• KSBB Journal
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• v.25 no.2
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• pp.155-166
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• 2010

Studies on the production of cell-wall bound innerpolysaccharides (IPS) (soluble ${\beta}$-D-glucan) have been performed by use of suspended myelial cultures of Inonotus obliquus. This product has promising potentials as an effective antidiabetic as well as an immunostimulating agents. As a first step to enhanced production of IPS, Intensive strain improvement programs were carried out by obtaining a large amounts of protoplasts for the isolation of single cell colonies. Rapid and large screening of high-yielding producers was possible because about fivefold higher amount of protoplasts ($2.3{\times}10^6$ protoplasts/mL) could be recovered with relatively high regeneration rates of $10^{-2}{\sim}10^{-3}$ by applying a modified filtration method, as compared to the previously used trapping method. A basic protocol necessary for UV-mutation of the protoplasts was also developed, resulting in several overproducing variants with good fermentation properties. Since the amount of IPS extracted from the mycelial cell walls of I. obliquus turned out to be almost constant per g DCW, increase in cell mass was considered the most important factor for the enhancement in IPS production. Therefore, attempts were made to screen mutant cells showing rapid mycelial growth rate in the final suspended cultures. Notably, the mutant strains showing an active cellgrowth in the preceding solid growth cultures were observed to produce higher amount of IPS in the suspended fermentations as well. A striking mutant, OBLQ756-15-5 strain, obtained from the survivors of a harsh UV-treated condition (97% death rate) was found to stably produce as high cell mass as 22 g DCW/L in the final fermentations. Currently, this strain is being tested for development of a scaled-up fermentation process for mass production of IPS.

• Journal of Life Science
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• v.29 no.1
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• pp.76-83
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• 2019

In this study, the optimal growth and poly(3-hydroxybutyrate) (PHB) biosynthesis of Pseudomonas sp. EML2 were established using waste frying oil (WFO) as a cheap carbon source. The fatty acid composition of WFO and fresh frying oil (FFO) were analyzed by gas chromatography. The unsaturated and saturated fatty acid contents of the FFO were 82.6% and 14.9%, respectively. These contents changed in the WFO. The compositional change in the unsaturated fatty acid content in the WFO was due to a change in its chemical and physical properties resulting from heating, an oxidation reaction, and hydrolysis. The maximum dry cell weight (DCW) and PHB yield (g/l) of the isolated strain Pseudomonas sp. EML2 were confirmed under the following culture conditions: 30 g/l of WFO, 0.5 gl of $NH_4Cl$, pH 7, and $20^{\circ}C$. Based on this, the growth and PHB yield of Pseudomonas sp. EML2 were confirmed by 3 l jar fermentation. After the cells were cultured in 30 g/l of WFO for 96 h, the DCW, PHB content, and PHB yield of Pseudomonas sp. EML2 were 3.6 g/l, 73 wt%, and 2.6 g/l, respectively. Similar results were obtained using 30 g/l of FFO as a carbon source control. Using the FFO, the DCW, PHB content, and PHB yield were 3.4 g/l, 70 wt%, and 2.4 g/l, respectively. Pseudomonas sp. EML2 and WFO may be a new candidate and substrate, respectively, for industrial production of PHB.

• Microbiology and Biotechnology Letters
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• v.37 no.3
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• pp.197-203
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• 2009

An indole oxygenase originated from Rhodococcus sp. RHA1 was cloned into the expression vector, pTrc99A, in Escherichia coli, and designated pTCAN1. The pTCAN2 was constructed from pTCAN1 by the deletion of $lacI^q$ for the constitutive expression of indole oxygenase without adding IPTG in the medium. The complete open reading frame of indole oxygenase was 1,224 bp long, which encodes a protein of 407amino acids. Crude extracts of E. coli $DH5{\alpha}$/pTCAN1 and pTCAN2, respectively, were prepared and subjected to SDS-PAGE analysis. A band corresponding to molecular mass of about 43 kDa was appeared and this result correlated with the predicted molecular mass of cloned indole oxygenase. The E. coli harboring pTCAN1 and pTCAN2, respectively, showed blue color colony in LB plate. The pigment showing blue color was prepared from E. coli $DH5{\alpha}$/pTCAN2, and identified as indigo by experiments using spectrophotometer, HPLC, and TLC. The indigo-forming activity of indole oxygenases from the whole cell of E. coli $DH5{\alpha}/pTCAN1$ cultured at LB medium added 1mM of IPTG and that of E. coli/pTCAN2 showed about 1.75nmol/min/mg DCW (dry cell weight) and 3.85 nmol/min/mg DCW, respectively. Also, the E. coli $DH5{\alpha}$/pTCAN2 produced about $236{\mu}M$ of indigo after 48 hours incubation in TB medium supplemented with 2.5 mM of tryptophan.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3799-3804
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• 2014

In sea water, microalgae are exposed to a range of critical environmental conditions. Microalgae are protected from UV-A radiation due to the presence of mycosporine like amino acids(MAAs). Owing to the UV-A absorption properties of MAAs, they are used widely as a UV protecting ingredient in cosmetics. Therefore, there is a need to increase the production yield of MAAs. This study investigated the production yield of MAAs in transformed microalgae by radiofrequency(RF) exposure. Initially, the Glut-1 gene was transformed to Chlamydomonas hedleyi microalgae as a glucose transporter. The biomass was enhanced after Glut-1 gene transformation. In addition, the MAAs production yield was increased during large scale production in bioreactors due to the RF treatment. Therefore, purified extracts of MAAs can be used as a sun block material in the cosmetic industrial field.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.419-424
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• 2018

In this work, effect of the culture medium composition on the fermentation process of Clostridium ljungdahlii, which is acetogenic bacteria to product ethanol from synthesis gas, was examined to improve the microbial growth and ethanol production. Components of the culture medium such as yeast extract, fructose, $NH_4Cl$, and $K_2HPO_4$ were selected as influence factors for the cell growth and ethanol production. As the concentration of yeast extract increased, both of the cell growth and ethanol production increased. And the ethanol productivity was the highest at an yeast extract of 0.05 g/L, which is lower than that of base medium. As the concentration of fructose increased, the cell growth increased, but the ethanol production decreased when the concentration of fructose was higher than that of base medium (5 g/L). In an experiment with the yeast extract of 5 g/L, produced ethanol concentration was the highest (0.297 g/L) when fructose concentration was 5 g/L, however, the specific ethanol productivity was higher (0.281 g/g DCW) when the fructose was not added due to very low cell mass. The cell growth and ethanol production were not significantly influenced by $NH_4Cl$ concentration, however the growth inhibition was observed at a 30 g/L of $NH_4Cl$. When the concentration of $K_2HPO_4$ increased, both of the cell growth and ethanol production increased. In experiments with $NH_4Cl$ and $K_2HPO_4$, specific ethanol productivities were higher when the low concentration of yeast extract was used.

• Journal of Life Science
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• v.18 no.12
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• pp.1764-1770
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• 2008

The goal of this study is to increase production of astaxanthin in recombinant Escherichia coli by engineered isoprenoid pathway. We have previously reported structural and functional analysis of the astaxanthin biosynthesis genes from a marine bacterium, Paracoccus haeundaensis. The carotenoid biosynthesis gene cluster involved in astaxanthin production contained six carotenogenic genes (crtW, crtZ, crtY, crtI, crtB, and crtE genes) and recombinant E. coli harboring six carotenogenic genes from P. haeundaensis produced 400 ${\mu}g$/g dry cell weight (DCW) of astaxanthin. In order to increase production of astaxanthin in recombinant E. coli, we have cloned 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (lytB), farnesyl diphosphate (FPP) synthase (ispA), and isopentenyl (IPP) diphossphate isomerase (idi) in the isoprenoid pathway from E. coli and coexpressed these genes in recombinant E. coli harboring the astaxanthin biosynthesis genes. This engineered E. coli strain containing both isoprenoid pathway gene and astaxanthin biosynthesis gene cluster produced 1,200 ${\mu}g$/g DCW of astaxanthin, resulting 3-fold increased production of astaxanthin.

• Korean Journal of Microbiology
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• v.38 no.1
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• pp.26-30
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• 2002

A ubiquitous bacterium,Effects of Lead, Copper and Cadmium on Pseudomonas cepacia KH410 Isolated from Freshwater Plant Root was isolated from freshwater plant root and interactions of lead, copper and cadmium with this strain was studied. Mass production of dry cell weight 2.72 g-DCW/ι-medium was obtained by cultivation in a nutrient medium containing 1% yeast extract, 1% soytone and 0.5% NaCl, pH 7.0, at temperature of 28℃ for 24 hrs under aeration. The mass of dry cell produced after exposure with 100 mg/ι of heavy metal was 1.98 g/ι for lead, 1.58 g/ι for copper and 0.20 g/ι for cadmium, respectively. The minimal inhibitory concentrations (MIC) for each heavy metal was 1.3 mM for lead,0.8 mM for copper and 0.4 mM fur cadmium, respectively. Cell aggregation occurred by each heavy metal exposure was observed from 1 day to 4 days by an optical microscope. Entrapment, precipitation effects on cell by heavy metals between 10 min and two hours were examined by an electron microscopy. Cadmium appeared to be the most toxic on cells and the order of toxicity was cadmium>copper>lead.

• Korean Journal of Microbiology
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• v.37 no.1
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• pp.92-99
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• 2001

High-cell-density cultivation of Ralstonia eutopha KHB 8862 by fed-batch fermentation in a 200 l pilot plant was carried out for the mass production of poly(3-hydroxybutyrate) (PHB). After 80 h of cultivation, the dry cell weight (DCW), PHB concentration, and PHB yield from fructose syrup reached 168 g/l, 74%DCW, and 0.27 (w/w), respectively, resulting in a productivity of 1.6 g of PHB/L/h. Based on these results, the PHB production cost from bacterial fermentation was analyzed and economic evaluation was performed. In the case of new investment being implemented or not, the production cost of PHB was US$ 3.15/kg and US$ 2.41/kg, respectively. PHB productivity and PHB yield on a carbon substrate were both important factors to be optimized. The increase of PHB yield on a carbon sources significantly decreased the PHB production cost but the increase in productivity had a relatively slight effect on the decrease in PHB production cost because the cost of carbon sources (37%) for PHB was larger in proportion to total cost than the depreciation cost (17%). These results suggest that the increased PHB yield from carbon sources and the development of new cheaper substrates would be more effective in decreasing PHB production cost than the increase in productivity. It was demonstrated that PHB is not in competition with consumable plastics such as PET in present market. Therefore, it is essential to lower production cost to be used as a bulk product and desirable to develop new application fields for PHB such as biomedical and cosmeceuticals.

• Microbiology and Biotechnology Letters
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• v.33 no.3
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• pp.215-221
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• 2005

It was characterized the hexane biodegradation and mineralization using a hexane-degrading consortium, and analyzed its bacterial community structure by 16S rDNA PCR-DGGE (denaturing gradient gel electrophoresis). The specific growth rate (${\mu}_{max}$) of the hexane-degrading consortium was 0.2 $h^{-1}$ in mineral salt medium supplemented with hexane as a sole carbon source. The maximum degradation rate ($V_{max}$) and saturation constant ($K_{s}$) of hexane of the consortium are 460 ${\mu}mol{\cdot}g-DCW^{-1}{\cdot}h^{-1}$ and 25.87 mM, respectively. In addition, this consortium could mineralize $49.1{\%}$ of $^{14}C$-hexane to $^{14}CO_2$, and $43.6{\%}$ of $^{14}C$-hexane) was used for the growth of biomass. The clones isolated from the DGGE bands were closely related to the bacteria which were capable of degrading pollutants such as oil, biphenyl, PCE, and waste gases. The hexane-degrading consortium obtained in this study can be applied for the biological treatment of hexane.

• KSBB Journal
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• v.21 no.2
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• pp.90-95
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• 2006

Escherichia coli harboring pAC-LYCO4 and pDdxs was used for lycopene production. Three wild type strains of E. coli OW1, MG1655, and W3110 were compared with DH5${\alpha}$ used before for lycopene production. Lycopene productivity of E. coli MG1655 was similar to DH5${\alpha}$ and the highest among those wild type strain. Therefore, MG1655 strain was used for random transposon and NTG mutagenesis to increase lycopene productivity. Through transposon mutation, five transposon mutants with increased lycopene productivity were obtained. It was found that genes knocked out by transposon insertion were treB in Tn1 mutant, B2436 in Tn2 mutant, and rfaH in Tn3, 4, and 5 mutants. Lycopene productivity was the highest in Tn4 mutant among the Tn mutants, which was 6-fold and 8-fold higher in lycopene concentration and content, respectively, in comparison with those obtained with wild type strain. NTG4 mutant was acquired with NTG mutation. The highest lycopene productivity of 6 mg/L and 4 mg/g DCW was obtained from the NTG4 mutant when arabinose of 0.013 mM was added for induction of dxs, rate-limiting gene of MEP pathway. The lycopene productivity of NTG4 mutant was increased 18-fold and 12-fold in lycopene concentration and content, respectively when comparing with the wild type strain.