• Journal of Microbiology and Biotechnology
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• v.29 no.4
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• pp.507-517
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• 2019

Rhodotorula is a group of pigment-producing yeasts well known for its intracellular biosynthesis of carotenoids such as ${\beta}-carotene$, ${\gamma}-carotene$, torulene and torularhodin. The great potential of carotenoids in applications in food and feed as well as in health products and cosmetics has generated a market value expected to reach over $2.0 billion by 2022. Due to growing public concern over food safety, the demand for natural carotenoids is rising, and this trend significantly encourages the use of microbial fermentation for natural carotenoid production. This review covers the biological properties of carotenoids and the most recent findings on the carotenoid biosynthetic pathway, as well as strategies for the metabolic engineering methods for the enhancement of carotenoid production by Rhodotorula. The practical approaches to improving carotenoid yields, which have been facilitated by advancements in strain work as well as the optimization of media and fermentation conditions, were summarized respectively.

• Journal of Microbiology and Biotechnology
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• v.29 no.5
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• pp.667-686
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• 2019

Streptomyces are attractive microbial cell factories that have industrial capability to produce a wide array of bioactive secondary metabolites. However, the genetic potential of the Streptomyces species has not been fully utilized because most of their secondary metabolite biosynthetic gene clusters (SM-BGCs) are silent under laboratory culture conditions. In an effort to activate SM-BGCs encoded in Streptomyces genomes, synthetic biology has emerged as a robust strategy to understand, design, and engineer the biosynthetic capability of Streptomyces secondary metabolites. In this regard, diverse synthetic biology tools have been developed for Streptomyces species with technical advances in DNA synthesis, sequencing, and editing. Here, we review recent progress in the development of synthetic biology tools for the production of novel secondary metabolites in Streptomyces, including genomic elements and genome engineering tools for Streptomyces, the heterologous gene expression strategy of designed biosynthetic gene clusters in the Streptomyces chassis strain, and future directions to expand diversity of novel secondary metabolites.

• International Journal of Clinical Preventive Dentistry
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• v.14 no.4
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• pp.216-221
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• 2018

Objective: In this study, we tried to investigate the antimicrobial activity of natural herbaceous plant-derived essential oils against oral disease-causing bacterial strains and establish the scientific evidences to apply them to the dentifrice, mouthwash, and other uses. Methods: We used the disk diffusion method with 23 types of 100% natural essential oils to verify the antimicrobial effect against Streptococcus mutans, Porphyromonas gingivalis, and Lactobacillus rhamnosus. After adhering to the surface of the plate culture medium, $20{\mu}l$ of the essential oil was prepared, and the diameter of the transparent ring was measured after incubation for 24 hours. All the experiments were repeated three times. Results: Among 23 types of oils, 13 were effective against all three strains: myrrh, ginger, basil, carrot seed, tea tree, patchouli, ylang ylang, cypress, lemongrass, cinnamon, peppermint, lavender, and eucalryptus. Seventeen oils were effective against S. mutans, and myrrh, basil, and carrot seed showed high antimicrobial activity. Eighteen oils were effective against P. gingivalis, and tea tree, carrot seed, and cinnamons showed high antimicrobial activity. Sixteen oils were effective against L. rhamnosus, and carrot seed and peppermint cinnamon showed high antimicrobial activity. Conclusion: Consequently, 13 essential oils showed the antimicrobial activity against three bacterial strains, which indicates these essential oils might be used as the effective materials to suppress the growth of oral-disease inducing microorganisms. Moreover, essential oils that have been analyzed activities in this study will be mixed up within the constant range and analyzed their antimicrobial effects to examine the synergistic activity among them.

• Biomedical Science Letters
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• v.26 no.4
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• pp.383-388
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• 2020

Ingestion of food contaminated with microorganism, if not always, could lead to severe health problem. Preservatives has been added to food to prevent food from being contaminated with microorganism. But, these have potential to threaten the health. Therefore, much effort has been taken to find the safe materials showing the anti-microbial activity. In this study, we investigated the anti-bacterial activity of Oenothera lamarckiana aerial part extract against eight bacteria strain. In paper disc assay, extract inhibited the growth of Staphylococcus aureus, Methicillin-resistant S. aureus, Bacillus cereus and Shigella dysenteriae at 200 μg/disc, but not against Escherichia coli, E. coli O157:H7, Salmonella Typhi and S. enteritidis. Minimum inhibitory concentration (MIC) against Staphylococcus aureus, Methicillin-resistant S. aureus, Bacillus cereus and Shigella dysenteriae is 250, 250, 500 and 500 μg/mL, respectively. Compared with reported MIC of other plant resources, O. lamarckiana aerial part extract showed the relatively high anti-bacterial activity. O. lamarckiana aerial part could be suitable for the preservative development. But, it still remains to be studied to evaluate safety and so on.

• Mass Spectrometry Letters
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• v.13 no.4
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• pp.106-114
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• 2022

A rapid and reliable approach to the identification of microorganisms is a critical requirement for large-scale culturomics analysis. MALDI-TOF MS is a suitable technique that can be a better alternative to conventional biochemical and gene sequencing methods as it is economical both in terms of cost and labor. In this review, the applications of MALDI-TOF MS for the comprehensive identification of microorganisms and bacterial strain typing for culturomics-based approaches for various environmental studies including bioremediation, plant sciences, agriculture and food microbiology have been widely explored. However, the restriction of this technique is attributed to insufficient coverage of the mass spectral database. To improve the applications of this technique for the identification of novel isolates, the spectral database should be updated with the peptide mass fingerprint (PMF) of type strains with not only microbes with clinical relevance but also from various environmental sources. Further, the development of enhanced sample processing methods and new algorithms for automation and de-replication of isolates will increase its application in microbial ecology studies.

• Journal of Korean Dental Science
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• v.16 no.1
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• pp.35-46
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• 2023

Purpose: Culture-based methods for microbiological diagnosis and antibiotic susceptibility tests have limitations in the management of orofacial infections. We aimed to profile pus microbiota and identify antibiotic resistance genes (ARGs) using a culture-independent approach. Materials and Methods: Genomic DNA samples extracted from the pus specimens of two patients with orofacial abscesses were subjected to shotgun sequencing on the NovaSeq system. Taxonomic profiling and prediction of ARGs were performed directly from the metagenomic raw reads. Result: Taxonomic profiling revealed obligate anaerobic polymicrobial communities associated with infections of odontogenic origins: the microbial community of Patient 1 consisted of one predominant species (Prevotella oris 74.6%) with 27 minor species, while the sample from Patient 2 contained 3 abundant species (Porphyromonas endodontalis 33.0%; P. oris 31.6%; and Prevotella koreensis 13.4%) with five minor species. A total of 150 and 136 putative ARGs were predicted in the metagenome of each pus sample. The coverage of most predicted ARGs was less than 10%, and only the CfxA2 gene identified in Patient 1 was covered 100%. ARG analysis of the seven assembled genome/metagenome datasets of P. oris revealed that strain C735 carried the CfxA2 gene. Conclusion: A metagenomics-based approach is useful to profile predominantly anaerobic polymicrobial communities but needs further verification for reliable ARG detection.

• Mycobiology
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• v.50 no.6
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• pp.408-419
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• 2022

Filamentous fungi that could be classified into Aspergillus flavus/oryzae were isolated from traditionally fermented meju commercially available in Korea. The samples were analyzed for aflatoxin B1 and ochratoxin A contamination by HPLC; however, no toxin was detected. In addition, fungal and bacterial metagenomic sequencing were performed to analyze the microbial distribution in the samples. The results revealed that the distribution and abundance of fungi and bacteria differed considerably depending on the production regions and fermentation conditions of the meju samples. Through morphological analysis, ITS region sequencing, and assessment of the aflatoxin-producing ability, a total of 32 A. flavus/oryzae strains were identified. PCR analysis of six regions with a high mutation frequency in the aflatoxin gene cluster (AGC) revealed a total of six types of AGC breaking point patterns. The A. flavus/oryzae strains did not exhibit the high amylase activity detected in the commercial yellow koji strain (starter mold). However, their peptidase and lipase activities were generally higher than that of the koji isolates. We verified the safety of the traditionally fermented meju samples by analyzing the AGC breaking point pattern and the enzyme activities of A. flavus/oryzae strains isolated from the samples. The isolated strains could possibly be used as starter molds for soybean fermentation.

• Journal of Microbiology and Biotechnology
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• v.33 no.4
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• pp.419-429
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• 2023

Ultraviolet C (UV-C, 200-280 nm) light has germicidal properties that inactivate a wide range of pathogenic and spoilage microorganisms. UV-C has been extensively studied as an alternative to thermal decontamination of fruit juices. Recent studies suggest that the efficacy of UV-C irradiation in reducing microorganisms in fruit juices is greatly dependent on the characteristics of the target microorganisms, juice matrices, and parameters of the UV-C treatment procedure, such as equipment and processing. Based on evidence from recent studies, this review describes how the characteristics of target microorganisms (e.g., type of microorganism/strain, acid adaptation, physiological states, single/composite inoculum, spore, etc.) and fruit juice matrices (e.g., UV absorbance, UV transmittance, turbidity, soluble solid content, pH, color, etc.) affect the efficacy of UV-C. We also discuss the influences on UV-C treatment efficacy of parameters, including UV-C light source, reactor conditions (e.g., continuous/batch, size, thickness, volume, diameter, outer case, configuration/arrangement), pumping/flow system conditions (e.g., sample flow rate and pattern, sample residence time, number of cycles), homogenization conditions (e.g., continuous flow/recirculation, stirring, mixing), and cleaning capability of the reactor. The collective facts indicate the immense potential of UV-C irradiation in the fruit juice industry. Existing drawbacks need to be addressed in future studies before the technique is applicable at the industrial scale.

• Animal Bioscience
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• v.36 no.9
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• pp.1426-1434
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• 2023

Objective: The objective of this study was to evaluate the effect of Debaryomyces hansenii isolated from dry-aged beef on the tenderness and flavor attributes of low-grade beef during dry aging. Methods: Five D. hansenii strains were isolated from dry-aged beef samples. The rump of low-grade beef was inoculated with individual D. hansenii isolates and subjected to dry aging for 4 weeks at 5℃ and 75% relative humidity. Microbial contamination levels, meat quality attributes, and flavor attributes in the dry-aged beef were measured. Results: Of the five isolates, the shear force of dry-aged beef inoculated with SMFM201812-3 and SMFM201905-5 was lower than that of control samples. Meanwhile, all five isolates increased the total free amino acid, glutamic acid, serine, glycine, alanine, and leucine contents in dry-aged beef. In particular, the total fatty acid, palmitic acid, and oleic acid contents in samples inoculated with D. hansenii SMFM201905-5 were higher than those in control samples. Conclusion: These results indicate that D. hansenii SMFM201905-5 might be used to improve the quality of beef during dry aging.

• Korean Journal of Food Science and Technology
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• v.40 no.4
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• pp.424-429
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• 2008

To investigate the acid tolerance characteristics of the acid-resistant mutant, Leuconostoc paramesenteroides P-200, as a kimchi starter, this study examine proton permeability, ATPase activity, glycolysis activity, $Mg^{2+}$ release, and membrane fatty acid composition, and compared the data to that of its wild-type, L. paramesenteroides LP-W. In the proton permeability experiment, the LP-W and P-200 strains' average maximum half-time $(t_{1/2})$ values for pH equilibration through the cell membrane were approximately 5.7 and 9.3 min in 150mM KCl solution, and 4.2 and 8.3 min in 3% NaCl solution, respectively. Their values and pH levels for maximal specific ATPase activity showed that P-200 had greater activity than LPW. And the results of pH-dependent glycolysis activity showed that P-200 had greater activity than LP-W. Furthermore, after 2 hr at pH 4.0, LP-W and P-200 had percent magnesium release values of approximately 12% and 34%, respectively. A comparison of their membrane fatty acid compositions indicated that C18 and cyclo-C19 were the major different fatty acids between the two strains, and their contents of C18 and cyclo-C19 were 2.5% and not detected, respectively, in LP-W, and 6.4% and 11.4%, respectively, in P-200. These results indicate that the P-200 strain has significantly improved acid tolerance as compared to its wild type, LP-W.