• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.955-961
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• 2020

Lactic acid bacteria (LAB) have caused many microbiological incidents in the brewing industry, resulting in severe economic loss. Meanwhile, traditional culturing method for detecting LAB are time-consuming for brewers. The present review introduces LAB as spoilage microbes in daily life, with focus on LAB in the brewing industry, targeting at the spoilage mechanism of LAB in brewing industry including the special metabolisms, the exist of the viable but nonculturable (VBNC) state and the hop resistance. At the same time, this review compares the traditional and novel rapid detection methods for these microorganisms which may provide innovative control and detection strategies for preventing alcoholic beverage spoilage, such as improvement of microbiological quality control using advanced culture media or different isothermal amplification methods.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.5
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• pp.867-878
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• 1994

A general overview of the lipid peroxidation and its nutritional significance are presented ,with emphasis on the reaction mechaisms, peroxidized products, further interaction and nutritional/biological deterioration in a series of oxidative process. Overall mechanism with various factors and elements for initiation , propagation and termination of free radical reaction is reviewed and the primary /secondary products of peroxidized lipids are defined. Since these products are potentially reactive substances that can cause deterioration of proteins /amino acids and vitamins (carotene, tocopherols and ascorbic acid etc), mechanism and actual damages of their deterioration in some foods and biological models are outlined. Especially , chemical changes caused by interaction of peroxidized products (related hydroperoxides, radicals and malonaldehye etc) and protein are emphasized here. And also, the detailed mechanisms on radical scavenging of the these vitamins which are the most prominent natural antioxidants are presented . Additionally , the possible roles of peroxidicaed lipids and their secondary products in the process of aging an carcinogenesis are briefly discussed . However, it is important to not that more detailed and integrated studies on the reaction kinetics, energetics of peroxidation, their decomposed products , biochemical interaction potential damaging/aging / carcinogenic effects, protection from their oxidative spoilage and novel antioxidants in food and heterogeneous biological systems will be essential in order to assessing the implication of lipid peroxidation to human nutrition and health.

• Journal of the Korean Society of Food Culture
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• v.34 no.2
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• pp.201-207
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• 2019

This review summarizes the studies on a wide variety of yeast found in kimchi and the effects of yeast on kimchi fermentation, and discusses the direction for further research. Yeast belongs to the genera Trichosporon, Saccharomyces, Sporisorium, Pichia, Lodderomyces, Kluyveromyces, Candida, Debaryomyces, Geotrichum, Kazachstania, Brassica, Yarrowia, Hanseniaspora, Brettanomyces, Citeromyces, Rhodotorula, and Torulopsis have been identified using culture-dependent methods and metagenomics analysis. The application of yeast as a starter into kimchi has resulted in an extension of shelf life and improvement of sensory characteristics due to a decrease in the amount of lactic acid. On the other hand, some yeast cause kimchi spoilage, which typically appears as an off-odor, texture-softening, and white-colony or white-film formation on the surface of kimchi. In contrast to lactic acid bacteria, there are limited reports on yeast isolated from kimchi. In addition, it is unclear how yeast affects the fermentation of kimchi and the mechanism by which white colony forming yeast predominate in the later stage of kimchi fermentation. Therefore, more research will be needed to solve these issues.

• Food Science of Animal Resources
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• v.26 no.3
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• pp.402-409
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• 2006

Although microorganisms are, in fact, the most diverse and abundant type of organism on Earth, the ecological functions of microbial populations remains poorly understood. A variety of bacteria including marine Vibrios encounter numerous ecological challenges, such as UV light, predation, competition, and seasonal variations in seawater including pH, salinity, nutrient levels, temperature and so forth. In order to survive and proliferate under variable conditions, they have to develop elaborate means of communication to meet the challenges to which they are exposed. In bacteria, a range of biological functions have recently been found to be regulated by a population density-dependent cell-cell signaling mechanism known as quorum-sensing (QS). In other words, bacterial cells sense population density by monitoring the presence of self-produced extracellular autoinducers (AI). N-acylhomoserine lactone (AHL)-dependent quorum-sensing was first discovered in two luminescent marine bacteria, Vibrio fischeri and Vibrio harveyi. The LuxI/R system of V. fischeriis the paradigm of Gram-negative quorum-sensing systems. At high population density, the accumulated signalstrigger the expression of target genes and thereby initiate a new set of biological activities. Several QS systems have been identified so far. Among them, an AHL-dependent QS system has been found to control biofilm formation in several bacterial species, including Pseudomonas aeruginosa, Aeromonas hydrophila, Burkholderia cepacia, and Serratia liquefaciens. Bacterial biofilm is a structured community of bacterial cells enclosed in a self-produced polymeric matrix that adheres to an inert or living surface. Extracellular signal molecules have been implicated in biofilm formation. Agrobacterium tumefaciens strain NT1(traR, tra::lacZ749) and Chromobacterium violaceum strain CV026 are used as biosensors to detect AHL signals. Quorum sensing in lactic acid bacteria involves peptides that are directly sensed by membrane-located histidine kinases, after which the signal is transmitted to an intracellular regulator. In the nisin autoregulation process in Lactococcus lactis, the NisK protein acts as the sensor for nisin, and NisR protein as the response regulator activatingthe transcription of target genes. For control over growth and survival in bacterial communities, various strategies need to be developed by which receptors of the signal molecules are interfered with or the synthesis and release of the molecules is controlled. However, much is still unknown about the metabolic processes involved in such signal transduction and whether or not various foods and food ingredients may affect communication between spoilage or pathogenic bacteria. In five to ten years, we will be able to discover new signal molecules, some of which may have applications in food preservation to inhibit the growth of pathogens on foods.