• Title/Summary/Keyword: lag-phase

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Evaluation of the Degradation of Carbohydrate-based Material During Anaerobic Digestion for High-efficiency Biogas Production

  • Kim, Min-Jee;Kim, Sang-Hun
    • Journal of Biosystems Engineering
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    • v.43 no.2
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    • pp.110-118
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    • 2018
  • Purpose: In this study, the potential for biogas production, degradation rates, and lag-phase of diauxic growth of carbohydrate-based material, which is one of the proximate compositions, were investigated. Methods: This study was conducted using starch as a carbohydrate-based material. In experimental condition 1, the biogas potential of carbohydrate-based material was measured. In experimental condition 2, the effect of feed to microorganism ratio (F/M ratio) on lag-phase of diauxic growth from carbohydrate-based material was tested. Biochemical methane potential tests were performed at five different feed to microorganism ratios (0.2, 0.4, 0.6, 0.8, and 1.0) under mesophilic conditions. The biogas production patterns, lag-phase, total volatile fatty acids to total alkalinity ratio (TVFA/TA ratio), and time required for 90 percent biogas production were used to evaluate biogas production based on the biochemical methane potential tests. Results: In experimental condition 1, unlike previous studies, biogas was produced in the TVFA/TA ratio ranging from 1.131 to 2.029 (approximately 13-19 days). The methane content in the biogas produced from the digesters was 7% on day 9 and increased rapidly until approximately day 27 (approximately 72%). In experimental condition 2, biogas yield was improved when the feed to microorganism ratio exceeded 0.6, with an initial lag-phase. Conclusions: Even if the TVFA/TA ratio was greater than 1.0, the biogas production was processed continuously, and the $CO_2$ content of the biogas production was as high as 60%. The biogas yield was improved when the F/M ratio was increased more than 0.6, but the lag-phase of carbohydrate-based material digestion became longer starting with high organic loading rate. To clarify the problem of the initial lag-phase, our future study will examine the microbial mechanisms during anaerobic digestion.

Study on Confirmation of Solid-Meal Lag Phase of Gastric Emptying (고형음식물 위배출시 초기 정체기의 존재에 대한 연구)

  • Lee, Ji-Young;Lee, Kyoung-Soo;Kim, Chang-Guhn;Juhng, Seon-Kwan;Won, Jong-Jin;Nah, Yong-Ho
    • The Korean Journal of Nuclear Medicine
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    • v.25 no.2
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    • pp.207-210
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    • 1991
  • The purpose of this study was to examine the existence of a lag phase of gastric emptying of solid meals. We studied solid phase gastric emptying in 26 normal subject using continuous data aquisition for 30 minutes. Each ingested a 300 g meal containing $^{99m}Tc-labeled$ scrambled egg (solid 150g, milk 150 ml). Lag phase was determined by 1) inspection of the gastric emptying curve 2) time to a 2% decrease in stomach activity 3) the time of visual appearance of duodenal activity on computer image We concluded that solid meal lag phase exist.

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Effect of operational pH on anaerobic hydrogen fermentation of food waste (음식폐기물의 혐기성 수소 발효시 운전 pH의 영향)

  • Lee, Chae-Young;Lee, Se-Wook
    • Journal of the Korea Organic Resources Recycling Association
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    • v.19 no.3
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    • pp.73-78
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    • 2011
  • The pH is one of the most important factors affecting metabolism pathway and activity of hydrogen producing bacteria. The effect of operational pH on anaerobic hydrogen fermentation of food waste was evaluated at mesophilic condition. In this batch experiment, the initial pH was 8.0 and the operational pH was controlled at 4.7~7.0 by the addition of 5N KOH solutions. At the operational pH of 4.7, the lag phase and the maximum hydrogen production were 47.9h and 534.4 mL, respectively. The lag phase and the maximum hydrogen production were decreased as the operational pH increased. At the operational pH of 7.0, the lag phase and the maximum hydrogen production were 4.2 h and 213.8 mL, respectively.

Growth and Cadmium Removal in Recombinant Saccharomyces cerevisiae Harboring A Metallothionein Gene (Metallothionein 유전자가 도입된 재조합 Saccharomyces cerevisiae의 생육과 카드뮴 제거)

  • 김대옥;박성식서진호
    • KSBB Journal
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    • v.11 no.5
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    • pp.543-549
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    • 1996
  • Recombinant Saccharomyces cerevisiae BZ-pJ containing the gene coding for metallothionein, a metalbinding protein was grown in the medium with high cadmium concentrations to study the characteristics of growth and cadmium uptake. High concentrations of cadmium reduced cell growth and final cell density and increased the lag phase periods of the recombinant yeast. Addition of 10 mg $Cd^{2+}$/L to the growth medium remarkably decreased a lag period and enhanced the specific cadmium uptake to 52.6 mg $Cd^{2+}$/g dry cell. The effect of copper addition was further investigated in the medium of 680 mg Cd2+/L. An increase in copper concentration from 11.0 to 33.3 mg/L enhanced the specific cadmium uptake from 17.0 to 42.0 mg Cd2+/g dry cell.

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Nutritional Studies on the Growth of the Rapamycin-Producing Streptomyces hygroscopicus

  • Kim, Wan-Seop;Davis, Sean;Wong, Grace;Demain, Arnold-L.
    • Journal of Microbiology and Biotechnology
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    • v.13 no.4
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    • pp.560-563
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    • 2003
  • During our previous studies on the relationship between nutrient requirements of S. hygroscopicus C9 and rapamycin biosynthesis, we developed chemically-defined media containing among other nutrients, aspartic acid, arginine, histidine, or ammonium sulfate. However, these media (“Cheng et al. medium” and “Lee et al. medium”) showed very slow growth characterized by a very long lag phase of growth. In an attempt to develop a chemically-defined or semi-defined medium to support more rapid growth and increased cell production, we have carried out studies to shorten the lag phase. Of the various additives tested, vitamin-free casein acid hydrolysate was the most significant by shortening the lag phase by 2-3 days. Mixtures of amino acids failed to replace casein acid hydrolysate. The active principle passed through an ultrafilter with a molecular weight cutoff of 1,000 and thus may be a peptide. The present work has yielded a semi-defined medium which should be useful for further growth studies on S. hygroscopicus C9.

Biogas Production Performance Based on Carbon Number and Double Bond Count of Long-chain Fatty Acids

  • Kim, Soo-Ah;Kim, Sang-Hun
    • Journal of Biosystems Engineering
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    • v.43 no.1
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    • pp.37-44
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    • 2018
  • Purpose: The objective of this study was to investigate the high-efficiency anaerobic digestion of organic wastes with high fat content. Specifically, the analysis focused on biogas production performance with a focus on carbon number and the double bond count of the long-chain fatty acids (LCFAs), which are hydrolysis products of triglycerides. Methods: Experiments were performed under mesophilic anaerobic conditions with a feed-to-microorganism ratio (F/M) of 1.0. Biogas production performance was analyzed through biogas production patterns, lag-phase, and the time required for 90% biogas production (T90). Results: Biogas production increased when the content of unsaturated LCFAs (containing relatively large numbers of carbon atoms) increased. In substrate containing LCFAs with four or more double bonds, although the initial lag-phase in biogas production was shortened, development of a three-step lag-phase resulted in decreased biogas production. These results suggest that high rates of anaerobic digestion are possible when the LCFAs have high unsaturated fatty acid content with three or fewer double bonds. Conclusions: When various types of LCFAs are digested anaerobically, biogas production performance can be improved if the unsaturated fatty acid content and number of double bonds are optimized for maximum production.

황환원 세균의 quorum-sensing 유사 현상

  • Park, Ji-Eun;Jang, Deok-Jin
    • 한국생물공학회:학술대회논문집
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    • 2001.11a
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    • pp.545-548
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    • 2001
  • Microbiologically influenced corrosion (MIC) of metal is common in the natural environment and sulfate reducing bacteria are representative microorganisms for MIC. We found that biofilm fomlation by SRB on the metal surface might be controlled by quorum sensing, which is a cell density dependent regulation of cell metabolism. As cell free culture fluids (spent media) of Desulfovibrio vulgaris and D. desulfuricans were tested for quontrn sensing related test strains, it was found that spent media of two SRB induced increased luminescence of Vibrio harveyi BB886 (sensor 1+, sensor 2-) and BB170 (sensor 1-, sensor 2+). Quorum activities of D. vulgaris and D. desulfuricans appeared to be parallel to growth patterns, i.e., it was low in the lag phase, highly increased in the exponential phase, and reached maximum in the stationary phase. Interestingly, however, luminescence of V. harveyi BB886 and BB170 induced by a unit cell mass of the SHB showed a maximal peak in the late lag phase. Hence, it was suspected that quorum sensing of these two SHB play unknown roles in shifting cells from dormant to growth stages.

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Physiological Responses of Bacillus amyloliquefaciens Spores to High Pressure

  • Ahn, Ju-Hee;Balasubramaniam, V.M.
    • Journal of Microbiology and Biotechnology
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    • v.17 no.3
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    • pp.524-529
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    • 2007
  • Pressure inactivation behavior of Bacillus amyloliquefaciens spores was investigated in deionized water. The spores of B. amyloliquefaciens were subjected to $105^{\circ}C$ and 700 MPa. The magnitude of the decrease in viability after pressure treatment was similar to that after pressure treatment followed by heat shock. The increase of dipicolinic acid (DPA) release was correlated with the spore inactivation, and the hydrophobicity did not significantly change during the pressure-assisted thermal processing (PATP). Lag phase duration increased with increasing pressure process time. The mechanisms of spore germination and inactivation during the PATP were related to a complex physiological process.

Effects of chlorine and chlorine compounds on morphology and function of Caulobacter cells (Caulobacter의 세포(細胞)의 형태(形態) 및 기능(機能)의 분화(分化)에 대한 염소 및 염소화합물의 영향(影響))

  • Kim, Chi-Kyung;Park, Moon-Kook;Yum, Kon
    • Applied Microscopy
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    • v.12 no.1
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    • pp.23-32
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    • 1982
  • Caulubacter is distinctive in the morphology and replication and ubiquitous in the biosphere, especially in every type of aquatic environment. In water and waste-water treatment processes, chlorine and chlorine compounds have been used as a main disinfectant throughout the world. Therefore, Caulobacter in the waters should be affected by chlorination of the waters. The objective of this study is to determine the effects of the disinfectants on Caulobacter cells and on the developmental processes of the cells. The Caulobacter swarmer cells were disinfected by chlorine at pH 7.0 minutes of the reaction with 2.0 mg/l of infected at pH 10.0. The swarmer cells treated with 2.0 or 4.0 mg/l of chlorine for 15 minutes lost their flagella and were observed by electron microscopy to be damaged on their cell surfaces, discharging some cellular materials. When the chlorinated swarmers and untreated control samples were recultivated in fresh PYE broth medium, the control swarmers multiplicated exponentially after one-hour lag phase, whereas the chlorinated swarmers extended the lag phase to about four hours. During the extended lag phase, the cells were proved by electron microscopy to be grown and be in predivisional step, but no swarmer cell was found. When the stalked cells were chlorinated, almost all the cells were observed to have their stalks broken and some cellular materials discharged. In those samples recultivated, many cells differentiated to possess an abnormally elongated stalk with several crossbands on it. This suggests that the chlorine-shocked Caulobacter cells can develope to abnormal morphology in water environments which they can survive and regrow in.

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Alcohol Production by Extractive Fermentation in a Continuous Bioreactor (연속 생물반응기 안에서 유출 발효에 의한 알코올 생산)

  • 김재형;전순배이기영김동운
    • KSBB Journal
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    • v.4 no.1
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    • pp.21-30
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    • 1989
  • Lauryl alcohol was used as extracting solvent of ethanol, and its toxicity on the free cells or immobilized cells was tested. To increase ethanol productivity, extractive fermentation method combined with ethanol fermentation and ethanol recovery was applied to the immobilized batch and continuous fermenter. As the concentration of LaOH was increased, the lag phase became longer, but specific growth rate did not change greatly. And a cell entrapment technique could protect the yeast cells against both substrate inhibition and solvent toxicity. When the glucose concentration was 400 g/l and the LaOH/fermentation medium ratio was 4, total ethanol productivity increased with the enhancement of LaOH volume, and maximum productivity was 2.75 g/l.hr in the immobilized batch fermentation.

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