• Journal of Microbiology and Biotechnology
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• v.23 no.8
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• pp.1070-1075
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• 2013

Streptococcus mutans is the primary etiological agent of dental caries. The antimicrobial peptide $\small{D}$-Nal-Pac-525 was designed by replacing the tryptophans of the Trp-rich peptide Pac-525 with $\small{D}$-${\beta}$-naphthyalanines. To assess the effect of $\small{D}$-Nal-Pac-525 on cariogenic bacteria, the activity of $\small{D}$-Nal-Pac-525 on the growth of S. mutans and its biofilm formation were examined. $\small{D}$-Nal-Pac-525 showed robust antimicrobial activity against S. mutans (minimum inhibitory concentration of 4 ${\mu}g/ml$). Using scanning electron microscopy and transmission electron microscopy, it was shown that $\small{D}$-Nal-Pac-525 caused morphological changes and damaged the cell membrane of S. mutans. $\small{D}$-Nal-Pac-525 inhibited biofilm formation of S. mutans at 2 ${\mu}g/ml$. The results of this study suggest that $\small{D}$-Nal-Pac-525 has great potential for clinical application as a dental caries-preventing agent.

• Journal of Environmental Science International
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• v.15 no.6
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• pp.513-525
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• 2006

In recent decades, biofiltration has been widely accepted for the treatment of contaminated air stream containing low concentration of odorous compounds or volatile organic compounds (VOCs). In this study, conventional biofilters packed with flexible synthetic polyurethane (PU) foam carriers were operated to remove toluene from a contaminated air stream. PU foams containing various amounts of pulverized activated carbon (PAC) were synthesized for the biofilter media and tested for toluene removal. Four biofilter columns were operated for 60 days to remove gaseous toluene from a contaminated air stream. During the biofiltration experiment, inlet toluene concentration was in the range of 0-150 ppm and EBRT (i.e., empty bed residence time) was kept at 26-42 seconds. Pressure drop of the biofilter bed was less than 3 mm $H_2O/m$ filter bed. The maximum removal capacity of toluene in the biofilters packed with PU-PAC foam was in the order of column II (PAC=7.08%) > column III (PAC=8.97%) > column I (PAC=4.95%) > column IV (PAC=13.52%), while the complete removal capacity was in the order of column II > column I > column III > column IV. The better biofiltration performance in column II was attributed to higher porosity providing favorable conditions for microbial growth. The results of biodegradation kinetic analysis showed that PU-PAC foam with 7.08% of PAC content had higher maximum removal rate ($V_m$=14.99 g toluene/kg dry material/day) than the other PU-PAC foams. In overall, the performance of biofiltration might be affected by the structure and physicochemical properties of PU foam induced by PAC content.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2818-2824
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• 2014

Trp residue is considered as one of the important constituents in antimicrobial peptides (AMPs) as it presence secured good activities in many cases. However, it is preferable to be changed because of their sensitivity towards light. We have synthesized the short Trp-rich AMP Pac-525 and its analogues to investigate the possibility of His(chx) as possible replacement analogue for Trp in AMPs. Based on the assay result of the antibacterial activity including anti-MRSA activity, His(chx) is considered as good candidate for the Trp replacement. Through these study, we found that His(chx) had several merits to design therapeutic antimicrobial agents compare to Trp in terms of i) increasing antibacterial activity without hemolytic activity, ii) successful in designing the short peptide (only four residues), iii) having anti-MRSA activity, iv) overcoming the light sensitivity. Furthermore, transmission electron microscopy (TEM) and dye leakage experiments suggested that P11 and P16 containing His(chx) kill bacteria via forming pore/ion channels on bacterial cell membranes.