• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.487-492
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• 1999

One of effective utilization method of rice husk is to utilize it as culture material by carbonizing the rice husk. As a second part of a series to investigate the effective and continuous production of carbonized rice husk by a cyclone combustor, a non-slagging vertical cyclone combustor without vortex collector pocket was introduced. Isothermal and mixed firing with LPG and rice husk were undertaken in order to characterize the system. Inert rice husk was used during the isothermal test to find mass of rice husk collected. It was impossible to ignite rice husk itself over the experimental conditions considered in this experiment. Cyclone combustor was operated at temperatures of 1,273~1,473K. Detailed combustion data were obtained from a pilot unit with the air flow rate of 70m$^3$/h and rice husk feed of 2kg. The equivalence ratio ranged from 0.66 to 3.48. The auxiliary gas flow rate was varied from 3.22 to 12.86$\ell$/min. The weight reduction, pH and particle size distribution of carbonized rice husk were measured to evaluate the quality of carbonized rice husk. An analysis of exhaust gas emission was conducted to characterize the combustor. The required carbonized rice husk could be obtained at equivalence ratio of 1.68~2.17, combustor temperature of 1,273~1,373K and auxiliary gas flow rate of 3.22~6.43$\ell$/min. A method to reduce CO emissions should be employed.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1004-1008
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• 2004

An extracellular acid phytase from Pseudomonas fragi Y9451 was purified to homogeneity from the culture supernatant by salting-out, DEAE-Sepharose column chromatography, CM-Sepharose column chromatography, and Sephacryl S-300 gel filtration. The molecular weight of the purified enzyme was estimated to be 74 kDa on gel filtration and 54 kDa and 25 kDa on SDS-PAGE, suggesting that the native enzyme was a heterodimeric protein. The purified enzyme was most active at pH 4.5 and $70^{\circ}C$ and fairly stable from pH 4.0- 6.0. It was specific for phytate and exhibited a $K_{m}$ value of 27 mM (sodium phytate, pH 4.5, $50^{\circ}C$). The phytase activity was strongly inhibited (at maximum by 87%) by $Fe^{3+},\;Cu^{2+},\;Fe^{2+}$, and $Zn^{2+}$ at 5 mM concentration, and greatly inhibited by $Ca^{2+}$ at 10 mM concentration. However, EDTA notably stimulated the phytase activity at 10 mM concentration. With optimum pH and stability, Pseudomonas fragi phytase could be a potential candidate for animal feed applications.

• Journal of Microbiology and Biotechnology
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• v.25 no.6
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• pp.880-886
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• 2015

Bacterial heme was produced from a genetic-engineered Escherichia coli via the porphyrin pathway and it was useful as an iron resource for animal feed. The amount of the E. coli-synthesized heme, however, was only few milligrams in a culture broth and it was not enough for industrial applications. To analyze heme biosynthetic pathways, an engineered E. coli artificially overexpressing ALA synthase (hemA from Rhodobacter sphaeroides) and pantothenate kinase (coaA gene from self geneome) was constructed as a bacterial heme-producing strain, and both the transcription levels of pathway genes and the intermediates concentrations were determined from batch and continuous cultures. Transcription levels of the pathway genes were not significantly changed among the tested conditions. Intracellular intermediate concentrations indicated that aminolevulinic acid (ALA) and coenzyme A (CoA) were enhanced by the hemA-coaA co-expression. Intracellular coproporphyrinogen I and protoporphyrin IX accumulation suggested that the bottleneck steps in the heme biosynthetic pathway could be the spontaneous conversion of HMB to coproporphyrinogen I and the limited conversion of protoporphyrin IX to heme, respectively. A strategy to increase the conversion of ALA to heme is discussed based on the results.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.972-981
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• 2009

In this paper, a fed-batch cultivation process in recombinant Escherichia coli BL21(DE3) bacteria, for the production of human soluble catechol-O-methyltransferase (hSCOMT), is presented. For the first time, a straightforward model is applied in a recombinant hSCOMT expression system and distinguishes an initial cell growth phase from a protein production phase upon induction. Specifically, the kinetic model predicts biomass, substrate, and product concentrations in the culture over time and was identified from a series of fed-batch experiments designed by testing several feed profiles. The main advantage of this model is that its parameters can be identified more reliably from distinct fed-batch strategies, such as glycerol pulses and exponential followed by constant substrate additions. Interestingly, with the limited amount of data available, the proposed model accomplishes satisfactorily the experimental results obtained for the three state variables, and no exhaustive process knowledge is required. The comparison of the measurement data obtained in a validation experiment with the model predictions showed the great extrapolation capability of the model presented, which could provide new complementary information for the COMT production system.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.398-404
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• 1991

- Ethanol production by calcium alginate-immobilized baker's yeast was studied in the continuous shaked-flask reactor (CSFR) using glucose medium as a feed. Immobilized cells were stable at 30~$37^{\circ}C$ and pH 4~8. Fermentation characteristics of immobilized baker's yeast were examined changing the initial glucose concentration employed were 50, 100 and 150 g/l, respectively. It was investigated that the influent glucose concentration and the dilution rate have an influence on the ethanol fermentation characteristics at steady state in continuous culture of immobilized baker's yeast. The optimum conditions for high ethanol productivity and low residual glucose output in ethanol prodution were shown to be 0.2 h ' for the dilution rate and 150 g/l for the influent glucose concentration. The maximum ethanol productivity, ethanol yield, specific growth rate and glucose conversion rate were around 7.12 g/$l\cdot h$, 0.23, 0.366 g/$l\cdot h$ and 78.43, respectively.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.725-730
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• 2003

Three recombinant Saccharomyces cerevisiae strains showing different levels of xylose reductase activity were constructed to investigate the effects of xylose reductase activity and glucose feed rate on xylitol production. Conversion of xylose to xylitol is catalyzed by xylose reductase of Pichia stipitis with cofactor NAD(P)H. A two-substrate fermentation strategy has been employed where glucose is used as an energy source for NADPH regeneration and xylose as substrate for xylitol production. All recombinant S. cerevisiae strains Yielded similar specific xylitol productivity, indicating that xylitol production in the recombinant S. cerevisiae was more profoundly affected by the glucose supply and concomitant It generation of cofactor than the xylose reductase activity itself. It was confirmed in a continuous culture that the elevation of the glucose feeding level in the xylose-conversion period enhanced the xylitol productivity in the recombinant S. cerevisiae.

• Research in Plant Disease
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• v.15 no.3
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• pp.262-265
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• 2009

The fungus gnat, Bradysia difformis was examined for its ability to transmit Fusarium oxysporum in PDA culture. Larvae and adults of B. difformis were able to transmit the fungus as ingested and sticking. We constructed GFP-expressed mutants with Fusarium oxysporum, then feed it to larvae of fungus gnat, B. difformis. So that mycelia were placed in the alimentary canal of larva.

• Korean Journal Plant Pathology
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• v.10 no.2
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• pp.129-135
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• 1994

Ninety-two isolates of Fusarium species were obtained from Chinese corn samples. The predominant Fusarium species isolated from corn seeds were F. moniliforme, F. proliferatum, F. oxysporum and F. subglutinans, and all 13 species were identified. Each isolate was grown on autoclaved wheat grains and wheat cultures were fed by twenty-one-day-old female rats for the toxicity test. Twenty-six out of 92 isolates caused the death accompanying feed refusal, severe weight loss, liver damage, and hemorrhages in the stomach and intestines. Of the toxigenic isolates, 17 isolates of F. moniliforme, 4 of F. oxysporum, 3 of F. proliferatum, and one of each F. sporotrichioides and unknown species were lethal to rats. The analyses of fumonisin B1 production of the 26 toxigenic Fusarium isolates were carried out by thin layer chromatography and high-performance liquid chromatography, and fumonisin B1 was confirmed by mass spectrometry. Fumonisin B1 was produced in wheat culture at levels ranging from 280 $\mu\textrm{g}$/g to 3,952 $\mu\textrm{g}$/g by all of toxigenic F. moniliforme and F. proliferatum, but by none of the other toxigenic Fusarium species. The present results suggest the high possibility of natural occurrence of fumonisin B1 in corn samples imported from China.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.939-946
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• 2012

Antibiotic production with Streptomyces sindenensis MTCC 8122 was optimized under submerged fermentation conditions by artificial neural network (ANN) coupled with genetic algorithm (GA) and Nelder-Mead downhill simplex (NMDS). Feed forward back-propagation ANN was trained to establish the mathematical relationship among the medium components and length of incubation period for achieving maximum antibiotic yield. The optimization strategy involved growing the culture with varying concentrations of various medium components for different incubation periods. Under non-optimized condition, antibiotic production was found to be $95{\mu}g/ml$, which nearly doubled ($176{\mu}g/ml$) with the ANN-GA optimization. ANN-NMDS optimization was found to be more efficacious, and maximum antibiotic production ($197{\mu}g/ml$) was obtained by cultivating the cells with (g/l) fructose 2.7602, $MgSO_4$ 1.2369, $(NH_4)_2PO_4$ 0.2742, DL-threonine 3.069%, and soyabean meal 1.952%, for 9.8531 days of incubation, which was roughly 12% higher than the yield obtained by ANN coupled with GA under the same conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.1
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• pp.109-115
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• 2023

Interspecific hybridization is a beneficial strategy in aquaculture. In this study, diploid hybrids were produced through interspecies hybridization of flounder Platichthys bicoloratus ♀ × starry flounder P. stellatus ♂, which became commercial within a year. These hybrids exhibited an advantage in growth ability, with female hybrids growing twice as large as males at 11 months. Furthermore, hybrid flounders exhibited faster growth rates than starry flounders and reciprocal hybrids. The average growth rate of hybrids was 1.37 and 1.18 times greater than that of starry flounder and reciprocal hybrids at 5.5 months, respectively; Additionally, feed efficiency was 1.21 and 1.10 times higher than that of the experimental groups. The experiments were conducted at five temperatures to determine the optimal fry production method. Six weeks of culture resulted in a significant temperature effect, with maximum growth at 27℃. However, over 90% of the males occurred in the groups at temperatures above 24℃. Therefore, the optimum temperatures for survival, growth, condition factor and frequency of the best-sized fingerling at 13 weeks of age were estimated at 21℃. Thus, hybrid flounders are of great potential for use in the flounder aquaculture industry.