Cell Counts Of Bacteria Research Articles

Effects of deleting peptidoglycan hydrolase genes on the viable cell counts of Bacillus amyloliquefaciens and the yield of alkaline protease

In order to explore the effect of peptidoglycan hydrolase on the viable cell counts of Bacillus amyloliquefaciens and the yield of alkaline protease, five peptidoglycan hydrolase genes (lytC, lytD, lytE, lytF and lytG) of B. amyloliquefaciens TCCC111018 were knocked out individually. The viable cell counts of the bacteria and their alkaline protease activities before and after gene deletion were determined. The viable cell counts of the knockout mutants BA ΔlytC and BA ΔlytE achieved 1.67×106 CFU/mL and 1.44×106 CFU/mL respectively after cultivation for 60 h, which were 32.5% and 14.3% higher than that of the control strain BA Δupp. Their alkaline protease activities reached 20 264 U/mL and 17 265 U/mL, respectively, which were 43.1% and 27.3% higher than that of the control strain. The results showed that deleting some of the peptidoglycan hydrolase genes effectively maintained the viable cell counts of bacteria and increased the activity of extracellular enzymes, which may provide a new idea for optimization of the microbial host for production of industrial enzymes.

Antioxidant Activities and Profile of Amino Acid of Yoghurt from Beef Milk Fermentation with Dadih Starter

Dadih is naturally fermented buffalo milk in bamboo tubes and known to have antioxidant, antibacterial, and antihypertensive activity. Lactic acid bacteria in dadih can use as a starter to produce yogurt. The study aimed to produce yogurt of cow's milk with dadih as a starter, to determine the antioxidant activity and amino acid composition. Dadih is added with concentration variation of 2.5; 5; 7.5 and 10% (v/v) and it fermented for 48 hours at room temperature. Lactic acid bacteria cell counts of dadih were calculated by the total plate count method. Yogurt was tested by organoleptics with 33 panelists and proximate analysis water, ash, fat and protein contens based on the Association of Official Analytical Chemist (AOAC) in 2005. Antioxidant activities of yogurt were tested by DPPH method (1,1-diphenyl-2-picrylhydrazyl). Amino acid composition of yogurt was analyzed using ultra performance liquid chromatography (UPLC). The research result of amount of LAB on dadih are 1.01 x 1011 CFU/mL, has fulfilled the requirements of SNI 2981: 2009. Yogurt produced with the addition of dadih by 10% (v/v) is most accepted by panelists. The highest antioxidant activity was obtained by yogurt with 2.5% addition of dadih with IC50 value of 78.28 ppm. Yogurt almost contain all essential and non-essensial amino acids including tyrosine and phenylalanine as the antioxidants. Measurement of water, ash, protein and fat content in the sample meets the requirements of SNI 2981: 2009.

Antioxidant Activities and Profile of Amino Acid of Yoghurt from Beef Milk Fermentation with Dadih Starter

Dadih is naturally fermented buffalo milk in bamboo tubes and known to have antioxidant, antibacterial, and antihypertensive activity. Lactic acid bacteria in dadih can use as a starter to produce yogurt. The study aimed to produce yogurt of cow's milk with dadih as a starter, to determine the antioxidant activity and amino acid composition. Dadih is added with concentration variation of 2.5; 5; 7.5 and 10% (v/v) and it fermented for 48 hours at room temperature. Lactic acid bacteria cell counts of dadih were calculated by the total plate count method. Yogurt was tested by organoleptics with 33 panelists and proximate analysis water, ash, fat and protein contens based on the Association of Official Analytical Chemist (AOAC) in 2005. Antioxidant activities of yogurt were tested by DPPH method (1,1-diphenyl-2-picrylhydrazyl). Amino acid composition of yogurt was analyzed using ultra performance liquid chromatography (UPLC). The research result of amount of LAB on dadih are 1.01 x 1011 CFU/mL, has fulfilled the requirements of SNI 2981: 2009. Yogurt produced with the addition of dadih by 10% (v/v) is most accepted by panelists. The highest antioxidant activity was obtained by yogurt with 2.5% addition of dadih with IC50 value of 78.28 ppm. Yogurt almost contain all essential and non-essensial amino acids including tyrosine and phenylalanine as the antioxidants. Measurement of water, ash, protein and fat content in the sample meets the requirements of SNI 2981: 2009.

Evaluation of Different Carrier Substances for the Development of an Effective Pelleted Biofertilizer for Rice (Oryza sativa L.) Using Co-inoculated Bacteria and Arbuscular Mycorrhizal Fungi

Aims: This study was aimed to compare aquatic weed, biochar and compost carrier substances for the development of effective pelleted biofertilizer for paddy (Oryza sativa L.) using co-inoculated bacteria, Azospirillum sp., Pseudomonas fluorescens and arbuscular mycorrhizal fungi (AMF).
 Place and Duration of Study: Faculty of Applied Sciences, Rajarata University of Sri Lanka, Mihintale, Sri Lanka between November 2018 and May 2019.
 Methodology: Pre-sterilized, 1 kg weight of ground carrier material was inoculated with 50 g of AMF propagules and 20 ml of 1.5 x 108 (CFU/ml) of each bacterial inoculant. Different types of pelleted biofertilizers were prepared as; aquatic weed and bioinoculum (P1), aquatic weed, bioinoculum and nutrient supplement mixture (P2), biochar and bioinoculum (P3), biochar, bioinoculum and nutrient supplement mixture (P4), compost and bioinoculum (P5), compost, bioinoculum and nutrient supplement mixture (P6). Rock phosphate and potassium feldspar was used as nutrient supplement mixture in developing some pelleted biofertilizers. Biofertilizer pellets were tested for the microbial survivability with the time by determining viable cell count of bacteria at two storage temperatures of 0°C and 30°C.
 Pot experiment was carried out to investigate the effects of prepared pelleted biofertilizers on growth and yield of rice and on some soil chemical and biological characteristics. Control (without biofertilizers) and above pelleted biofertilizers were added to the 3000 g of soil in pot with one paddy plant of variety BG 360. The treatments were arranged in a randomized complete block design (RCBD) with five replicates. Rice roots were screened for AMF colonization after harvesting.
 Results: According to Tukey’s Pairwise Comparison test, control and different treatments in pot experiment were significantly different for shoot height, number of seeds per panicle, 100 seeds weight and soil pH (p ≤ 0.05). However, there was no significant difference observed for bacterial count in prepared biofertilizers and biofertilizer applied soil, relative growth rate, plant dry and fresh weights and electrical conductivity. Among different pelleted biofertilizers, application of pellets consisted of compost with bioinoculant (P5), exceedingly enhanced the rice growth and yield. Compost, bioinoculum and nutrient supplement mixture (P6) added pellets were shown highest bacterial survivability at 30°C for seven days. Although AMF colonization of rice plants were low this was the first report of citing the presence of AMF in rice roots in Sri Lanka.
 Conclusion: These pelleted biofertilizers have the potential to be used for improved productivity of rice variety Bg 360. Therefore, developing such bioinoculants as biofertilizers and their efficient use could be considered as a sustainable solution for rice cultivation in Sri Lanka and worldwide.

Degradation of 4-tert-butylphenol in contaminated soil using Penicillium sp. CHY-2 isolated from pristine Antarctica

The feasibility of Penicillium sp. CHY-2 isolated from pristine Antarctic soil was evaluated for the remediation of 4-tert-butylphenol (4-t-BP) contaminated soil. The strain CHY-2 completely degraded 4-t-BP present in the artificially contaminated soil within three weeks. Also, the number of indigenous bacteria and fungi present in the soil were analyzed at different time intervals using colony forming unit (CFU) analysis. The viable cell count of fungi were increased from day 10 to day 21 in the contaminated soil, and it was in accordance with the decrement of 4-t-BP concentration. The viable cell count of bacteria also increased with respect to time. The results suggested that the strain CHY-2 can be applied for the treatment of 4-t-BP contaminated soil.

ANTIBACTERIAL AND ANTIFUNGAL EFFECT OF ACHILLEA MILLEFOLIUM ESSENTIAL OIL DURING SHELF LIFE OF MAYONNAISE

The importance of food-borne disease and consumer demands for avoiding synthetic food preservatives shifted the research interest to natural food preservatives such as essential oils which have antimicrobial activity. Also, spoilage of foods by fungi is a major problem, especially in developing countries. The aim of this study was to evaluate the efficiency of Achillea millefolium essential oil as natural food preservative in high fat and low fat mayonnaise kept at 4°C for 6 months. Mayonnaise samples were divided into four experimental treatments, namely: EO (essential oil in concentrations of 0.45-7.2 mg/ml), BS (sodium benzoate and potassium sorbate in concentration of 0.75 mg/ml), Cmo (control: no preservative with added microorganisms) and C (control: no preservative and no added microorganisms). The results showed that of essential oil of Achillea millefolium had influence against all of the tested microorganisms in mayonnaise and all of the pathogens and fungi did not grow in mayonnaise, whereas in the control samples all of the microorganisms grew. The maximum cell counts of bacteria and fungus in low fat mayonnaise were approximately lower than the high fat mayonnaise or resistance to inactivation of microorganisms appeared to be greater in high fat mayonnaise than in low fat mayonnaise (p< 0.05). Also, BS samples exhibited antimicrobial properties against tested species during storage. In conclusion the essential oil of Achillea millefolium would lead to control food pathogenic organisms and food spoilage organisms and therefore, it can be used as natural preservative in food industry such as mayonnaise.

Survivability of Probiotic Bacteria in Model Systems of Non-Fermented and Fermented Coconut and Hemp Milks

This study aimed at determining the survivability of probiotic bacteria cultures in model non-dairy beverages subjected or not to the fermentation and storage processes, representing milk substitutes. The experimental material included milks produced from desiccated coconut and non-dehulled seeds of hemp (Cannabis sativa L.). The plant milks were subjected to chemical and microbiological evaluation immediately after preparation as well as on day 7, 14, and 21 of their cold storage. Study results proved that the produced and modified plant non-dairy beverages could be the matrix for probiotic bacteria. The fermentation process contributed to increased survivability of Lactobacillus casei subsp. rhamnosus in both coconut and hemp milk. During 21-day storage of inoculated milk substitutes, the best survivability of Lactobacillus casei was determined in the fermented coconut milk. On day 21 of cold storage, the number of viable Lactobacillus casei cells in the fermented coconut and hemp milks ensured meeting the therapeutic criterion. Due to their nutritional composition and cell count of bacteria having a beneficial effect on the human body, the analyzed groceries—offering an alternative to milk—represent a category of novel food products and their manufacture will contribute to the sustainable development of food production and to food security assurance.

Evaluation of fermentation conditions to improve the sensory quality of broomcorn millet sour porridge

This study aimed to evaluate the use of three strains, namely, Lactobacillus brevis L1, Acetobacter aceti A1 and Saccharomyces cerevisiae E4, as inocula for the fermentation of broomcorn millet sour porridge, and the effect of different conditions on sour porridge fermentation. Results showed that these three strains were all suitable for the broomcorn millet sour porridge fermentation, and the combination of L1, A1 and E4 (1∶1∶1, v/v/v) was the best combination of strains starter. The optimal fermentation conditions were liquid-to-solid ratio of 3.33 (v/w), inoculum size of 4.71% (v/v), fermentation time of 31.94 h and fermentation temperature of 30.47 °C. In the verification experiment, the sensory evaluation score of sour porridge was extremely close to the predicted value, and the sensory evaluation was the following: milk white, sour smell, millet taste and soft, and the titratable acidity was 74.5 °T. The viable cell counts of bacteria and yeast surviving in the sour porridge were 2.3 × 1012 and 1.4 × 1011 CFU/mL, respectively.

Antimicrobial Coatings from Hybrid Nanoparticles of Biocompatible and Antimicrobial Polymers.

Hybrid nanoparticles of poly(methylmethacrylate) synthesized in the presence of poly (diallyldimethyl ammonium) chloride by emulsion polymerization exhibited good colloidal stability, physical properties, and antimicrobial activity but their synthesis yielded poor conversion. Here we create antimicrobial coatings from casting and drying of the nanoparticles dispersions onto model surfaces such as those of silicon wafers, glass coverslips, or polystyrene sheets and optimize conversion using additional stabilizers such as cetyltrimethyl ammonium bromide, dioctadecyldimethyl ammonium bromide, or soybean lecithin during nanoparticles synthesis. Methodology included dynamic light scattering, determination of wettability, ellipsometry of spin-coated films, scanning electron microscopy, and determination of colony forming unities (log CFU/mL) of bacteria after 1 h interaction with the coatings. The additional lipids and surfactants indeed improved nanoparticle synthesis, substantially increasing the conversion rates by stabilizing the monomer droplets in dispersion during the polymerization. The coatings obtained by spin-coating or casting of the nanoparticles dispersions onto silicon wafers were hydrophilic with contact angles increasing with the amount of the cationic polymer in the nanoparticles. Against Escherichia coli and Staphylococcus aureus, bacteria cell counts were reduced by approximately 7 logs upon interaction with the coatings, revealing their potential for several biotechnological and biomedical applications.

Growth and survival of Lactobacillus casei in rice bran and banana peel medium

The aim of this study is to evaluate the effect of different types of lignocellulose biomass as a carbon source on the growth and survival of Lactobacillus casei. The microbe was grown as a pure culture in three types of media, such as rice bran, banana peel and MRS medium. Rice bran (RB) and banana peel (BP) were kept at 121°C for 15 minutes and the extraction was conducted to collect the turbid liquid to be used as a medium for the fermentation. The medium was inoculated with 22 hours old inoculum culture at 37°C. The viable cell counts of bacteria (log10 CFU/mL), cell dry weight measurement (g cdw/L), pH and glucose content (g/L) were monitored and recorded during the fermentation. The performance of the fermentation was analysed and compared in terms of biomass produced and cell viability. The finding indicates that banana peel medium (8.78 g/L) contains a higher sugar content compared to rice bran medium (3.42 g/L). However, the growth and survival of Lactobacillus casei are better in rice bran medium. The highest biomass produced in rice bran medium was 3.8 g cdw/L and the maximum cell viability of L. casei in rice bran medium was 7.48 log10 CFU/mL.

Growth and survival of Lactobacillus casei in rice bran and banana peel medium

The aim of this study is to evaluate the effect of different types of lignocellulose biomass as a carbon source on the growth and survival of Lactobacillus casei. The microbe was grown as a pure culture in three types of media, such as rice bran, banana peel and MRS medium. Rice bran (RB) and banana peel (BP) were kept at 121°C for 15 minutes and the extraction was conducted to collect the turbid liquid to be used as a medium for the fermentation. The medium was inoculated with 22 hours old inoculum culture at 37°C. The viable cell counts of bacteria (log10 CFU/mL), cell dry weight measurement (g cdw/L), pH and glucose content (g/L) were monitored and recorded during the fermentation. The performance of the fermentation was analysed and compared in terms of biomass produced and cell viability. The finding indicates that banana peel medium (8.78 g/L) contains a higher sugar content compared to rice bran medium (3.42 g/L). However, the growth and survival of Lactobacillus casei are better in rice bran medium. The highest biomass produced in rice bran medium was 3.8 g cdw/L and the maximum cell viability of L. casei in rice bran medium was 7.48 log10 CFU/mL.

The increased viability of probiotic Lactobacillus salivarius NRRL B-30514 encapsulated in emulsions with multiple lipid-protein-pectin layers

Probiotics have demonstrated various health benefits but have poor stability to sustain food processing and storage conditions, as well as after ingestion. Biopolymer beads are commonly studied to encapsulate probiotic cells to improve their stability, but the millimeter-dimension of these beads may not meet the quality requirement of food products. The aim of this study was to enhance the viability of Lactobacillus salivarius NRRL B-30514 by encapsulation in emulsion droplets with multiple lipid-protein-pectin layers. Spray-dried L. salivarius was suspended in melted anhydrous milk fat that was then emulsified in a neutral aqueous phase with whey protein isolate or sodium caseinate to prepare primary solid/oil/water (S/O/W) emulsions. Subsequently, pectin was electrostatically deposited onto the droplet surface at pH3.0 to form secondary emulsions. The encapsulation efficiency was up to 90%. After 20-day storage at 4°C, the viable cell counts of bacteria in secondary emulsions at pH3.0 and primary emulsions at 7.0 were 3 log higher than the respective free cell controls. After heating at 63°C for 30min, free L. salivarius was inactivated to be undetectable, while about 2.0logCFU/mL was observed for primary (at pH7.0) and secondary (at pH3.0) emulsion treatments. Additionally, a 5log-CFU/g-powder reduction was observed after spray drying free L. salivarius, while a 2logCFU/g reduction was observed for emulsion treatments with capsules smaller than 20μm. Furthermore, cross-linking the secondary emulsion with calcium enhanced the viability of L. salivarius after the simulated gastric and intestinal digestions. Therefore, the studied S/O/W emulsion systems may be used to improve the viability of probiotics during processing, storage, and gastrointestinal digestion.

Effect of Meteorological Condition and Temperature Humidity Index (THI) on Milk Quality of Holstein Cow

Increasing in ambient temperature by global warming is likely to reduce milk yields and negatively affect milk quality in dairy cows. The projected increase in temperature would impact on dairy industry since production costs would increase with reductions in milk production. In Korea, dairy farmers are paid according to the composition of the raw milk components (milk fat concentrations, somatic cell counts and bacteria cell counts). In this study, to assess changes of milk quality caused by ambient temperature and relative humidity in the southern part of Korea (Gyeongbuk province), the temperature-humidity index (THI) was calculated on the base of the equation suggested by Schoen's model. Correlation and regression analysis were performed to determine the effects of the temperature, relative humidity and THI on milk quality. Increased Corresponding author: Jin Wook Kim Tel : +82-55-772-1885 Fax : +82-55-772-1889 E-mail : jinkim@gnu.ac.kr 156 ... Journal of Agriculture & Life Science 47(6) temperature and THI significantly reduced milk fat concentrations from 4.0-4.1% during the winter to 3.6-3.7% during the summer. Occurrence ratio of the 1st grade somatic cell counts (1 SCC) was lower during April to September compared to that of annual average. The THI was negatively correlated to milk fat concentrations (r=-0.8914) and 1 SCC (r=-0.6067) in the overall Gyeongbuk region. There were significant effects of the temperature and THI on milk fat concentrations and 1 SCC. Whereas occurrence ratio of 1A bacteria cell counts (1 BC) had no correlation with the temperature, relative humidity and THI. To make predictions for milk fat concentrations and 1 SCC, the regression model was developed to fit data. Overall, these results suggest that the THI is a useful and easy way to assess the risks of heat stress and is a candidate parameter to predict milk quality.

시판막걸리의 저장기간에 따른 품질 특성 및 미생물의 변화

시판되는 막걸리 3종을 <TEX>$10^{\circ}C$</TEX>와 <TEX>$25^{\circ}C$</TEX>에 저장하며 이화학적 특성과 미생물의 변화를 분석하였다. <TEX>$10^{\circ}C$</TEX>에서 저장한 막걸리의 에탄올 함량은 11일 동안 7.0%를 넘지 않았으며 pH는 3.12-3.99, 총산은 0.22-0.28%였으며 고형분 함량은 저장기간 동안 감소는 것으로 나타났다. <TEX>$25^{\circ}C$</TEX>에서 저장 한 막걸리의 에탄올 함량은 저장 9일에 7.0%를 초과하였으며 pH와 총산은 각각 3.96-4.17과 0.27-0.30%로 <TEX>$10^{\circ}C$</TEX>에 저장 한 막걸리 보다 높게 나타났으며 고형분 함량은 큰 폭으로 감소하였다. 저장 기간 동안의 효모수는 <TEX>$10^{\circ}C$</TEX>와 <TEX>$25^{\circ}C$</TEX>에 저장 시 각각 저장 3일과 1일에 <TEX>$2.90-16.00{\times}10^7$</TEX> CFU/mL와 <TEX>$1.12-29.40{\times}10^7$</TEX> CFU/mL로 최대치를 보였으며 세균수는 <TEX>$25^{\circ}C$</TEX>에 저장 한 막걸리가 <TEX>$10^{\circ}C$</TEX>에 저장한 막걸리에 비하여 높은 것으로 나타났다. 젖산균은 저장 3-7일 높게 나타났는데 <TEX>$25^{\circ}C$</TEX>에서 저장한 막걸리에서 <TEX>$38.90-50.00{\times}10^7$</TEX> CFU/mL로 <TEX>$10^{\circ}C$</TEX>에 저장 한 막걸리에 비하여 더 높게 검출되었다. 기호도 검사 결과 <TEX>$25^{\circ}C$</TEX>에 저장 한 막걸리는 저장 1일 이후부터 5.0 이하의 점수를 보였으며 <TEX>$10^{\circ}C$</TEX>에 저장 한 막걸리는 저장 11일 후에도 4.9-5.2 수준을 나타내었다. The aim of this study was to determine changes of physicochemical properties and microorganisms of commercial Makgeolli during storage at <TEX>$10^{\circ}C$</TEX> and <TEX>$25^{\circ}C$</TEX> During storage at <TEX>$10^{\circ}C$</TEX> for 11 days, ethanol contents did not increased up to 7.0%, and pH and total acidity were ranged with 3.12-3.99 and 0.22-0.28%, respectively. Makgeolli which was storaged at <TEX>$25^{\circ}C$</TEX> for 11 days showed more than 7.0% of alcohol contents, pH of 3.96-4.17 and total acidity of 0.27-0.30%. Yeast cell counts showed maximal <TEX>$2.90-16.00{\times}10^7$</TEX> CFU/mL at <TEX>$10^{\circ}C$</TEX> for 3 days and <TEX>$1.12-29.40{\times}10^7$</TEX> CFU/mL at <TEX>$25^{\circ}C$</TEX> for 1 day. Lactic acid bacteria and total bacteria cell counts of Makgeolli which was storaged at <TEX>$25^{\circ}C$</TEX> for 11 days were higher than those <TEX>$10^{\circ}C$</TEX> storage. In preference test, Makgeolli from storage at <TEX>$10^{\circ}C$</TEX> for 11 days was showed the level of 4.9-5.2 points however, Makgeolli from storage at <TEX>$25^{\circ}C$</TEX> for one day showed below 5.0 point.

A method for high throughput determination of viable bacteria cell counts in 96-well plates

BackgroundThere are several methods for quantitating bacterial cells, each with advantages and disadvantages. The most common method is bacterial plating, which has the advantage of allowing live cell assessment through colony forming unit (CFU) counts but is not well suited for high throughput screening (HTS). On the other hand, spectrophotometry is adaptable to HTS applications but does not differentiate between dead and living bacteria and has low sensitivity.ResultsHere, we report a bacterial cell counting method termed Start Growth Time (SGT) that allows rapid and serial quantification of the absolute or relative number of live cells in a bacterial culture in a high throughput manner. We combined the methodology of quantitative polymerase chain reaction (qPCR) calculations with a previously described qualitative method of bacterial growth determination to develop an improved quantitative method. We show that SGT detects only live bacteria and is sensitive enough to differentiate between 40 and 400 cells/mL. SGT is based on the re-growth time required by a growing cell culture to reach a threshold, and the notion that this time is proportional to the number of cells in the initial inoculum. We show several applications of SGT, including assessment of antibiotic effects on cell viability and determination of an antibiotic tolerant subpopulation fraction within a cell population. SGT results do not differ significantly from results obtained by CFU counts.ConclusionSGT is a relatively quick, highly sensitive, reproducible and non-laborious method that can be used in HTS settings to longitudinally assess live cells in bacterial cell cultures.

Changes in growth and survival of Bifidobacterium by coculture with Propionibacterium in soy milk, cow's milk, and modified MRS medium

Bifidobacterium adolescentis Int57 (Int57) and Propionibacterium freudenreichii subsp. shermanii ATCC 13673 (ATCC 13673) were grown either in coculture or as pure cultures in different media, such as cow's milk, soybean milk, and modified MRS medium. The viable cell counts of bacteria, changes in pH, concentrations of organic acids, and contents of various sugars were analyzed during incubation up to 7days. In soy milk, the survival of cocultured Int57 was six times higher than the monocultured cells, and ATCC 13673 cocultured with Int57 consumed 69.4% of lactic acid produced by Int57 at the end of fermentation. In cow's milk, coculture with ATCC 13673 increased the growth of Int57 from 24h until 120h by approximately tenfold and did not affect the survival of Int57 cells. After 96h of fermentation of modified MRS, the survival of ATCC 13673 cells cocultured with Int57 increased by 3.2- to 7.4-folds as compared with ATCC 13673 monoculture, whereas the growth of Int57 cells was unaffected. The growth and metabolic patterns of two strains during coculture showed noticeable differences between food grade media and laboratory media. The consumption of stachyose in soy milk during coculture of Int57 with ATCC 13673 was increased by more than twice compared with Int57 monoculture, and completed within 24h. The combinational use of Bifidobacterium and Propionibacterium could be applied to the development of fermented milk or soy milk products.

전통 막걸리의 저장중 효모와 세균의 변화

한국 전통 생 막걸리의 최적 저장 조건을 확립하기 위하여 먼저 전통 생 막걸리를 제조한 후 <TEX>$4^{\circ}C$</TEX>와 <TEX>$20^{\circ}C$</TEX>에 저장하면서 효모와 총 세균, 젖산균 수의 변화를 조사하였다. 효모는 <TEX>$20^{\circ}C$</TEX>에서 30일 저장 후 89%가 감소 되었으나, <TEX>$4^{\circ}C$</TEX>저장에서는 큰 변화가 없었다. 총 세균수는 <TEX>$20^{\circ}C$</TEX>에서 30일 저장시 98.0%가 감소 되었고 젖산균 역시 99%가 감소되었다. 그러나 <TEX>$4^{\circ}C$</TEX>저장에서는 65%미만의 낮은 감소를 보였다. 위의 결과와 관능검사 결과 등을 종합하였을 때 본 연구에서 제조한 생 막걸리는 <TEX>$4^{\circ}C$</TEX>와 <TEX>$20^{\circ}C$</TEX>에서 15일까지도 큰 품질저하 없이 음용할 수 있는 상태로 저장이 가능한 것으로 판단된다. In order to optimize storage conditions of Korean traditional Makgeolli, we brewed Korean traditional Makgeolli for 1 week with two-stage fermentations and investigated changes viable cell counts of yeasts and bacteria during storage for 1 month at <TEX>$4^{\circ}C$</TEX> and <TEX>$20^{\circ}C$</TEX>. Yeast viable cell counts were decreased to 89.0% after storage for 30 days at <TEX>$20^{\circ}C$</TEX>, however, those were not significantly changed at <TEX>$4^{\circ}C$</TEX> storage. Bacteria cell counts were decreased to 59.0% of initial cell counts for 30 days at <TEX>$4^{\circ}C$</TEX>. In the storage at <TEX>$20^{\circ}C$</TEX>, bacteria were significantly decreased to 98.0% of initial cell counts after storage for 30 days. Lactic acid bacteria were also similar to those of total bacteria cell counts at <TEX>$4^{\circ}C$</TEX> storage, however, 99% of lactic acid bacteria were decreased at <TEX>$20^{\circ}C$</TEX> storage for 30 days.

PREPARATION AND PROPERTIES OF ANTIBACTERIAL ALGINATE FILMS INCORPORATING EXTRUDED WHITE GINSENG EXTRACT

ABSTRACT Preparation of antibacterial alginate films incorporating extruded white ginseng (EWG) extracts was attempted. The antibacterial effect of EWG extract on six selected food pathogenic bacteria was compared with the effect of red ginseng (RG) and white ginseng (WG) extracts. The EWG was processed in a twin-screw extruder with feed moisture of 20% and barrel temperature of 115 and 130C. The data obtained by agar diffusion assay demonstrated that the film containing 1 g/mL of EWG at barrel temperatures of 115 (EWG-115) and 130C (EWG-130) exhibited stronger antibacterial activity against the four strains of bacteria than the other extracts RG and WG. All films sampled showed reduction in bacteria cell counts (log cycle) compared with the control. After 24 h of incubation, Pseudomonas aeruginosa, Bacillus subtilis and Listeria monocytogenes showed the lowest count in films incorporating EWG-115; the cell reductions were 9.1, 7.46 and 8.31 log cfu/mL, respectively. PRACTICAL APPLICATIONS Extrusion technology has the practical benefit of achieving a uniform product quality and higher productivity. Developing a ginseng antibacterial film will benefit the Korean food system by ensuring healthy foods. Films containing extruded ginseng extracts were more effective against bacteria than those containing red or white ginseng. Overall, this study provides the knowledge needed to interpret ginseng-based antimicrobial edible or food packaging films.

Rapid molecular methods for enumeration and taxonomical identification of acetic acid bacteria responsible for submerged vinegar production

The aim of the present study was to search for a rapid and reliable method to enumerate viable acetic acid bacteria (AAB) and to identify to genera and species level AAB isolates from vinegars in full acetic fermentation elaborated by the submerged method from cider, wine and spirit ethanol in industrial bioreactors. Results showed that the rapid epifluorescence staining method using the LIVE/DEAD BacLight bacterial viability kit and direct counts in Neubauer chamber rendered consistent and reliable data for viable cell counts of bacteria in all the studied vinegars. A linear correlation was shown between viable cell counts and fermentation rates. The highest fermentation rates and viable cell counts were found in cider vinegars, whereas spirit vinegars showed the lowest values for both parameters. Eighty-four AAB pure isolates were recovered from 41 different vinegar samples and were submitted to DNA extraction. PCR amplification of the 16S–23S intergenic spacer region of rDNA and subsequent sequencing were carried out to identify isolates to species level. Results showed that Gluconacetobacter europaeus was the predominant cultivable species, appearing in 79% of the total isolates. This was the unique species found in spirit vinegars, and this is the first time that AAB from spirit vinegars are taxonomically identified. Ga. europaeus was as well the predominant cultivable species in white wine vinegars. Cider vinegars presented the highest variability of species: Ga. europaeus (35.3% appearance among cultivable isolates), Ga. xylinus (35.3%), Acetobacter pasteurianus (17.6%) and Ga. hansenii (11.8%). Red wine vinegars showed cultivable isolates of the species Ga. xylinus (71.4%) and Ga. europaeus (28.6%). Summarising, both described methods for AAB enumeration and taxonomical identification proved to be fast and reliable methods, and results revealed Ga. europaeus as the cultivable major species in vinegars in full fermentation conducted by the submerged method, suggesting that Ga. europaeus strains can constitute excellent starter cultures for the elaboration of vinegars by the submerged method.

Effect of gamma irradiation on Burkholderia thailandensis ( Burkholderia pseudomallei surrogate) survival under combinations of pH and NaCl

This study evaluated the effect of gamma irradiation on Burkholderia thailandensis ( Burkholderia pseudomallei surrogate; potential bioterrorism agent) survival under different levels of NaCl and pH. B. thailandensis in Luria Bertani broth supplemented with NaCl (0–3%), and pH-adjusted to 4–7 was treated with gamma irradiation (0–0.5 kGy). Surviving cell counts of bacteria were then enumerated on tryptic soy agar. Data for the cell counts were also used to calculate D 10 values (the dose required to reduce 1 log CFU/mL of B. thailandensis). Cell counts of B. thailandensis were decreased ( P<0.05) as irradiation dose increased, and no differences ( P≥0.05) in cell counts of the bacteria were observed among different levels of NaCl and pH. D 10 values ranged from 0.04 to 0.07 kGy, regardless of NaCl and pH level. These results indicate that low doses of gamma irradiation should be a useful treatment in decreasing the potential bioterrorism bacteria, which may possibly infect humans through foods.