• Metals and materials international
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• v.24 no.6
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• pp.1346-1358
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• 2018

A novel additive manufacturing method with TIG-MIG hybrid heat source was applied for fabricating 5356 aluminum alloy component. In this paper the microstructure evolution, mechanical properties and fracture morphologies of both as-deposited and heat-treated component were investigated, and how these were affected by different heat-treated temperature. The as-deposited microstructure showed dominant equiaxed grains with second phase, and the size of them is coarse in the bottom region, medium in the middle region and fine in the top region owing to different thermal cycling conditions. Compared with as-deposited microstructure, the size of grain becomes large and second phases gradually dissolve in the matrix as heat-treated temperature increase. Different microstructures determine the mechanical properties of component. Results show that average ultimate tensile strength enhances from 226 to 270 MPa and average microhardness increases from 64.2 to 75.3 HV0.1 but ductility decreases from 33 to 6.5% with heat-treated temperature increasing. For all components, the tensile properties are almost the same in the vertical direction (Z) and horizontal direction (Y) due to equiaxed grains, which exhibits isotropy, and the mechanisms of these are analyzed in detailed. In general, the results demonstrate that hybrid arc heat source has the potential to fabricate aluminum alloy component.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.195-202
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• 2023

Protease is a widely used enzyme particularly in the detergent industry. In this research, we aimed to isolate alkaline protease-producing bacteria for characterization as a laundry detergent additive. The screening of alkaline protease production was investigated on basal medium agar plus 1% skim milk at pH 11, with incubation at 30℃. The highest alkaline protease-producing bacterium was 6BS15-4 strain, identified as Bacillus gibsonii by 16S rRNA gene sequencing. While the optimum pH was 12.0, the strain was stable at pH range 7.0-12.0 when incubated at 45℃ for 60 min. The alkaline protease produced by B. gibsonii 6BS15-4 using dairy effluent was characterized. The optimum temperature was 60℃ and the enzyme was stable at 55℃ when incubated at pH 11.0 for 60 min. Metal ions K⁺, Mg²⁺, Cu²⁺, Na⁺, and Zn²⁺ exhibited a slightly stimulatory effect on enzyme activity. The enzyme retained over 80% of its activity in the presence of Ca²⁺, Ba²⁺, and Mn²⁺. Thiol reagent and ethylenediaminetetraacetic acid did not inhibit the enzyme activity, whereas phenylmethylsulfonyl fluoride significantly inhibited the protease activity. The alkaline protease from B. gibsonii 6BS15-4 demonstrated efficiency in blood stain removal and could therefore be used as a detergent additive, with potential for various other industrial applications.

• Microbiology and Biotechnology Letters
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• v.26 no.3
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• pp.200-205
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• 1998

A probiotic-strain of Lactobacillus sp. was cultured in bovine blood plasma-based (BBPB) medium and freeze-dried to prepare a probiotic product as an animal feed additive. The cell mass produced in the medium, $5.2{\times}10^9$ CFU/ml, was high enough to be commercialized and was 74% of that in MRS medium. The survival rate of tactobacillus sp. against freeze-drying was affected by the conditions for treatment of cultured BBPB broth before freeze-drying such as pH adjustment, volume reduction and freezing rate. It was also found that the blood protein hydrolysate remaining in broth also enhanced the survival rate. Among various protective substances, sucrose showed a high stabilizing effect with 10% (w/v) addition, by which the maximum survival rate (48.3%) and viable cell count ($3.0{\times}10^{10}$ CFU/g) were obtained.

• The Korean Journal of Mycology
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• v.21 no.4
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• pp.310-315
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• 1993

Phanerochaete chrysosporium is a white rot fungus which secrets a family of lignin-degrading enzymes under nutrient limitation. Ligninase was extracellularly produced in agitated submerged cultures of P. chrysosporium, SC 26. Addition of veratryl alcohol(4 mM), and benzyl alcohol(10 mM) with 0.1% Tween 20 to the culture medium stimulated ligninase production. However, ligninase was not detected when both treatments of veratryl alcohol and benzyl alcohol without Tween 20 were added to the medium. Addition of 0.1 % Tween 20 to the culture medium had little effect on ligninase activity. The ligninase activity was maximum on day 5-8 for veratryl alcohol, and benzyl alcohol with 0.1 % Tween 20 additive medium.

• Proceedings of the KSAR Conference
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• 2003.06a
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• pp.79-79
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• 2003

Embryonic stem cells are capable of differentiating into a variety of cell lineages. However, the ultimate results of differentiation in vitro greatly depend on the duration of treatment and kinds of differentiating inducers added. In order to investigate the efficiencies of various differentiation inducers and the methods of treatment, we examined differentiation patterns of human embryonic stem cell (hESC, MB03) according to several different protocols. Exp. I) Upon differentiation using retinoic acid and ascorbic acid (RA/AA), embryoid bodies (EB, for 4days) derived from hESC was exposed to Rh (10$^{-6}$ M) and AA (50 mM) for 4 days, and were allowed to differentiate in N2 medium for 7, 14, 21, or 28 days. Exp. II) When bFGF was used, neuronal precursor cells were selected for 8 days in N2 medium after EB formation. After selection, cells were expanded at the presence of bFGF (20 ng/ml) for another 6 days followed by a final differentiation in N2 medium for 7, 14, 21 or 28 days. Exp. III) In addition, to examine the effects of neurotrophic factors in the production of mature neurons, groups of cells were exposed to either BDNF (5 ng/ml) or TGF-$\alpha$(10 ng/ml) during the 28 days of final differentiation. Differentiation patterns of RA/AA or bFGF treated groups were very similar; approximately 82% and 83% of the cells, respectively, were positive for anti-NF200 antibody, while it was about 10% and 11%, respectively, for anti-NF160 antibody in 28 days in N2 medium. Alsor, cells expressing TH were as low as 5%, while the cells doubled when matured at the presence of either BDNF or TGF-$\alpha$. Cells immunoreactive to anti-GAD antibody were approximately 20%. These results suggest that a maturation step rather than differentiation induction step, which is formation of EB, effects more decisively to the ultimate differentiation pattern.

• Research in Plant Disease
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• v.11 no.1
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• pp.66-71
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• 2005

The effect of medium components such as wheat bran, rice bran, oat meal, and soybean meal as basic ingredients and KH2PO4, glucose, and molasses as additives on mass production and anti-potato common scab activ ity of a streptomycete A020645 strain as a biocontrol agent (BCA) candidate was investigated. Of basicingredients, oat meal was the best one for mass poduction and enhancement of anti-potato common scabactivity. The biomass production of the active strain was more enhanced when 0.1-0.01.% glucose or molassesas additive were added into the basic medium. These information may have important implications in applying for effective formulation of BCA.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.529-532
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• 2001

Korean food waste, one of the abundantly available but environmentally problematic organic wastes in Korea, was utilized as solid-substrate by fungal strain Aspergillus niger ATcC 6275 for the production of enzymemixture containing amylase, cellulase and xylanase. The enzyme mixture can be used as high value-added animal feed. Solid-state fermentation method yielded a 84-fold enhancement in xylanase activity compared with submerged fermentation method. The effect of incubation period, incubation temperature, pH of medium, moisture content, inoculum size and enrichment of the medium with nitrogen and carbon sources were observed for optimal production of these enzymes The optimal amylase activity of 33.10 U/g, cellulase activity of 24.41 U/g, xylanase activity of 328.84 U/g were obtained at 8 days incubation with 50%(w/w) soy bean flake, with incubation temperature of $25^{\circ}C$, pH of 6.38, optimal moisture content of 55% and with inoculum size of $3.8{\times}10^6$spore/g. Enzyme activities were enhanced when ImM $CaSO_4$, 2% Malt extract and 2% galactose were added as mineral, nitrogen and carbon enrichment respectively.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.358-365
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• 2020

An organic solvent- and bleach-stable protease-producing strain was isolated from a polluted river water sample and identified as Aeromonas veronii OB3 on the basis of biochemical properties (API 20E) and 16S rRNA sequence analysis. The strain was found to hyper-produce alkaline protease when cultivated on fish waste powder-based medium (HVSP, 4080 U/ml). The biochemical properties and compatibility of OB3 with several detergents and additives were studied. Maximum activity was observed at pH 9.0 and 60℃. The crude protease displayed outstanding stability to the investigated surfactants and oxidants, such as Tween 80, Triton X-100, and H₂O₂, and almost 36% residual activity when incubated with 1% SDS. Remarkably, the enzyme demonstrated considerable compatibility with commercial detergents, retaining more than 100% of its activity with Ariel and Tide (1 h, 40℃). Moreover, washing performance of Tide significantly improved by the supplementation of small amounts of OB3 crude protease. These properties suggest the potential use of this alkaline protease as a bio-additive in the detergent industry and other biotechnological processes such as peptide synthesis.

• Korean Journal of Agricultural Science
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• v.38 no.3
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• pp.473-477
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• 2011

A number of health benefits have been claimed for probiotic bacteria such as Bifidobacterium (B) spp. Lactobacillus(L) acidophilus, and Lactococcus(Lc) cremoris. Viability of probiotic bacteria is important in order to provide health benefits. Only a limited culture media for the test purpose of probiotic bacteria are commercially available (MRS broth), but the media for large-scale propagation of viable cells which are able to be used as food additive are not available. The manufacture of a low priced and preferred novel medium for probiotic bacteria was therefore, attempted using whey protein concentrate(WPC) and Makgeolli sludge as a starting material. The effect of WPC and Makgeolli sludge on the growth of four strains (B. bifidum 15696, B. longum 15707, L. acidophilus CH-2, and Lc. cremoris 20076) was investigated. Medium prepared such as WPC, Makgeolli sludge, and WPC+Makgeolli sludge(WPCMs). It was observed that the growth of 4 strains (B. bifidum 15696, B. longum 15707, L. acidophilus CH-2, and Lc. cremoris 20076) was stimulated by Makgeolli sludge, WPC, WPCMs. Especially, Viable cell number of 4 strains in the WPCMs were higher than that of the single media. These result suggest the possibility that Makgeolli and WPC, acts as a growth factor for the growth of probiotic bacteria.

• Mycobiology
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• v.37 no.1
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• pp.43-47
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• 2009

The levels of ergothioneine (ERG), which have been shown to act as an excellent antioxidant, were determined in both fruiting bodies and mycelia of various mushroom species. We found that ERG accumulated at different levels in fruiting bodies of mushrooms and showed up to a 92.3-fold difference between mushrooms. We also found that ERG accumulated at higher levels in mycelia than in fruiting bodies of economically important mushroom species such as Ganoderma neo-japonicum, G. applanatum and Paecilomyces tenuipes. The addition of 2 mM methionine (Met) to mycelial culture medium increased the ERG contents in most mushroom species tested, indicating that Met is a good additive to enhance the ERG levels in a variety of mushroom species. Taking these results into consideration, we suggest that the addition of Met to the mycelial culture medium is an efficient way to enhance the antioxidant properties in economically important mushroom species.