• KSBB Journal
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• v.30 no.4
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• pp.161-165
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• 2015

Lactic acid and its derivatives are widely used in the food, pharmaceutical, and cosmetic industries. It is also a major raw material for the production of poly-lactic acid (PLA), a biodegradable and environmentally friendly polymer and a possible alternative to synthetic plastics derived from petroleum. For PLA production by new strains of lactic acid bacteria (LAB), we screened LAB isolates from shellfish. A total of 51 LAB were isolated from 7 types of shellfishes. Lactic acid production of individual isolates was examined using high-performance liquid chromatography using a Chiralpak MA column and an ultraviolet detector. Lactobacillus plantarum T-3 was selected as the most stress-resistant strain, with minimal inhibition concentrations of 1.2 M NaCl, 15% ethanol, and 0.0020% hydrogen peroxide. In a 1 L fermentation experiment, $\small{D}$-lactic acid production of 19.91 g/L fermentation broth was achieved after 9 h cultivation, whereas the maximum production of total lactic acid was 41.37 g/L at 24 h.

• Journal of Marine Bioscience and Biotechnology
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• v.11 no.2
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• pp.36-41
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• 2019

This study was conducted to analyze the difference in mechanically improved properties by distinguishing α-chitin and β-chitin for Poly(L-lactic acid)(PLLA). First, dissolution of chitins was established by mixing polar solvents hexafluoroisopropanol (HFIP) and trifluoroacetic acid (TFA) in appropriate proportions. Under these conditions, the dissolved chitin was used for electrospinning with other polymers. The electrospun nanofibers of the PLLA and chitins were successfully produced. Compared to the pristine state, when chitin was added to PLLA, the tensile strength increased 1.41 times (α-chitin), by 1.61 times (β- chitin), respectively. Based on this, it was confirmed that α- and β- chitin could be strategically used for different polymers. The results also suggest that chitin can be applied to various fields as good reinforcing material as well as electrospinning.

• Microbiology and Biotechnology Letters
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• v.31 no.3
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• pp.250-256
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• 2003

Lactic acid bacteria with amylolytic and acid producing activities can ferment starch directly to lactic acid thereby producing a monomer for the production of biodegradable poly lactic acid (PLA). In this study, the strain producing L-lactic acid from soluble starch was isolated from Nuruk. The isolated strain was identified as Enterococcus sp. through its morphological, cultural, biochemical characteristics as well as the 16S rDNA sequence analysis, and named Enterococcus sp. JA-27. Enterococcus sp. JA-27 produced exclusively L-lactic acid from soluble starch as a carbon source. The optimal conditions for the maximum production of L-lactic acid from Enterococcus sp. JA-27 were 30 C, pH 8, 1.5 % soluble starch as a substrate and 3.5 % tryptone as a nitrogen source, 0.1 % $K_2$$HPO_4$, 0.04 % $MgSO_4$. $7H_2$O, 0.014 % $MnSO_4$$.$4$H_2O$, 0.004% $FeSO_4$$.$$7H_2$O. Batch and fed batch culture were carried out and the former was more effective. L-Lactic acid production in the optimum medium was significantly increased in a 7 L jar fermenter, where the maximum L-lactic acid concentration was 3 g/L. For the purification of lactic acid in fermented broth, two stage ionexchange column chromatographies were employed and finally identified by HPLC.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.461-468
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• 2018

Microspheres were prepared by solvent-evaporation method with Poly-L-lactic acid (PLLA) as a starting material, and the effects of preparation variables on microsphere shape and average particle size were investigated. As the concentration of PVA solution increased from 1 to 5 wt%, the average particle size decreased from $370{\mu}m$ to $160{\mu}m$ and then increased to $240{\mu}m$ at 7 wt%. On the other hand, As the addition volume of PVA solution increased from 10 mL to 50 mL, the average particle size decreased from $370{\mu}m$ to $220{\mu}m$. Also, as the stirring speed increased from 500 rpm to 1,500 rpm, the average particle size decreased from $370{\mu}m$ to $110{\mu}m$. When dichloromethane and chloroform were used as organic solvents, respectively, the average particle size did not show any significant difference. However, when dichloromethane was used, voids were observed on the particle surface, but when chloroform was used, smooth spherical particles were obtained.

• Polymer(Korea)
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• v.24 no.3
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• pp.431-436
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• 2000

To improve the thermal and mechanical properties of homo poly(L-lactic acid), DL-mandelic acid, one of the natural $\alpha$-hydroxy acid with aromatic ring as the side-chain residue was used as the comonomer. Copolymers with different contents of mandelic acid were prepared and characterized. The resulting copolymers were mostly amorphous. As the amount of mandelic acid in the monomer feed increased, the molecular weight of the resulting polymers tended to decrease linearly. T$_{g}$ and T$_{d}$ of the copolymer, however, were found to shift toward higher temperature, suggesting the improved thermal stability by increasing content of mandelic acid moiety. Tensile measurements of cast films showed somewhat improved values in the copolymers with mandelic acid content of 5 and 10 wt%.%.%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.3
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• pp.104-109
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• 2023

Electrospinning was performed using an eco-friendly solvent composed of acetic acid, ethyl acetate and distilled water to investigate the effect of gelatin concentration on mechanical properties and cytotoxicity of absorbable poly(D,L-lactic acid) (PDLLA)/gelatin blend membrane. The tensile stress, strain at break, and WUC of the PDLLA/gelatin (97/3) scaffold at 26 wt% concentration were determined to be 3.9 ± 0.7 MPa, 37 ± 1.3 %, and 273 ± 33 %, respectively. FT-IR results revealed that PDLLA and gelatin were bound only by van der Waals interactions. The cell viability of PDLLA/gelatin membranes containing 0 %, 1 %, 2 %, 3 %, and 4 % gelatin were more than 100 %, which makes all membranes highly suitable as a barrier membrane for absorbable periodontal tissue regeneration due to their marketed physical properties and biocompatibility.

• Macromolecular Research
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• v.9 no.2
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• pp.84-91
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• 2001

Both A-B-A triblock and multiblock copoly(ester-ether)s consisting of poly(L-Lactide) and poly(oxyethylene-co-oxypropylene) were prepared and characterized. The preparation of the triblock copolymer was done by ring-opening copolymerization of L-lactide with a commercially available telechelic copolyether, Pluronic$\^$TM/(PN) by catalysis of stannous octanoate. The molecular weight and unit composition of the produced copolymers were successfully controlled by changing the L-lactide/PN ratio in feed. However, a high molecular weight copolymer incorporating PN in large amount was not obtained because the molecular weight of the resulting copolymer was limited at a high L-lactide/PN composition. The multiblock copolymer was synthesized by the copolycondensation of oligo(L-lactic acid) prepared by thermal dehydration of L-lactic acid, PN, and dodecanedioic acid as carboxyl/hydroxyl adjusting agent. This polycondensation proceeded by catalysis of stannous oxide to give multiblock copolymers with high molecular weight and wide range of compositions.

• Polymer(Korea)
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• v.29 no.1
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• pp.69-73
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• 2005

To overcome the main disadvantages of non-viral gene delivery systems such as repeated administration due to the low transfection efficiency, poly(D,L-lactide-co-glycolide) was applied to encapsulate pDNA in its microsphere formulation. Free pDNA or various ratios (w/w) of chitosan/pDNA complexes was used for encapsulation, with the resulting encapsulation efficiency of 44%, 5%, and 8% for free pDNA, 0.7:1 and 1:1 ratios, respectively. Scanning electron micrographs of poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres encapsulating pDNA or chitosan-condensed pDNA revealed a smooth spherical shape immediately after microsphere preparation and a collapsed porous shape in 41 days due to the degradation of PLGA. In vitro release profile showed that the 0.7:1 (w/w) ratio formulation exerted 47% release in 26 days, whereas free pDNA or 1:1 (w/w) ratio formulation did only 15% or 32%, respectively.

• Advanced Composite Materials
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• v.16 no.4
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• pp.259-267
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• 2007

Mechanical reinforcement of an all-sustainable composite, composed of papyrus stem-milled particles as reinforcement and poly-L-lactic acid (PLLA) resin as matrix, was investigated. The papyrus particles (average diameter of $70{\mu}m$) could be well dispersed in PLLA resin up to 50 wt% without any surface modification. Young's modulus of the composite was 4.2 GPa at 50 wt% of the papyrus content. This is a two-fold increment in modulus as compared to that of the PLLA matrix. The tensile strength of the composite was almost constant around 48 MPa irrespective of the papyrus content. Temperature dependence of the storage modulus demonstrated that the incorporation of papyrus restricts the large drop in the modulus above the glass transition of PLLA.

• Medical Lasers
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• v.10 no.3
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• pp.181-184
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• 2021

Scars can cause great psychological stress among patients. Currently, there are numerous topical agents, laser and surgical treatments available for skin rejuvenation and scar minimization. Laser-assisted drug delivery (LADD) is a treatment method that increases drug delivery by stimulating the skin physically and chemically to enhance the penetration of topical agents. This is one of the areas of great interest in the treatment of various skin diseases in addition to its use for cosmetic purposes. In particular, LADD is relatively non-invasive and has advantages in terms of accessibility and stability. Poly-L-lactic acid (PLLA) is a collagen stimulator known to gradually restore skin volume by inducing inflammation and fibroplasia. Herein, we report a case of treatment of an atrophic scar with fractional carbon dioxide laser-assisted PLLA delivery.