_2$. The fabricated MWCNT-$NH_2$ was attached to a glassy carbon electrode (GCE), after which Prussian blue (PB) was coated onto MWCNT-$NH_2$/GCE. MWCNT-$NH_2$/PB/GCE was used as a working electrode. An Ag/AgCl electrode and Pt wire were used as a reference electrode and counter electrode, respectively. The sensitivity of the modified working electrode was determined based on the amount of current according to the concentration of $H_2O_2$. The response increased with an increase of $H_2O_2$ concentration in the range of 0.5~500 ${\mu}M$ ($r^2$=0.96) with a detection limit of 0.1 ${\mu}M$. Cholesterol oxidase was immobilized to aminopropyl glass beads, CNBr-activated sepharose, Na-alginate, and toyopearl beads. The immobilized enzyme reactors with aminopropyl glass beads and CNBr-activated sepharose showed linearity in the range of 1~100 ${\mu}M$ cholesterol. Na-alginate and toyopearl beads showed linearity in the range of 5~50 and 1~50 ${\mu}M$ cholesterol, respectively. The detection limit of all immobilized enzyme reactors was 1 ${\mu}M$. These enzyme reactors showed high sensitivity; especially, the enzyme reactors with CNBr-activated sepharose and Na-alginate indicated high coupling efficiency and sensitivity. Therefore, both of the enzyme reactors are more suitable for a cholesterol biosensor system.

• Applied Biological Chemistry
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• v.44 no.3
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• pp.185-190
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• 2001

Alginate, a well-known biopolymer, is universally applied for immobilization of microbial cells. Biosorption characteristics of lead by waste biomass of immobilized A. niger beads, used in fermentation industries to produce citric acid, were studied. The immobilized A. niger beads, prepared via capillary extrusion method using calcium chloride, were applied in the removal of lead. Pb uptake was the highest in A. niger beads cells grown for 3 days with medium producing citric acid (12% sucrose, 0.5% $NH_4NO_3$, 0.1% $KH_2PO_4$, and 0.025% $MgSO_4$). Lead uptake by the immobilized A. niger beads and free A. niger mycellia beads increased sharply with time. However, while uptake by the immobilized A. niger beads continued to increase slowly, that by free A. niger mycellia beads stopped after 30 min. The optimum pH and temperature of lead uptake were found to be 6 and $35^{\circ}C$, respectively. The maximum uptake of lead was achieved with $50{\sim}100$ beads and 50 ml lead solution in a 250-ml Erlenmeyer flask, while, at over 100 beads, uptake of the lead decreased. The order of biosorption capacity for heavy metals was Pb>Cu>Cd. Pb uptake capacity of the immobilized A. niger beads treated with 0.1 M $CaCI_2$, 0.1 M NaOH, and 0.1 M KOH decreased compared to the untreated beads. On testing the desorption of Pb from the immobilized A. niger beads, re-uptake of Pb was found possible after desorption of the binding metal with 0.1 M HCI.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.2
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• pp.147-150
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• 2003

Water toxicity monitoring based on the continuous cultivation of Photobacterium phorphoreum is presented. Normally, after 10 days of operation, a dark variant, which emits no light, appears and dominates the population, resulting in a rapid decrease in bioluminescence. Therefore, to overcome this problem, a fluidized-bed reactor is used in which alginate-immobilized cells are grown and leaking cells are continuously released into the effluent Experimental results revealed that the dominance of dark variants was suppressed inside the immobilized beads, thereby mitigating the rapid loss of bioluminescence. Plus, a high dilution rate (1.2 h$\^$-1/) prevented the occurrence of other microbial contamination in the reactor The concentration and bioluminescence of the released cells were sufficient to measure the water toxicity for more than 4 weeks.

• Microbiology and Biotechnology Letters
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• v.25 no.1
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• pp.68-74
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• 1997

The conversion of D-sorbitol to L-sorbose by Gluconobater suboxydans was analyzed, and continuous production of L-sorbose was carried out in immobilized cell reactors. L-Sorbose production by high densities of resting cells was more effective than by conventional batch fermentations. Sorbitol dehydrogenase, an enzyme converting D-sorbitol to L-sorbose, did not suffer from substrate inhibition, but from product inhibition. When L-sorbose production was carried out with Ca-alginate-immobilized cells, about 60 g/l of L-sorbose was obtained. On the other hand, when the corn steep liquor (CSL) concentration of medium was reduced to 0.08%, 80 g/l of L-sorbose was obtained. Outgrowth inside the immobilized carriers was thought to block the pores of the carriers so that substrate could not easily diffuse through the carriers. Continuous production of L-sorbose was well accomplished in a bubble column reactor, and 6. 5 g/l.h of productivity and 81.2% of yield were obtained at a substrate feeding rate of 0.08h$^{-1}$ under the optimum conditions with carrier volume of 55% and aeration rate of 3 vvm.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2004.05a
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• pp.384-387
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• 2004

The purpose of the present investigation was to develop a novel method for cell immobilization. Aureobasidium pullulans cells were mixed with an alginate solution, and the mixture was extruded to form small gel beads as hydrated- immobilized cells. The beads were then placed at $-15^{\circ}C$ for 6-24 h to induce freeze-dehydration. The freeze-dehydration resulted in shrinkage of beads due to water removal reducing bead volume by 82% and bead weight by 85%. The dehydrated beads were successfully used for the production of fructo-oligosaccharides in a model reactor system. This study showed that bioreactor performance can be improved up to 2 times by the use of the dehydrated beads.

• Journal of Microbiology
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• v.44 no.3
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• pp.354-359
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• 2006

This study examined the capacity of immobilized bacteria to degrade petroleum hydrocarbons. A mixture of hydrocarbon-degrading bacterial strains was immobilized in alginate and incubated in crude oil-contaminated artificial seawater (ASW). Analysis of hydrocarbon residues following a 30-day incubation period demonstrated that the biodegradation capacity of the microorganisms was not compromised by the immobilization. Removal of n-alkanes was similar in immobilized cells and control cells. To test reusability, the immobilized bacteria were incubated for sequential increments of 30 days. No decline in biodegradation capacity of the immobilized consortium of bacterial cells was noted over its repeated use. We conclude that immobilized hydrocarbon-degrading bacteria represent a promising application in the bioremediation of hydrocarbon-contaminated areas.

• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.303-309
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• 1985

Continuous production of hydrogen by Ca alginate-immobilized photosynthetic bacteria was studied in a packed-bed bioreactor. The dilution rate and input concentration of carbonaces substrate were selected as operating parameters. To choose the strain for immobilization, hydrogen productivities of Rhodopseudomonas caposulata 10006 and Rhodospirillum rubrum KS-301 were compared through preliminary batch cultures of their free cells: the former was found to show better hydrogen productivity in spite of its lower specific growth rate. For the continuous production of hydrogen by immobilized R capsulata, the optimum dilution rate was about 0.84 h$^{-1}$ . The Immobilized tells gave better hydrogen yield and conversion efficiency than free ones. And a kinetic parameter K'$_{m}$ was determined for the packed-bed bioreactor, being practically constant for a specific range of dilution rates.s.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.326-332
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• 2018

In this study,the result shows that polyvinyl alcohol-sodium alginate (PVA-SA) gel bead crosslinked with sodium sulfate are better among the different methods by comparing the relative mechanical strength, mechanical strength swelling and expansion coefficient of beads in water. Subsequently, anammox biomass entrapment by PVA-SA gel was introduced into continuous stirred tank reactor (CSTR). After 24 operation days, the nitrogen removal efficiency achieved 60%, while the nitrogen loading rate (NLR) was $0.14kgN/m^3/d$ and the experiment data indicated that PVA-SA gel bead crosslinked with sodium sulfate can be used to initiate anammox process. Furthermore, it is an alternative for culturing anammox in a long-term operation.