• Asian-Australasian Journal of Animal Sciences
• /
• v.11 no.4
• /
• pp.351-362
• /
• 1998

Microbial growth efficiency in the rumen was studied in sheep given hourly, 31.25 g oaten chaff with either 0.31 and 0.88 g urea or 1.88 and 5.63 g casein (exp. 1) and 33.33 g oaten chaff with 1.04 casein or 0.3, 0.6 and 0.9 g urea or the mixture of the casein and urea (exp. 2). Concentrations of ruminal fluid ammonia increased with increasing nitrogenous supplements. Organic matter digestibility in sacco in the rumen was not different irrespective of N sources. Isoacids and valeric acid increased with increasing ingested casein but decreased with increasing urea intake. Peptide and amino acid pools in ruminal fluid increased with increasing ammonia concentrations (exp. 2) suggesting that proteolytic activity and transportation of peptides and amino acids across microbial membrane of rumen microbes may be regulated by the metabolite mechanism (intracellular amino acids and $NH_4{^+}$, respectively). Densities of total viable and cellulolytic bacteria in ruminal fluid increased with increasing ammonia levels but that of small Entodinia decreased. The density of fungal sporangia growth on oat leaf blades decreased with increasing ammonia concentrations but appeared to remain constant in the presence of casein. Efficiency of net microbial cell synthesis was 15-28% higher when ammonia concentrations increased from 100 to above 200 mg N/l regardless of N sources. In conclusion, supplementation of preformed protein had no effect on rumen digestion and microbial growth efficiency. This could not be accounted for its effect on ruminal fluid ammonia. Increased microbial growth efficiency with increasing ammonia levels may be due to a reduction in the turnover of microbial cells within the rumen.

• Journal of Korean Society on Water Environment
• /
• v.26 no.4
• /
• pp.608-613
• /
• 2010

Electricity generation of microbial fuel cells (MFC) is greatly affected by the kind of feed substrates because substrates would change microbial community of electrochemically active bacteria (EAB) able to transfer electrons to electrode. The effect of different substrates on electricity generation and microbial community of MFC was investigated. Two-chamber MFCs fed with acetate (A-MFC), butyrate (B-MFC), propionate (P-MFC), glucose (G-MFC) and a mixture (M-MFC) of the 4 substrates (acetate : butyrate : propionate : glucose = 1 : 1 : 1 : 1 as $COD_{Cr}$ base) were operated under continuous mode. The maximum power density was found from the M-MFC ($190W/m^3$) which showed the lowest internal resistance ($89{\Omega}$). The maximum power densities of the pure substrates feed MFCs were in order of A-MFC ($25W/m^3$), P-MFC ($21W/m^3$), B-MFC ($20W/m^3$) and G-MFC ($9W/m^3$). In DGGE analysis, the microbial community structure in suspension was quite different from each others depending on feed substrates, while the community structure in the biofilm was relatively similar regardless of the substrates. This result suggests that the feed substrates would affect the microbial community of suspended growth bacteria than attached growth bacteria resulting in difference of electricity generation in MFCs.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.44 no.4
• /
• pp.325-331
• /
• 2011

Nonylphenol (NP), which is well known as an endocrine disrupter, has been detected widely in untreated sewage or waste water streams. Given the necessity of discovering an eco-friendly method of degrading this toxic organic compound, this study was conducted to isolate NP-degrading microorganisms from the aqueous environment. NP-degrading microbes were isolated through NP-containing enrichment culture. Finally, a microbial consortium, SW-3, capable of degrading NP with high efficiency, was selected from the mixture sample. The microbial consortium SW-3 was able to degrade over 99% of 100 ppm NP in the culture medium for 40 days at $25^{\circ}C$. The microbial consortium SW-3 seemed to utilize NP as a carbon source, since NP was the sole carbon source in the culture medium. In order to isolate the NP-degrading bacterium, we further conducted single colony isolation using the microbial consortium SW-3. Four strains isolated from SW-3 exhibited lower NP-degradation efficiency than that of SW-3, suggesting that NP was degraded by the co-metabolism of the microbial consortium. We suggest that the microbial consortium obtained in this study would be useful in developing an eco-friendly bioremediation technology for NP degradation.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.44 no.11
• /
• pp.1715-1724
• /
• 2015

The combined effects of a sanitizer mixture solution and antimicrobial ice on the quality of salted Chinese cabbages were examined. Salted Chinese cabbages were treated with a sanitizer mixture (comprised 50 ppm aqueous $ClO_2$ and 0.5% citric acid), packed in 2% brine and antimicrobial ice, and stored for 12 days at 4 and $10^{\circ}C$. Microbiological data on the salted Chinese cabbages after washing with the sanitizer mixture indicated that the populations of total aerobic bacteria, and yeast and molds decreased by 2.20 and 1.28 log CFU/g after treatment with the sanitizer mixture. In addition, coliforms population of salted Chinese cabbage after 12 days storage at $4^{\circ}C$ in the combined mixture of the sanitizer and antimicrobial ice was 3.22 log CFU/g, which was a significantly different from that of control (5.46 log CFU/g). The combined treatment of sanitizer mixture, antimicrobial ice, and low temperature at $4^{\circ}C$ suppressed reduction of pH and elevation of titratable acidity, resulting in delaying the growth of lactic acid bacteria. Differences in salinity, hardness, and Hunter's $L^*$, $a^*$, and $b^*$ values among treatments were negligible during storage at $4^{\circ}C$. Therefore, this study suggests that a combination of sanitizer mixture, antimicrobial ice treatment, and low temperature storage could improve the microbial safety and quality of salted Chinese cabbages during storage.

• Journal of Soil and Groundwater Environment
• /
• v.28 no.5
• /
• pp.12-24
• /
• 2023

The Songji lagoon is brackish environment with a mixture of saline and fresh water, and the interaction of groundwater-lagoon water creates a physicochemical gradient. Although some studies have been conducted on the hydrological and geochemical characteristics of the Songji lagoon, microbial ecological studies have not yet been conducted. In this study, we investigated the effect of groundwater and surface water interaction on water quality as well as microbial community changes in the Songji Lagoon using 16S rRNA gene sequencing. Hydrochemical analyses show that samples were classified as 5 hydrochemical facies (HF) and hydrochemical facies evolution (HFE) revealed the intrusion phase was more dominant (57.9%) than the freshening phase (42.1%). Higher microbial diversity was found in freshwater in comparison to saline water samples. The microbial community at the phylum level shows the most dominance of Proteobacteria with an average of 37.3%, followed by Bacteroidota, Actinobacteria, and Patescibacteria. Heat map analyses of the top 18 genera showed that samples were clustered into 5 groups based on type, and Pseudoalteromonas could be used potential indicator for seawater intrusion.

• Asian-Australasian Journal of Animal Sciences
• /
• v.13 no.8
• /
• pp.1084-1093
• /
• 2000

An in vitro gas production system was used to investigate the influence of various substrate mixtures on a natural mix of rumen microbes by measurement of fermentation end-products. The treatments were combinations of cassava (15.0, 30.0 and 45.0%) with different roughage sources (ruzi grass, rice straw or urea treated rice straw). Microbial biomass, net $^{15}N$ incorporation into cells, volatile fatty acid production, gas volume and rate of gas production increased linearly with increasing levels of cassava inclusion. There was also an effect of roughage source, with rice straw being associated with the lowest values for most parameters whilst similar values were obtained for ruzi grass and urea treated rice straw. The results suggest that microbial growth and fermentation rate increase as a function of readily available carbohydrate in the substrate mixture. A strong linear relationship between $^{15}N$ enrichment, total volatile fatty acid production and gas production kinetics support the suggestion of the use of the in vitro gas production system as a tool for screening feedstuffs as an initial stage of feed evaluation.

• Food Science of Animal Resources
• /
• v.37 no.4
• /
• pp.606-616
• /
• 2017

The objective of this research was to investigate the effects microbial transglutaminase (mTGs) on the physicochemical, microbial and sensory properties of kefir produced by using mix cow and soymilk. Kefir batches were prepared using 0, 0.5, 1 and 1.5 Units m-TGs for per g of milk protein. Adding m-TGs to milk caused an increase in the pH and viscosity and caused a decrease in titratable acidity and syneresis in the kefir samples. Total bacteria, lactobacilli and streptococci counts decreased, while yeast counts increased in all the samples during storage. Alcohols and acids compounds have increased in all the samples except in the control samples, while carbonyl compounds have decreased in all the samples during storage (1-30 d). The differences in the percentage of alcohols, carbonyl compounds and acids in total volatiles on the 1st and the 30th d of storage were observed at 8.47-23.52%, 6.94-25.46% and 59.64-63.69%, respectively. The consumer evaluation of the kefir samples showed that greater levels of acceptability were found for samples which had been added 1.5 U m-TGs for per g of milk protein.

• Journal of Periodontal and Implant Science
• /
• v.30 no.4
• /
• pp.725-736
• /
• 2000

It is becoming increasingly apparent that periodontitis consists of mixture of diseases, most of which respond favorably to traditional mechanical therapy. Among these variants of the disease, some appear to be associated with unusual microbial infections and defective host defenses. Many of these fail to respond to conventional treatment. The recognition that some forms of periodontitis are refractory to standard periodontal therapy has given rise to a new classification of peridontitis. A series of 1692 subgingival microbial samples sent to a diagnostic microbiology laboratory included 738 samples that could be identified as compatible with a clinical diagnosis of refractory or recurrent periodontitis. In descending order of prevalence the associated microbiota included Bacteroides forsythus(85%) ,Fusobacterium species(78%), Spirochetes(67%), Campylobacter rectus(64%), Porphyromonas gingivalis(59%), Peptostreptococcus micros(58%), motile rods(46%), Prevotella intermedia(33%), Eikenella corrodens(13%), Capnocytophaga species(12%) ,and Actinobacillus actinomycetemcomitans(6%). Antibiotic resistance to tetracycline, penicillin G, or metronidazole was particularly noticeable for Fusobacterium species, Capnocytophaga species, and Actinobacillus actinomycetemcomitans. It was largely absent for Campylobacter rectus. No antibiotic data were obtained for Porphyromonas gingivalis or Bacteroides forsythus, as these species were detected by immunofluorescence. The results indicate that a substantial number of microorganisms associated with refractory periodontitis are variably resistant to commonly-used antibiotics. Diagnostic microbiology must be considered an essential adjunct to the therapist faced with periodontal lesions refractory to conventional treatment.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.12
• /
• pp.1976-1982
• /
• 2007

In the current studies, we characterized the degradation of a hot mixture of benzene and toluene (BT) gases by a thermophilic biofilter using polyurethane as a packing material and high-temperature compost as a microbial source. We also examined the effect of supplementing the biofilter with yeast extract (YE). We found that YE substantially enhanced microbial activity in the thermophilic biofilter. The degrading activity of the biofilter supplied with YE was stable during long-term operation (approximately 100 d) without accumulating excess biomass. The maximum elimination capacity ($1,650\;g{\cdot} m^{-3}{\cdot} h^{-1}$) in the biofilter supplemented with YE was 3.5 times higher than that in the biofilter without YE ($470\;g{\cdot} m^{-3}{\cdot} h^{-1}$). At similar retention times, the capacity to eliminate BT for the YE-supplemented biofilter was higher than for previously reported mesophilic biofilters. Thus, thermophilic biofiltration can be used to degrade hydrophobic compounds such as a BT mixture. Finally, 168 rDNA polymerase chain reaction-DGGE (PCR-DGGE) fingerprinting revealed that the thermophilic bacteria in the biofilter included Rubrobacter sp. and Mycobacterium sp.

• 한국생물공학회:학술대회논문집
• /
• 2000.11a
• /
• pp.260-263
• /
• 2000

Membranes are widely used to separate target solute molecules such as proteins on the basis of their size in cell broth mixture to minimize the loss of target compounds. In this study, membrane separation system using ultrafilters of MWCO 100 K and 50 K, was operated for concentration and purification of microbial transglutaminase. Fermentation broth containing MTGase was prefiltered by using pore size 1.6 and $0.7\;{\mu}m$ pre-filter made of cellulose fiber and $0.45\;{\mu}m$ microfilter made of cellulose acetate. The prefiltered solution was concentrated by 100 K and 50 K ultrafilter. The final enzyme concentration was 1.29 units/ml and enzyme specific activity was 0.2 units/mg protein. This specific activity were 3.7 times higher than that of initial cell broth mixture. Membrane separation process of microfiltration and ultrafiltration was proved to be very economic, energy efficient and effective separation method used to concentrate MTGase.