Melanin Bleaching and Melanogenesis Inhibition Effects of Pediococcus acidilactici PMC48 Isolated from Korean Perilla Leaf Kimchi.

Overproduction and accumulation of melanin in the skin will darken the skin and cause skin disorders. So far, components that can inhibit tyrosinase, a melanin synthase of melanocytes, have been developed and used as ingredients of cosmetics or pharmaceutical products. However, most of existing substances can only inhibit the biosynthesis of melanin while melanin that is already synthesized and deposited is not directly decomposed. Thus, their effects in decreasing melanin concentration in the skin are weak. To overcome the limitation of existing therapeutic agents, we started to develop a substance that could directly biodegrade melanin. We screened traditional fermented food microorganisms for their abilities to direct biodegrade melanin. As a result, we found that a kimchi-derived Pediococcus acidilactici PMC48 had a direct melanin-degrading effect. This PMC48 strain is a new strain, different from P. acidilactici strains reported so far. It not only directly degrades melanin, but also has tyrosinase-inhibiting effect. It has a direct melanindecomposition effect. It exceeds existing melanin synthesis-inhibiting technology. It is expected to be of high value as a raw material for melanin degradation drugs and cosmetics.

Inactivation of Escherichia coli and Staphylococcus aureus on contaminated perilla leaves by Dielectric Barrier Discharge (DBD) plasma treatment.

This study focused on sterilization methods for the reduction of microorganisms on perilla leaves by cylinder type Dielectric Barrier Discharge (DBD) plasma with underwater bubbler treatment. S. aureus and E. coli in a suspension were reduced to less than 3.4 and 0.5 log CFU/ml after the plasma treatment for 3 min, respectively. On the perilla leaves, they were also reduced to 4.8 and 1.6 log CFU/ml after the plasma treatment, respectively. The S. aureus and E. coli bacterial cell wall was damaged by the plasma treatment evident by scanning electron microscopic analysis. The observed infrared bands of the FTIR spectra demonstrated changes in protein, lipid, polysaccharide, polyphosphate group and other carbohydrate functionalities of plasma treated bacteria and untreated bacterial cell membranes. The degradation of the constituent bonds of the bacterial cell membrane by RONS generated from plasma destroys the DNA, RNA, and proteins within the cell, and may eventually cause cell death. In this study, H2O2 (13.68 µM) and NO3 (138 µM), which are the main factors generated by plasma, proved to have a bactericidal effect by inducing lipid peroxidation of bacterial cell membranes. In conclusion, cylinder type DBD plasma with underwater bubbler can be used as an environmentally friendly food disinfection device in cleaning processes of the food industry.

Genetic Diversity and Antibiotic Resistance Patterns of Staphylococcus Aureus Isolated from Leaf Vegetables in Korea.

Staphylococcus aureus is an important foodborne pathogen on global basis. The current study investigated the genetic patterns in S. aureus isolates from leaf vegetables (n = 53). Additional isolates from livestock (n = 31) and humans (n = 27) were compared with the leaf vegetable isolates. Genes associated with toxins, antibiotic resistance, and pulsed-field gel electrophoresis (PFGE) patterns were analyzed. At least 1 enterotoxin-encoding gene (sea, seb, sec, sed, and see) was detected in 11 of 53 (20.75%) leaf vegetable isolates. When the agr (accessory gene regulator) grouping was analyzed, agr II was the major group, whereas agr IV was not present in leaf vegetable isolates. All S. aureus isolates from leaf vegetables were resistant to more than one of the antibiotics tested. Nineteen of 53 (35.85%) isolates from leaf vegetables exhibited multidrug-resistance, and 11 of these were MRSA (methicillin-resistant S. aureus). A dendrogram displaying the composite types of S. aureus isolates from 3 origins was generated based on the combination of the toxin genes, agr genes, antibiotic resistance, and PFGE patterns. The isolates could be clustered into 8 major composite types. The genetic patterns of S. aureus isolates from leaf vegetables and humans were similar, whereas those from livestock had unique patterns. This suggests some S. aureus isolates from leaf vegetables to be of human origin.

Dominant colonization and inheritance of Methylobacterium sp. strain OR01 on perilla plants.

Pink-pigmented facultative methylotrophs (PPFMs) are major inhabitants of the phyllosphere. In a preceding study, we found that perilla plants harbor a dominant population of PPFMs on their leaves and seeds, and that the closest relative of PPFMs (Methylobacterium sp. strain OR01 as representative strain) isolated from red perilla seeds was M. fujisawaense DSM5686(T). In the present study, the specific interaction between red perilla and Methylobacterium species was investigated. All the PPFMs isolated from red perilla seeds harvested in the Ohara area of Kyoto, Japan in 2009, 2010, and 2011 and the PPFMs isolated from red perilla leaves planted at four geographically different places in Japan had 16S rRNA sequences identical to that of strain OR01. Direct transmission of PPFMs from seeds to leaves and the competitiveness of strain OR01 were confirmed. This report is the first step toward understanding the species-level specificity of the interaction between perilla plants and Methylobacterium species.

Survival and growth of foodborne pathogens in minimally processed vegetables at 4 and 15 °C.

UNLABELLED: We conducted this study to investigate the survival and growth of pathogens on fresh vegetables stored at 4 and 15 °C. Vegetables (romaine lettuce, iceberg lettuce, perilla leaves, and sprouts) were inoculated with 4 pathogens (Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli O157:H7) and stored at 2 different temperatures for different periods of time (3, 6, 9, 12, and 15 d at 4 °C and 1, 2, 3, 5, and 7 d at 15 °C). Populations of the 4 pathogens tended to increase on all vegetables stored at 15 °C for 7 d. Populations of E. coli O157:H7 and S. Typhimurium increased significantly, by approximately 2 log10 CFU/g, on loose and head lettuce stored at 15 °C for 1 d. No significant differences were observed in the growth of different pathogens on vegetables stored at 4 °C for 15 d. E. coli O157:H7 did not survive on sprouts stored at 15 or 4 °C. The survival and growth of food pathogens on fresh vegetables were very different depending on the pathogen type and storage temperature. PRACTICAL APPLICATION: Survivals and growth of pathogens on various vegetables at 4 and 15 °C were observed in this study. Survivals and growth of pathogens on vegetables were different depending on the pathogen type and storage temperature. Therefore, vegetables should be stored under refrigerated conditions (below 4 °C) prior to consumption. This recommendation may vary depending on the type of vegetable.