Pesticides in multigrains and risk assessment for Koreans by age group.

Using GC-MS/MS, 365 pesticides were analysed simultaneously in multigrains collected in the metropolitan area in 2018 and 2019. A risk assessment was performed for the detected pesticides. The limit of quantification, recovery and relative standard deviation for the pesticides ranged from 0.9-10.5 µg/kg, 70.3-89.3% and 3.0-10.3%, respectively. Among the 240 samples of multigrains, a total of 104 pesticides were detected, resulting in a detection rate of 32.9%. Out of these, 79 samples contained more than one pesticide. Risk assessment was conducted across all age groups, ranging from children to the elderly. The hazard quotient of phenothrin in glutinous rice was found to be 0.977, which was the highest in this study. However, the hazard index did not exceed 1 in any age group. These results indicated that the detected pesticides do not pose a serious public health concern. Nonetheless, regular monitoring is necessary to ascertain food safety.

Determination of 66 pesticide residues in livestock products using QuEChERS and GC-MS/MS.

Determinations of 66 pesticide residues in different matrices including beef, pork, chicken, eggs, and milk were conducted using GC-MS/MS combined with the quick easy cheap effective rugged safe (QuEChERS) method for sample extraction. A high linearity was achieved in the concentration range from 2.5 to 1000 µg/L (R 2 ≥ 0.99), and the limit of quantification for multi-class pesticides ranged from 0.74 to 23.1 µg/kg. The recovery ranged from 70.0 to 120%, while the reproducibility of the measurements was between 0.23 and 19.9%. Monitoring was conducted for livestock products purchased from local markets. Chlorpyrifos and fenitrothion in beef and chlorpyrifos in pork were detected below the maximum residue limits for the respective samples. No detectable residues were found in the other samples. Due to its high efficiency, reproducibility, and simple analytical operation, the proposed method can be applied to the regular monitoring of multi-residue pesticides in livestock products.

High-throughput simultaneous analysis of multiple pesticides in grain, fruit, and vegetables by GC-MS/MS.

A multi-component quantitative GC-MS/MS method for monitoring and inspecting agricultural products was developed for the simultaneous determination of 365 pesticide residues in grain, beans, fruit and vegetables. Twenty-six pesticides that have been authorised in foreign countries but not in Korea were included in the newly adapted Korean positive list system. The method was validated by analysing spiked samples at three concentrations (0.01, 0.05, and 0.1 mg/kg) for brown rice, soy beans, mandarin orange, potato and green pepper matrice, which represented grain, beans, fruit, and vegetables. More than 95% of 365 compounds satisfied the validation criteria of 70-120% recovery and ≤20% relative standard deviation obtained through the proposed simultaneous multi-component analysis. Twenty-two types of pesticides were detected in 76 food samples, whose concentrations were below the maximum residue limits. Among the newly added pesticides, lambda-cyhalothrin, an analogue of cyhalothrin, was detected in peaches. The method can be applied to the analysis and inspection of pesticide residues in domestic and imported agricultural products for safety control.

Mesonia phycicola sp. nov., isolated from seaweed, and emended description of the genus Mesonia.

An aerobic, Gram-reaction-negative, non-motile, catalase- and oxidase-positive bacterium, designated strain MDSW-25(T), was isolated from seaweed collected in the vicinity of Mara Island in Jeju province, Republic of Korea. Colonies were smooth, circular and convex with entire edges and yellow in colour. Growth occurred at 10-30 degrees C, at pH 6.1-9.1 and in the presence of 1-12 % (w/v) NaCl. The major fatty acids were iso-C(15 : 0) (25.6 %) and iso-C(15 : 1) G (11.3 %), and the major menaquinone was MK-6. The DNA G+C content was 30.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain MDSW-25( T) belonged to the genus Mesonia, family Flavobacteriaceae . Sequence similarity with Mesonia mobilis and Mesonia algae was 97.5 and 95.4 %, respectively, but DNA relatedness between strain MDSW-25(T) and M. mobilis KCTC 12708(T) was only 47 %. A battery of phenotypic data, phylogenetic inference and DNA-DNA hybridization analyses supports the conclusion that strain MDSW-25(T) (=KCTC 22373(T) =DSM 21425(T)) represents a novel species of the genus Mesonia , for which the name Mesonia phycicola sp. nov. is proposed. On the basis of new data obtained in this study, an emended description of the genus Mesonia is also proposed.

Ponticaulis koreensis gen. nov., sp. nov., a new member of the family Hyphomonadaceae isolated from seawater.

An obligately halophilic, stalked bacterium, designated strain GSW-23(T), was isolated from seawater that had been collected on the coast of Jeju, Korea. Cells of the strain were characteristically Gram-negative, aerobic, chemo-organotrophic, non-budding, motile rods or vibrioids that possessed prosthecae and holdfasts. Multiplication occurred by means of binary fission. The major ubiquinone was Q-10. The dominant cellular fatty acids were summed feature 7 (one or more of C(18 : 1)omega9c, C(18 : 1)omega12t and C(18 : 1)omega7c; 37.1 %), C(16 : 0) (25.5 %) and C(18 : 0) (14.1 %). The DNA G+C content was 53.3 mol%. 16S rRNA gene sequence analyses showed that the organism was related to members of the family Hyphomonadaceae and formed a distinct clade between members of the genus Hyphomonas and Hirschia baltica DSM 5838(T). Strain GSW-23(T) was most closely related to the genus Hyphomonas (92.5-93.9 % sequence similarity), but differed from members of the genus by reproduction by binary fission, some physiological properties (gelatin liquefaction and tolerance of 6 % NaCl) and chemotaxonomic features (major fatty acids, major quinones and DNA G+C content). The other genera of the family can be readily differentiated from the isolate by a battery of cultural, physiological and chemotaxonomic characteristics. On the basis of the phenotypic and phylogenetic data presented here, strain GSW-23(T) represents a novel genus and species in the family Hyphomonadaceae, for which the name Ponticaulis koreensis gen. nov., sp. nov. is proposed. The type strain of Ponticaulis koreensis is strain GSW-23(T) (=KCTC 22146(T) =DSM 19734(T) =JCM 14975(T)).

Hirschia maritima sp. nov., isolated from seawater.

A Gram-negative, aerobic, orange-coloured bacterium, designated strain GSW-2T, was isolated from seawater sampled at a beach and its taxonomic status was established by using a polyphasic approach. Vegetative cells produced a prostheca and reproduced by budding. Mature vegetative cells were spherical, oval- or rod-shaped (0.6-1.1x1.2-1.3 microm) and both vegetative cells and buds produced one or more flagella. Cells grew well at 30 degrees C and at pH 8.1-9.1, and produced a non-diffusible pigment. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GSW-2T was most closely related to the type strain of Hirschia baltica (97.5% similarity), a member of the family Hyphomonadaceae, class Alphaproteobacteria. Chemotaxonomic characteristics supported the assignment of strain GSW-2T to the genus Hirschia, including the dominant cellular fatty acids (summed feature 7 and C16:0), isoprenoid quinone (mainly Q-10) and DNA G+C content (44.5 mol%). Levels of DNA-DNA relatedness between strain GSW-2T and Hirschia baltica DSM 5838T were 8.8-13.6%. On the basis of phenotypic features and DNA-DNA hybridization data, strain GSW-2T is considered to represent a novel species of the genus Hirschia, for which the name Hirschia maritima sp. nov. is proposed. The type strain is GSW-2T (=DSM 19733T=JCM 14974T).

Nitratireductor kimnyeongensis sp. nov., isolated from seaweed.

An aerobic, Gram-negative, catalase-positive, oxidase-positive bacterium was isolated from a dried seaweed sample collected from Kimnyeong Beach in Jeju, Republic of Korea. The cells of the organism, designated strain KY 101(T), were rods (0.4-0.5x1.2-2.7 mum) and motile by means of flagella. The colonies of the cells were 0.5-1 mm in diameter, smooth, circular, convex and light yellow in colour. The isolate showed growth at 10-40 degrees C, pH 6.1-12.1 and in the presence of 7 % NaCl. The major fatty acid was summed feature C(18 : 1)omega7c/C(18 : 1)omega9c/C(18 : 1)omega12t and the DNA G+C content was 60.4 mol%. 16S rRNA gene sequence studies showed that the organism was phylogenetically related to the family Phyllobacteriaceae, with Nitratireductor aquibiodomus (99.1 % sequence similarity) as the closest neighbour. The level of DNA-DNA relatedness between strain KY 101(T) and N. aquibiodomus DSM 15645(T) was 18.4-23.2 % (duplicate measurements). The combination of phenotypic differences and DNA-DNA hybridization data supports the suggestion that the isolate represents a novel species of the genus Nitratireductor, for which the name Nitratireductor kimnyeongensis sp. nov. is proposed. The type strain is strain KY 101(T) (=KACC 11904(T)=JCM 14851(T)).

Utilization of monolinolein as a substrate for conjugated linoleic acid production by Bifidobacterium breve LMC 520 of human neonatal origin.

This study was designed to isolate bifidobacteria from human intestines that efficiently converts monolinolein, a monoglyceride form of linoleic acid, into conjugated linoleic acid (CLA), as well as to optimize culture conditions for improving CLA production during milk fermentation. Among 150 screened neonatal bifidobacteria, Bifidobacterium breve LMC 520 showed the highest CLA-producing ability and was tested with different types of fat substrates at various concentrations to determine the optimal conditions for CLA production. Monolinolein was tested as a substrate for CLA production. The incubation time optimized for CLA production was 24 h, and CLA production was proportionally increased with monolinolein concentration. The incubation of LMC 520 with commercial starter strains caused minimal reduction in CLA production. Our results demonstrate that the CLA-producing ability of B. breve LMC 520 could offer beneficial effects when utilized as a starter culture for the development of functional dairy products.

Synthesis of conjugated linoleic acid by human-derived Bifidobacterium breve LMC 017: utilization as a functional starter culture for milk fermentation.

This study was performed to discover bifidobacteria isolated from human intestines that optimally convert linoleic acid (LA) to conjugated linoleic acid (CLA) and to optimize the culture conditions of milk fermentation. One hundred and fifty neonatal bifidobacteria were screened for CLA-producing ability, and Bifidobacterium breve LMC 017 was selected as it showed about 90% conversion of free LA in MRS broth. The selected strain showed resistance at 0.5% LA in microaerophillic conditions. When monolinolein (LA 90%) was used as a substrate for CLA production, the conversion rate was lower compared to free LA, but the growth rate was unaffected during the milk fermentation. There was no significant difference in CLA production between aerobic and anaerobic conditions, and little decline in CLA was shown after the maximal CLA level had been reached. CLA production increased by 80% with 24 h of incubation in milk containing additional skim milk (5%), where the proteins may have facilitated the production of CLA by enhancing the interaction of substrate with the bacteria. CLA production did not decline after 9 h of fermentation and an additional 12 weeks of storage with other commercial starters. This demonstrates the possibility of using this strain as a costarter in the production of CLA-enriched yogurt.