This research was conducted to elucidate the optimum conditions for the antibacterial activity of konjak jelly using the evolutionary operation-factorial design technique. In the first set of experiments, concentration of a coagulation agent, soaking liquid, and temperature of water were set to 0.4%, 0.6×10－2 N, and 65℃ as a central point, respectively. The highest antibacterial activity was acquired at E21, in which the number of bacteria was 1.25 log cfu/g. Because the code of changes in the main effect was (-), it could be decided that the central point of the first set was not the optimum point. Although antibacterial activity in the second set was improved, the values of the main effect were higher than that of changes in the mean effect. The central point of third set was concentration of coagulation agent 0.8%, concentration of soaking liquid 1.0×10－2 N, and temperature of water 65℃. It was found that the antibacterial activity of central point in the third set was highest among all the tested set. Further, all the necessary conditions were appropriate to reach the optimum condition. The antibacterial activity of the central point in third set was more than 1,000 times higher than that of E11, in first set.

This study reports an environment-friendly synthetic strategy to process nickel oxide nanocrystals. A mesoporous nickel oxide nanostructure was synthesized using an environmentally benign biomimetic method. We used a natural rambutan peel waste resource as a raw material to ligate nickel ions to form nickel-ellagate complexes. The direct decomposition of the obtained complexes at 700 oC, 900 oC and 1100 oC in a static air atmosphere resulted in mesoporous nickel oxide nanostructures. The formation of columnar mesoporous NiO with a concentric stacked doughnuts architecture was purely dependent on the suitable direct decomposition temperature at 1100 oC when the synthesis was carried out. The prepared NiO nanocrystals were coated on cotton fabric and their antibacterial activity was also analyzed. The NiO nanoparticle-treated cotton fabric exhibited good antibacterial and wash durability performance.

Licorice and rosemary contain a number of natural phenolic compounds which have a strong antibacterial and antioxidant activity. Ulleungdo stonecrop (US, scientific name: Sedum takesimense Nakai), indigenous island, is also known as a good antibiotic agent and skin whitening agent and is regarded as a promising materials in cosmetics field. Although the antibacterial activity of each material have been reported, little is known about the effect of using them together. Therefore, the purpose of this study was to investigate the synergistic effect on antibacterial activity when licorice and rosemary extract and US were used together. Since licorice and rosemary are lipid soluble materials and US is water soluble material, oil in water (O/W) emulsion system was used for this study. To manufacture O/W emulsions containing three kinds materials, first licorice and rosemary extracts and US was dispersed in soy bean oil and phosphate buffer (pH7) respectively. Decaglyceryl laurate was used as an emulsifier. There was slight decrease (-0.09~-0.46 Δlog) in the number of bacteria when O/W emulsion containing 300ppm of each licorice and rosemary extracts was mixed into B.subtilis. However, adding US (2,700ppm) into aqueous phase caused the rapid decrease in the amount of bacteria to -1.71 ~ -2.96 Δlog which were much higher decrement than US only in normal emulsion (-1.64 Δlog). In particular, there was a noticeable synergistic effect when rosemary extract and US was used together. The results obtained from this study could provide useful information for utilizing licorice and rosemary extracts and US as functional materials in the food and cosmetic areas.

This study investigated the synergistic effects of a combination of cephalexin and gentamicin (CCG) against Streptococcus spp. isolated from bovine milk. Minimum inhibitory concentrations (MICs) and fractional inhibitory concentration (FIC) index were determined for 12 bacteria isolated from 12 bovine farms in Gyeongnam province. The MIC ranges of cephalexin, gentamicin and CCG were 0.25-0.5, 0.5-2.0 and 0.06-0.125 μg/mL, respectively. In addition, the FIC index range of CCG against the isolates was 0.32-0.34, showing a synergistic effect in the checkboard assay. In conclusion, CCG has a high antibacterial activity against Streptococcus isolates and may be utilized in the treatment of bovine streptococcal mastitis.

Polyurethane (PU) nanofibers containing graphene oxide (GO) and Ag doped functionalized reduced graphene oxide (Ag-RGO) were successfully prepared via the electrospinning technique. The uniform distribution of GO sheets along with Ag nanoparticle in the nanofibers was investigated by scanning electron microscopy and the elemental mapping technique. X-ray diffraction and thermal gravimetric analysis verified the presence of GO and Ag in the bicomposite nanofibrous mats. Antibacterial tests against Escherichia coli demonstrated that the addition of GO and Ag-RGO to the PU nanofiber greatly enhanced bactericidal efficiency. Overall, these features of the synthesized nanofibers make them a promising candidate material in the biomedical field for applications such as tissue engineering, wound healing, and drug delivery systems.

In order to establish symbiotic host-bacterial relationships, symbionts in insects evolved a mechanism to overcome host immune responses. Here we provide the resistance of symbiotic bacteria on the insect immune system. As a result, through the transposon mutagenesis, we found a salivary gland (SG) susceptible mutant. The disrupted gene was identified as nlpB involved in lipoprotein synthesis. The nlpB, bla double deletion mutant was sensitive to SG like nlpB-Tn5 inserted mutant. This mutant increases outer membrane permeability. It provides an explanation for SG susceptibility, because the antimicrobial peptide in SG would be able to translocate across the outer membrane more easily than in the wild type. These results indicate that nlpB and bla are likely to be important factors in terms of determining resistance against SG of Riptortus that is connected with the successful colonization of the Riptortus midgut.

We attempted to investigate antibacterial and proteolytic activities of bacteria isolated from three ethnic fermented seafoods in the east coast of South Korea, gajami sikhae, squid jeotgal, and fermented jinuari (Grateloupia filicina). Bacillus cereus ATCC 14579, Listeria monocytogenes ATCC 15313, Staphylococcus aureus KCTC 1916, Escherichia coli O157:H7 ATCC 43895, and Salmonella enterica serovar Typhimurium ATCC 4931 were selected to determine the antibacterial activity of the bacterial isolates. Among 233 isolates from the three foods, 36 isolates (15.5%) showed antibacterial activity against B. cereus ATCC 14579, the highest incidence of inhibition, followed by S. aureus KCTC 1916 (7.7%) and L. monocytogenes ATCC 15313 (6.0%). However, only five and three strains among the isolates exhibited inhibitory activity against Gram-negative indicators, E. coli ATCC 43895 and Sal. enterica ATCC 4931, respectively. The proteolytic activity of the isolates was determined via hydrolysis of skim milk after 24, 48, and 72 h incubation. After 72 h incubation, 72 out of 233 isolates (30.9%) showed proteolytic activity, and the isolates of fermented jinuari exhibited the highest incidence of proteolytic activity (60%, 36 isolates). These results suggest that ethnic fermented seafoods in the east coast of South Korea might be a promising source of bacterial strains producing antibacterial and proteolytic compounds.

사람과 어류에게 감염증을 유발하는 Edwardsiella sp., Streptococcus sp. 및 Vibrio sp. 의 해양 유해세균에 대한 해조류 추출물의 항균 활성을 조사하였다. 연구에 사용된 4종의 식용 해조류 중에서 감태 MeOH 추출물이 본 연구에서 사용 된 6종의 모든 해양 유해세균에 대해 넓은 범위의 항균 활성을 나타내었다. 감태의 MeOH 추출물의 유기용매 분획 추출물들 중에서, EtOAc 분획 추출물이 가장 높은 항균활성을 나타내었으며 6종의 해양 유해세균에 대하여 128 μg/mL에서 256 μg/mL의 MIC 값을 나타내었다. 또한, HPLC 분석에 의해 감태 EtOAc 분획 추출물에 phlorotannin 화합물인 dieckol이 다량 존재하고 있는 것이 확인 되었다. 결론적으로, 감태 추출물의 phlorotannin 화합물이 여러 유해세균에 대한 강한 항균활성을 나타내는 것처럼, 해양 유해세균에 대해서도 강한 항균활성을 나타내는 것으로 판단된다.

Recently, there is a growing interest of consumers in natural products thus a large number of natural preservatives have been studied as food additives. Among those natural preservatives, rosemary extract are commonly used by the food industry to extend the shelf life of several products. Nevertheless, the incorporation of the rosemary extract in food matrix is highly limited due to the low water solubility and poor chemical stability of constituents of rosemary extract. In this context, it is needed to find a way that can improve the water solubility to incorporate rosemary extract into aqueous system like foods. Hence, in this study we added surfactants that have a relatively high hydrophilic-liphophilic balance number into rosemary extract solution to increase the water solubility of rosemary extract and then investigated the microbial activities of rosemary extract with surfactants. Tween 20, decaglycerol monooleate, decaglycerol laurate and decaglycerol myristate were used in a range 0.1~4% and rosemary-surfactant solution was prepared by dissolving rosemary in surfactant added phosphate buffer (pH 7) as much as extract can be dissolved. Water solubility of rosemary-surfactant solution were examined by observance of the UV-vis spectra. The antimicrobial effects rosemary-surfactant solution on B.subtilis were also examined by paper disc diffusion method. Rosemary extract showed poor solubility in normal phosphate buffer but its water solubility was highly increased when surfactant was added. This tendency was lasted at all types of surfactant. This is because of amphipathic property of surfactant. Antimicrobial effect to B.subtilis was observed when a relatively lower concentration of surfactants were used, however, not in high concentrations. This result might be attributed to the formation of surfactant micelles containing rosemary extract when a relatively higher concentration of surfactants were used. The information presented may be useful for the development of a new rosemary-loaded delivery systems.

The discovery of various activities of natural plants has increased interest in halophytes. Suaeda australis and S. maritime are perennial halophytes that belong to the Chenopodiaceae family. Extracts of S. australis and S. maritime plants were investigated for concentration and time-dependent antibacterial and antioxidant activities using bacterial species and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, respectively, as well as total phenolic content. The S. australis extract (500 μg/mL) showed activity against all the bacterial species including P. aeruginosa, P. mirabilis, A. baumannii, and VRE with 61.1, 42.3, 44.49, and 40.38%, respectively, inhibition and suppressed of these four species for 12 h. Overall, the S. australis extract showed marked antibacterial activities while, in contrast, the S. maritime extract had excellent antioxidant effects. However, the effects of the two extracts were much lower than that of quercetin. The present study identified antibacterial activities of S. australis, and it would be necessary to perform further phytochemical studies of S. australis.