• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.5
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• pp.1069-1075
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• 1999

The sterilization was attempted to improve the quality deterioration of soybean paste during its storage. For this experiment, soybean paste was sterilized at 80oC for 30 minutes and stored during 6 months at 15oC and 30oC, respectively. The total approximate composition contents were moisture 52.5%, crude protein 11.94%, crude fat 2.0%, amino nitrogen 413.3mg%, sodium chloride 11.61% and ash 15.5%. According to the increase of storage period, pH was decreased gradually because of the increase of organic acids by the metabolism of microorganisms and the acid accumulation by acid forming bacteria, but titratable acidity was increased during storage. Amino nitrogen was rapidly increased for the first one or two month storage period and maintained as the same level for the rest of them. Each amino acid contents of soybean paste, which were glutamic acid, tryptophan, proline, arginine, and aspartic acid, had much higher level than others. In color changes sterilized soybean paste(SSP) was much lower than that of raw ones(RSP). Hunter L and b values on the surface of soybean paste were decreased during storage, and the decreasing levels were higher at 30oC than at 15oC. Hunter a value, however, was increased a little in the initial storage, and thereafter it was decreased. Lactic acid bacteria, yeasts, and molds were disappeared completely by the sterilization. However, the bacteria of aerobes and anaerobes were not disappeared by this processing.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.415-423
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• 2016

This study was carried out to obtain basic data for the industrial use of Weissella koreensis and Lactobacillus sakei. The antibacterial activity of supernatants obtained from W. koreensis and L. sakei were tested against pathogenic bacteria such as Escherichia coli KCCM 11234, Salmonella enteritidis KCCM 3313, Salmonella enteritidis KCCM 12021, Salmonella typhimurium KCCM 40253, and Salmonella typhimurium KCCM 15. The supernatant of L. sakei showed antibacterial activity against E. coli KCCM 11234, S. enteritidis KCCM 12021, and S. typhimurium KCCM 15, while the supernatant of W. koreensis showed antibacterial activity against E. coli KCCM 11234 and S. enteritidis KCCM 12021. The effect of pH changes and heat treatment on antibacterial activity of the supernatants was examined using the sensitive pathogenic bacteria (E. coli KCCM 11234, S. enteritidis KCCM 12021 and S. typhimurium KCCM 15). Antibacterial activity against sensitive pathogenic bacteria was maintained under heat treatment at all temperatures, but there was no antibacterial activity associated with pH modification. Furthermore, it was confirmed that the antibacterial activity of the supernatants obtained from W. koreensis and L. sakei was a result of organic acids including, lactic, acetic, phosphoric, succinic, pyroglutamic, citric, malic, and formic acids. Therefore, the present study showed that the organic acids produced by L. sakei and W. koreensis exhibited a strong antibacterial activity against pathogenic bacteria. Moreover, in the food industry, these organic acids have the potential to inhibit the growth of pathogenic bacteria and improve the quality of stored food.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.4 no.2
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• pp.86-94
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• 2023

Climate change is more rapid in the Arctic than elsewhere in the world, and increased precipitation and warming are expected cause changes in biogeochemical processes due to altered microbial communities and activities. It is crucial to investigate microbial responses to climate change to understand changes in carbon and nitrogen dynamics. We investigated the effects of increased temperature and precipitation on microbial biomass and community structure in dry tundra using two depths of soil samples (organic and mineral layers) under four treatments (control, warming, increased precipitation, and warming with increased precipitation) during the growing season (June-September) in Cambridge Bay, Canada (69°N, 105°W). A phospholipid fatty acid (PLFA) analysis method was applied to detect active microorganisms and distinguish major functional groups (e.g., fungi and bacteria) with different roles in organic matter decomposition. The soil layers featured different biomass and community structure; ratios of fungal/bacterial and gram-positive/-negative bacteria were higher in the mineral layer, possibly connected to low substrate quality. Increased temperature and precipitation had no effect in either layer, possibly due to the relatively short treatment period (seven years) or the ecosystem type. Mostly, sampling times did not affect PLFAs in the organic layer, but June mineral soil samples showed higher contents of total PLFAs and PLFA biomarkers for bacteria and fungi than those in other months. Despite the lack of response found in this investigation, long-term monitoring of these communities should be maintained because of the slow response times of vegetation and other parameters in high-Arctic ecosystems.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.2
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• pp.254-260
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• 1995

Yogurt base were prepared from milk added with skim milk powder or Aloe vera powder and femented with lactic acid bacteria(the single or mixed strain of Lactobacillus bulgaricus and Streptococcus thermophilus). The yogurt product were evaluated for acid production(pH, titratable acidity), number of viable cell, viscosity, sensory property and quality-keeping property. The composition of organic acid were also analyzed by HPLC. Addition of Aloe vera remarkably accelerated acid production, and titratable acidity of Aloe vera yogurts(1.293∼1.407%) after 24 hours incubation was higher than that of yogurts added with only skim milk powder(9.98∼1.110%). Yogurt fermented with the mixed strain of L. bulgaricus and Sc. thermophilus was more acidic than that of single strains. The propagation of lactic acid bacteria was stimulated by Aloe vera and the number of viable cell after 24 hours incubation were above 9.87log CFU/ml. Viscosity of Aloe vera yogurt(3,860∼4,300CPS) was higher than that of yogurt with only skim milk powder(2,402∼2,604CPS). The overall sensory score of Aloe vera yogurt femented by mixed strain was the best of tested yogurt. When yogurt with Aloe vera was kept at 5℃ for 15 day, it's quality-keeping property was relatively good. The major organic acid of Aloe vera yogurt was lactic acid and lactic acid content of yogurt increased by addition of Aloe vera powder. The citric acid content decreased wtih fermentation and malonic acid, pyroglutaric acid and α-ketoglutaric acid were analyzed out a little.

• Journal of Dairy Science and Biotechnology
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• v.41 no.3
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• pp.126-137
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• 2023

In this study, we isolated lactic acid bacteria from Allium wakegi and examined the usability of culture supernatants obtained from these lactic acid bacteria. The antibacterial activity of the culture supernatant obtained from the isolated lactic acid bacteria against the pathogens Escherichia and Salmonella spp. was measured. The obtained lactic acid bacteria culture medium showed significant antibacterial activity against pathogenic bacteria in a dose-dependent manner. The effects of pH and heat denaturation on the observed anti-pathogenic bacterial activity was also investigated. Adjusting the culture supernatant to pH 7 resulted in loss of all antibacterial activity against pathogenic bacteria, suggesting that the antibacterial activity of the obtained culture supernatant against pathogenic bacteria is influenced by organic acids. Assessment of the heat stability of the anti-pathogenic bacterial activity revealed that heat treatment did not diminish activity. The obtained lactic acid bacteria culture medium is thus stable against heat.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.3
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• pp.75-82
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• 2008

Two UASB reactors were operated to investigate the effect of high concentration of sulfate on anaerobic digestion of propionate using an upflow anaerobic sludge blanket (UASB) reactor. An organic loading rate of $1.2kg\;COD/m^3{\cdot}d$ and a hydraulic retention time of 1.6 d were maintained during this study. In the absence of sulfate, the UASB reactor achieved about 95% removal of chemical oxygen demand whereas in the presence of $2,000\;SO_4^{2-}mg/L$, the COD removal rate decreased to 83% due probably to the inhibition of dissolved sulfide inhibition. Interactions between the methane producing bacteria (MPB) and sulfate reducing bacteria (SRB) were measured to investigate the competition between MPB and SRB. The MPB consumed average 58% of the available electron donors at $COD/SO_4^{2-}$ ratio of 1. Propionate was consumed mainly by SRB, converting sulfate into sulfide and suppressing the methane production. The specific methanogenic activity (SMA) using acetate and propionate increased as microorganism acclimated to the substrate.

• Ocean and Polar Research
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• v.36 no.1
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• pp.25-37
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• 2014

To understand the degradation processes of organic matter related to sulfate reduction by Sulfate Reduction Bacteria (SRB) in the tidal flat sediments of Hwang-do and Sogeun-ri, Tae-an Peninsula in Chungnam-do, biogeochemical characteristics were analyzed and highlighted using specific microbial biomarkers. The organic geochemical parameters (TOC, ${\delta}^{13}C_{org}$, C/N ratio, long-chain-n-alkane) indicate that most of the organic matter has been derived from marine phytoplankton and bacteria in the fine-grained sediment of Sogeun-ri, although terrestrial plant components have occasionally been incorporated to a significant degree in the coarse-grained sediment of Hwang-do. The concentration of sulfate in pore water is a constant tendency with regard to depth profile, while methane concentration appears to be slightly different with regard to depth profile at the two sites. Especially, the sum of bacteria fatty acid (a-C15:0 + i-C15:0 + C16:1w5) confirms that the these concentrations in Sogeun-ri are related to the degradation of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) compounds from the crude oil retained in the sediments as a result of the Hebei Spirit oil-spill accident in 2007. The methane-related microbial communities as shown by lipid biomarkers (crocetane, PMI) are larger in some sedimentary sections of Hwang-do than in the Sogeunri tidal flat. These findings suggest that methane production by microbiological processes is clearly governed by SRB activity along the vertical succession in organic-enriched tidal flats.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.150-155
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• 1997

The twenty strains of Lactobacillus genus were tested for the optimal sponge fermentation of soda cracker. The six strains such as L. brevis, L. delbrueckii, L. fermentum, L. leichmanii, L. plantarum and L. sanfrancisco were selected because these strains did not smell off-flavor and showed the high value of TTA (total titrable acidity) after the fermentation. The selected strains consisted of the five strains of L. brevis, L. delbrueckii, L. fermentum, L. leichmanii and L. plantarum that mainly inhabited soda clacker and L. sanfrancisco that existed in San Francisco bread. The lactic acid bacteria were inoculated to the medium containing 10% wheat flour and then pH, TTA, acetic acid and lactic acid were measured during the sponge fermentation. The four strains of L. brevis, L. delbrueckii, L. fermentum and L. plantarum were used for the mixed lactic acid bacteria of sponge fermentation because the TTAs of L. brevis, L. fermentum and L. plantarum were higher than those of other lactic acid bacteria and L. delbrueckii rapidly produced organic acids and a large amount of acetic acid. Among the combination of L. brevis, L. fermentum, L. delbrueckii and L. plantarum, the mixed lactic acid bacteria of L. brevis, L. fermentum and L. plantarum showed the highest TTA, the lowest pH and the largest amount of acetic acid. Therefore, the mixed lactic acid bacteria of L. brevis, L. fermentum and L. plantarum were used for optimal sponge fermentation of soda cracker.

• Journal of Food Hygiene and Safety
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• v.35 no.5
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• pp.419-429
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• 2020

The problems caused by foodborne pathogens are not only a concern to the food industry but also with regard to global public health. Over the years, fermentation technology has proved to be one of the cheapest and safest methods for inactivating and controlling pathogenic microorganisms in food. Scientific evidence shows that lactic acid bacteria fermentation exerts significant antimicrobial effect against pathogenic bacteria and viruses. Lactic acid bacteria metabolites such as organic acids, bacteriocins and hydrogen peroxides have adverse effects on foodborne pathogens which lead to their inhibition. These compounds do not only cause physical injuries, but also have significant effects on the pathogens' gene expression. Furthermore, the presence of lactic acid bacteria in food provides nutritional competition among foodborne pathogens, and all these factors together suppress their growth. This study reviews our current knowledge of the antimicrobial abilities of lactic acid bacteria, their molecular mechanisms, and their application for inactivating foodborne pathogens.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.323-327
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• 1990

The synthesis and some biological properties of $7{\beta} $-[2-(Z)-(2-aminothiazole-4-yl)-2-(N-substitutedcar bonyl)ethoxyiminoacetamido]-3-vinyl-3-cephem-4- carboxylic acid are described. The effect of substituents on the carbamoly group in the 7-side chain were investigated in order to improve antibacterial activities. Two of these new orally active $7{\beta} $-lactam derivatives showed wide expanded antimicrobial activities against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa, as well as good stability to $7{\beta} $ -lactamases.