• Journal of Microbiology and Biotechnology
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• v.29 no.6
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• pp.933-943
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• 2019

Gamma-aminobutyric acid (GABA)-producing strains were isolated from four edible insects and subjected to 16S rRNA sequence analysis. Among the four GABA-producing bacteria, Enterococcus avium JS-N6B4 exhibited the highest GABA-production, while cultivation temperature, initial pH, aerobic condition, and mono-sodium glutamate (MSG) feeding were found to be the key factors affecting GABA production rate. The culture condition was optimized in terms of glucose, yeast extract, and MSG concentrations using response surface methodology (RSM). GABA production up to 16.64 g/l was obtained under the conditions of 7 g/l glucose, 45 g/l yeast extract, and 62 g/l MSG through the optimization of medium composition by RSM. Experimental GABA production was 13.68 g/l, which was close to the predicted value (16.64 g/l) calculated from the analysis of variance, and 2.79-fold higher than the production achieved with basic medium. Therefore, GABA-producing strains may help improve the GABA production in edible insects, and provide a new approach to the use of edible insects as effective food biomaterials.

• Food Science of Animal Resources
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• v.42 no.6
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• pp.928-941
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• 2022

This study aimed to analyze the microbiological composition and sensory characterization of fermented sausage using strains isolated from Kimchi (GK1, Pediococcus pentosaceus SMFM2016-GK1; NK3, P. pentosaceus SMFM2016-NK3), Doenjang (D1, Debaryomyces hansenii SMFM2021-D1), and spontaneously fermented sausage (S8, D. hansenii SMFM2021-S8; S6, Penicillium nalgiovense SMFM2021-S6). The control was commercial starter culture. Nine treatments were applied [GD (GK1+D1), GS (GK1+S8), GDS (GK1+D1+S8), ND (NK3+D1), NS (NK3+S8), NDS (NK3+D1+S8), GND (GK1+NK3+D1), GNS (GK1+NK3+S8), and GNDS (GK1+NK3+D1+S8)] by mixing lactic acid bacteria and yeast, and S6 was sprayed. The microbial composition of fermented sausage was analyzed [aerobic bacteria (AC), Lactobacillus spp. (LABC), Staphylococcus spp. (STPC), and yeast and mold (YMC)], and pH and electronic nose and tongue measurements were taken. The AC, LABC, STPC, and YMC values of the control and treatment groups tended to increase during fermentation (p>0.05). The STPC values of the GD, GS, ND, and GDS groups were similar to that of the control on day 3. The pH of the control on day 3 was significantly lower than that of the GD, ND, and GND groups (p<0.05). Higher levels of 4-methylpentanol, 2-furanmethanol, and propyl nonanoate, which provide a "fermented" flavor, were detected in the GD group compared to in the control and other treatment groups. GD and ND groups showed higher umami values than the control and other treatment groups. Therefore, it is expected that GD can be valuable as a starter culture unique to Korea when manufacturing fermented sausage.

• Journal of Food Hygiene and Safety
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• v.26 no.2
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• pp.182-185
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• 2011

This study was conducted to develop an appropriated management for safety of children snacks sold around school. Total 598 items as targeted food were collected; 66 biscuits, 320 candies, 57 chocolates, 40 ice creams and 115 beverages. Microbiological hazards such as total aerobic bacteria, Coliforms, Escherichia coli, Bacillus ceruse, Yeasts & molds were measured by analytical method in Korean food code. Total aerobic bacteria and Yeasts & molds were detected in cookies at the level of less than 2.69 and 2.65 $log_{10}$ CFU/g and the detection rates were 54.55 and 62.12%, respectively. Bacillus cereus was detected in 1 snack only at the level of 1.39 $log_{10}$ CFU/g but it was less than Korean microbial standards and specifications (3 $log_{10}$ CFU/g). Total aerobic bacteria and Yeasts & molds were detected in candies less than 2.86, 3.36 $log_{10}$ CFU/g and the detection rates were 46,8% respectively. Total aerobic bacteria, Yeast & mold were detected in chocolates at the levels less than 2.52 and 1.87 $log_{10}$ CFU/g and the detection rates were 33 and 22% respectively. Total aerobic bacteria in both ice creams and beverages were detected at the levels less than 3.39 and 1.35 $log_{10}$ CFU/g and the detection rates were 82 and 5% respectively. Coliforms were found in one ice cream (1.39 $log_{10}$ CFU/g) only. The result of this study indicated that all children snacks around school were suitable for microbial standard and specifications in Korean Food Code. However, since most children snacks around school are circulated without proper storage temperature and handing condition, consistent microbial management for children snacks are needed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.2
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• pp.239-246
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• 2016

This study was performed to investigate changes in characteristics of Umbilicaria esculenta Yakju added with 0.5% and 1% grapefruit seed extracts (GSE) during storage for 75 days at $25^{\circ}C$ and 165 days at $4^{\circ}C$. Quality characteristics of pH, titratable acidity, turbidity, total aerobic microbes, and ethanol, glucose, acetic acid, and lactic acid contents were analyzed. Control group showed sharply increased pH, titratable acidity, turbidity, and acetic acid and lactic acid has contents while the 0.5% and 1% GSE groups added to Yakju did not show significant changes in pattern (P<0.05). Total aerobic microbes increased rapidly during storage from 15 days in the control group, and the 0.5% and 1% GSE groups showed gradually increased total aerobic microbes from 30 days of storage compared to the control group (P<0.05). In addition, in all test groups, coli, yeast, and fungus were not detected. Ethanol content slightly increased during storage and glucose content slightly decreased, but there were no large changes during storage between the control group and GSE groups. Therefore, 3 months and $4^{\circ}C$ are considered safe for 6 months of storage, and GSE is effective to improve shelf-life and quality improvement of Yakju.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.1
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• pp.100-110
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• 2020

Objective: The objective of this study was to isolate proteolytic microorganisms and evaluate their effects on proteolysis in total mixed ration (TMR) silages of soybean curd residue. Methods: TMRs were formulated with soybean curd residue, alfalfa or Leymus chinensis hay, corn meal, soybean meal, a vitamin-mineral supplement, and salt in a ratio of 25.0: 40.0:30.0:4.0:0.5:0.5, respectively, on a basis of dry matter. The microbial proteinases during ensiling were characterized, the dominate strains associated with proteolysis were identified, and their enzymatic characterization were evaluated in alfalfa (A-TMR) and Leymus chinensis (L-TMR) TMR silages containing soybean curd residue. Results: Both A-TMR and L-TMR silages were well preserved, with low pH and high lactic acid concentrations. The aerobic bacteria and yeast counts in both TMR silages decreased to about 10⁵ cfu/g fresh matter (FM) and below the detection limit, respectively. The lactic acid bacteria count increased to 10⁹ cfu/g FM. The total microbial proteinases activities reached their maximums during the early ensiling stage and then reduced in both TMR silages with fermentation prolonged. Metalloproteinase was the main proteinase when the total proteinases activities reached their maximums, and when ensiling terminated, metallo and serine proteinases played equally important parts in proteolysis in both TMR silages. Strains in the genera Curtobacterium and Paenibacillus were identified as the most dominant proteolytic bacteria in A-TMR and L-TMR, respectively, and both their proteinases were mainly with metalloproteinase characteristics. In the latter ensiling phase, Enterococcus faecium strains became the major sources of proteolytic enzymes in both TMR silages. Their proteinases were mainly of metallo and serine proteinases classes in this experiment. Conclusion: Proteolytic aerobic bacteria were substituted by proteolytic lactic acid bacteria during ensiling, and the microbial serine and metallo proteinases in these strains played leading roles in proteolysis in TMR silages.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.2
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• pp.218-221
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• 2002

Whole forage sorghum (saccharatum) cultivar FS5 was harvested at the soft dough ($303{\pm}9g\;kg^{-1}$ DM) stage of maturity. The sorghum was chopped into approximately 20 mm pieces and ensiled under laboratory conditions in 1.5 L Weck glass jars. At ensiling, it was treated with two commercial silage inoculants: Pioneer 1188 (Inoculant A) and Eco-corn (Inoculant B). The inoculant A and B was applied at ca $2{\times}10^5$ or $2{\times}10^4$ colony forming units $g^{-1}$ DM., respectively. Silage with no additives served as a control. Three jars per treatment were opened on days 2, 4, 8, 15 and 60 post-ensiling to study fermentation dynamics. After 60 days of ensiling the silages were analyzed and subjected to an aerobic stability test lasting 5 days. Results showed that both inoculants caused a more rapid rate of pH decrease and a higher amount of lactic acid production. All the silages were well preserved and were stable upon exposure to air. Inoculants did not influence (p>0.05) the ash and total N contents, but tended to reduce acetic acid (p<0.05), butyric acid (p<0.01) and propionic acid (p<0.01) contents, and to increase the lactic acid content (p<0.01). The lower DM content of silages treated with Inoculant A agrees with the greater gas loss resulting from the DM loss, which was in good agreement with the higher yeast counts upon aerobic exposure. Silage treated with inoculant B had the highest DM (p<0.05) and lactic acid contents (p<0.01), and the lowest acetic acid content (p<0.05), which agrees with the rapid reduction of pH and smaller gas loss. Inoculant B reduced the ADF (p<0.01), ADL and NDF (p<0.05) contents, which also indicates smaller losses of organic soluble material. The control silages contained the highest levels of volatile fatty acids but no lactic acid, indicating secondary fermentation. It was concluded that both inoculants may improve the fermentation process, since silages from all treatments were stable upon aerobic exposure, noadvantage could be attributed to any of the inoculants used.

• Applied Biological Chemistry
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• v.13 no.1
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• pp.43-50
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• 1970

To study the productivity of single cell protein from the petroleum hydrocarbon utilizing yeasts, 242 soil samples, such as oil soaked soil of gas stations and garage, coal, farm soil, and sewage, from 135 places in Korea were collected. From these samples 468 yeast strains which utilize petroleum hydrocarbon as a sole organic carbon source were isolated and identified by observing the growth rates. For the identified strains optimum culture conditions were determined and analysis of cell components were performed. 1. 90.8% of petroleum hydrocarbon utilizing yeast strains were found from oil soaked soil and about 10% from coal, farm soil and sewage etc. 2. The yeast strain of the highest cell productivity was isolated from oil soaked soil and was identified as Candida curvata HY-69-19. 3. The optimum culture conditions for the selected yeast strain were found to be pH 5.0, $28^{\circ}C$ and affluent aerated state. 4. Candida curvata HY-69-19 was found to utilize favorably the heavy gas oil fractionated at above $268.9^{\circ}C$ as carbon source and urea as inorganic nitrogen source. 5. The growth curve of this strain on heavy gas oil medium showed that the yeast has a lag phase up to 18 hours and logarithmic growth phase between 24 to 42 hours. Generation time was found to be between 3.8 and 4.5 hours during the logarithmic growth phase. 6. About 300 mg dried cells per heavy gas oil was harvested under the culture conditions of adjusted pH to 5.0 at time intervals of 6 hours for 54 hours and heavy gas oil urea for shaking culture medium. 7. Chemical composition of the yeast cell was found to be 40.25%, 14.81%, 24.32% and 10.63% for crude protein, crude lipid, carbohydrate and ashes, respectively.

• Journal of Applied Biological Chemistry
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• v.58 no.1
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• pp.61-64
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• 2015

As an edible coating, carnauba shellac wax (CSW) and lemongrass oil (LO) solution was prepared to extend the shelf life of 'Hongro' apples. During storage, there were significant differences in the populations of total aerobic bacteria, yeast, and molds between the coated apples and the control samples. The weight loss and vitamin C loss of apples coated with the CSW-LO solution were lower than those of the control. These results suggest that CSW-LO coating can be an effective method for improving quality of 'Hongro' apples.

• Food Science and Biotechnology
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• v.18 no.4
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• pp.1035-1037
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• 2009

In this study we analyzed the dynamic changes in microbiota composition during kochujang fermentation at $30^{\circ}C$. During fermentation, the viable cell counts slowly increased and reached $3.2{\times}10^7$ for aerobic bacteria, $8.3{\times}10^3$ for yeast, and $1.4{\times}10^3$ CFU/mL for fungi after 60 days. Bacilli were found to be the most dominant microorganisms throughout the fermentation process. Using the culture dependent method Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloquefaciens were found to be the main species during the early stages of fermentation; however, Bacillus pumilus and Bacillus stearothermophilus became the most dominant species during the late stage of fermentation. In contrast, when the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method was used Bacillus ehimensis was found to be the dominant species during the early stage of fermentation and Bacillus megaterium, B. pumilus, B. subtilis, and B. licheniformis were dominant in the ate stages. These results indicate various other Bacillus species rather than just B. subtilis and B. licheniformis might be involved in the fermentation of kochujang.

• Microbiology and Biotechnology Letters
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• v.22 no.4
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• pp.333-339
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• 1994

In order to screen microorganisms producing phospholipase D (PLD) [EC 3.1.4.4], culture broths of about 900 strains of soil bacteria were subjected to examine for the PLD activity. When the hydrolytic activity of PLD (H-activity) in the supernatant was determined, 64 strains produced PLD more than 0.3 unit/ml and all of them were actinomycetes. Among 26 culture broths tested, 6 ones had transphosphatidylation activity (T-activity) of 30~68%. When the strains except one were cultivated on 3 different media at 30$\circ$C for 3 days under aerobic condition, strain # 1090 on medium B (yeast extract 1%, peptone 1%, glucose 1.5%, glycerol 1%, CaCO$_{3}$ 0.4%, and pH 7.2) produced PLD with much higher H- and T-activity, which were 8.3 units/ml and 76.3%, respectively. Subsequently, time course of PLD production of the strain # 1090 during cultivation with aeration of 1 v/v/m and agitation of 400 rpm at 30$\circ$C for 5 days on medium B in jar fermentor was investigated. H-activty of PLD reached almost maximum (about 9 units/ml) after 32 hours and maximal T-activity was found to be about 80%.