• Journal of Hydrogen and New Energy
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• v.23 no.4
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• pp.397-403
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• 2012

Galactose, an isomer of glucose with an opposite hydroxyl group at the 4-carbon, is a major fermentable sugar in various promising feedstock for hydrogen production including red algal biomass. In this study, hydrogen production characteristics of galactose-glucose mixture were investigated using batch fermentation experiments with heat-treated digester sludge as inoclua. Galactose showed a hydogen yield compatible with glucose. However, more complicated metabolic steps for galactose utilization caused a slower hydrogen production rate. The existence of glucose aggravated the hydrogen production rate, which would result from the regulation of galactose-utilizing enzymes by glucose. Hydrogen produciton rate at galactose to glucose ratio of 8:2 or 6:4 was 67% of the production rate for galactose and 33% for glucose, which could need approximately 1.5 and 3 times longer hydraulic retention time than galacgtose only condition and glucose only condition, respectively, in continuous fermentation. Hydrogen production rate, Hydrogen yield, and organic acid production at galactose to glucose ratio of 8:2 or 6:4 were 0.14 mL H2/mL/hr, 0.78 mol $H_2$/mol sugar, and 11.89 g COD/L, respectively. Galactose-rich biomass could be usable for hydogen fermenation, however, the fermentation time should be allowed enough.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.225-234
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• 2006

Characteristics of electricity production from major fermentation products (acetate, propionate and butyrate) were evaluated in a microbial fuel cell (MFC). For each substrate, batch and continuous experiments were performed. The batch test result indicated that coulombic efficiency depended on the resistance connected in MFC circuit. With acetate, coulombic efficiency were 87% at $20{\Omega}$, but decreaced to 45% at$220{\Omega}$. In continuous tests, maximum power densities obtained was 220 Q with acetate. The maximum power densities of butyrate, acetate and propionate were 6.8, 6.1, and $5.2mW/m^2$, respectively. Propionate and butyrate were converted into acetate producing high currents. $H_2$ produced during butyrate and propionate probably used to produce electricity. In conclusion, butyrate conversion into acetate was faster than that of propionate with higher electricity production. If the production of propionate is inhibited during fermentation, anaerobically fermented liguor may be effectively applied for MFC.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.159-166
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• 2009

This study has been attempted to generate electricity, while simultaneously treating artificial organic wastewater using both batch and continuous microbial fuel cells (MFCs). In the batch MFC, current-voltage curve showed an onset potential of -0.69 V vs. Ag/AgCl. The potential range between this potential and 0 potential displayed an available voltage for an automatic production of electric energy and glucose, which was oxidized and treated at the same time. The 486 mg/L glucose solution showed the maximum power of $30mW/m^2$ and the maximum current density of $75mA/m^2$ shown in the power curve. As a result, discharging of the cell containing COD 423 mg/L at the constant current density of $60mA/m^2$ showed a continuous electricity generation for about 22 hours that dropped rapidly due to dissipating of organic material. Total electric energy production was 18.0 Wh. While discharging, the pH change was low and dropped from pH 6.53 to 6.20 then increased to 6.47, then stabilized at this charge. The COD treatment efficiency was found to be 72%. In the continuous MFC, COD removal tends to increase as the hydraulic retention time is increased. At one day of hydraulic retention time as the maximum value reaches the COD removal efficiency, power production rate and power production rate per COD removal that were obtained were 68.8%, $14mW/m^2$, and $20.8mW/m^2/g$ CODrm, respectively. In the continuous MFC, the power production rate per COD removal increases as the hydraulic retention time is increased and decreases as the organic loading rate is increased. At the values lower than an organic loading rate of $1kgCOD/m^3/d$, the values higher than about $18.1mW/m^2/g$ CODrm could be obtained.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.356-359
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• 2000

A two-stage fed-batch fermentation was carried out to increase xylitol productivity by Candida tropicalis. The first stage for cell growth was performed in the pH-stat and continuous fed-batch modes. The higher cell growth and lower ethanol production obtained in the fed-batch mode where the growth medium was fed when pH of culture broth increased over 5.7. And also the effect of oxygen transfer on xylitol production was investigated by changing agitation speed under 0.5 vvm of aeration. The maximum xylitol productivity and yield were obtained at 500 rpm of agitation.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.6
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• pp.599-602
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• 1997

Fluctuation of fungal zoospores on agar strips were observed in the rumen of sheep fed three different levels of dietary concentrate, timothy hay: concentrate = 3:0 (AF diet), timothy hay: concentrate = 2:1 (MC diet), timothy hay : concentrate = 1:2 (HC diet) respectively. The number of zoospores on the strip was drastically decreased after morning feed with AF diet. The number was the highest at 0 h ($1.34{\times}10^2/cm^2$), then declined to $2.0{\times}10^3/cm^2$ at 9 h after feeding. In the rumen of animals fed MC diet, the number of zoospores decreased with time after feeding, although the decrement was slower than that with AF diet. During 0-3 h after feeding, number of zoospores was $1.6{\times}10^4/cm^2$. Although the number slightly decreased at 6 and 9 h, relatively high levels were maintained. It seems that the inducers for zoospore-release were maintained at relatively high concentration throughout incubation period. The fluctuation pattern of number of germinated zoospores was different in the rumen of animals fed HC diet from those of AF and MC diets. The number of zoospores was constantly maintained at lower level ($1.0{\times}10^3/cm^2$) than the other diets. For MC diet, continuous high number of germinated zoospores may be due to the continuous release of zoospores by hemes in timothy hay and concentrate feed, and by unknown mechanisms. Unlike AF diet which promoted relatively rapid decline of zoosporogenesis, supplementation of concentrate feed to the timothy hay did not promote such rapid decline of zoosporogenesis. It was suggested that release of inducers for zoosporogenesis from concentrate feed persisted longer time than from timothy hay. HC diet promoted the lowest zoospore production, suggested the lowest fungal population size in this experiment. These results show that an appropriate amount of concentrate may support fungal growth and stimulate zoosporogenesis in the rumen.

• Asian-Australasian Journal of Animal Sciences
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• v.2 no.3
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• pp.411-412
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• 1989

• KSBB Journal
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• v.8 no.3
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• pp.217-223
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• 1993

Methods for production of ${\gamma}$-Polyglutamic acid( ${\gamma}$-PGA ) by an alkalophilic Alcaligenes sP. were investigated for batch and continuous culture processes. Both quantity and productivity of ${\gamma}$-PGA by Alcaligenes sp. in batch culture were gradually increased with the increase of glucose concentration up to 50g/l , but the maximal production yield of 63% was obtained at 10g/l of glucose concentration. The highest specific growth rate was about $0.25hr^{-1}$ at 50un of glucose concentration, and substrate inhibition was observed at above 50g1f of glucose concentration. The highest ${\gamma}$-PGA formation about 11g/l in a batch system was obtained at 31'C, pH 10.0 and 87rpn Productivity of 2.80g/l/hr for continuous cultivation was 9 times higher than the productivity for batch cultivation.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.299-306
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• 2005

Anaerobic fermentation of food waste (FW) and waste activated sludge (WAS) for hydrogen production was performed in CSTR (Continuous Stirred tank reactor) under various HRTs and volumetric mixing ratio (V/V) of two substrates, FW and WAS. The specific hydrogen production potential of FW was higher than that of WAS. However, pH drop in the CSTR for hydrogen production from FW was higher than that from WAS. The maintenance of desired pH during fermentative hydrogen production is regarded as the most important operation parameter for the stable hydrogen production. Therefore, when the potential of hydrogen production from FW and better buffer capacity of WAS, the proper mixture of FW and WAS for fermentative hydrogen production were considered as a useful complementary substrate. The maximum yield of specific hydrogen production, 140 mL/g VSS, was found at HRT of 2 day and the volumetric mixing ratio of 20:80 (WAS : FW). The spatial distribution of hydrogen producing bacteria was observed in anaerobic fermentative reactor using fluorescent in situ hybridization (FISH) method.

• KSBB Journal
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• v.20 no.5 s.94
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• pp.350-354
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• 2005

In order to maximize hydrogen production by Enterobacter cloacae YJ-1, anaerobic hydrogen producing bacteria, the medium composition was optimized. Glucose was better than other carbon sources in hydrogen production and its production was 975.4 mL/L at $2\%$ (w/v) for 48 h. Organic nitrogen sources were more effective than inorganic nitrogen sources and also yeast extract among organic nitrogens was the most effective in hydrogen production. Among metal ions, $Na_2MoO_4$ was most effective, and its production was 1753.3mL/L at $0.04\%$ (w/v). Addition of amino acid was very effective with compare to another components of medium, and cystein was most effective among them. Under the optimum medium obtained in batch culture, semi-batch culture in order to produce continuous hydrogen was run. The highest hydrogen production was earned at $3\%$(w/v) of glucose and the amount was 2215.4 mL/L.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.3
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• pp.376-380
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• 2006

An experiment was conducted to study the effect of temperature and pH on in vitro nutrient degradability, volatile fatty acid profile and methane production. The fermenter used was the semi-continuous system, known as the rumen simulation technique (RUSITEC). Sixteen cylinders were used at one time with a volume of 800 ml, the dilution rate was set at 3.5%/hour, the infused buffer being McDougall's artificial saliva. Basal diet (9.6 g DM) used in RUSITEC consisted of (DM) 6.40 g Timothy hay, 1.86 g crushed corn and 1.34 g soybean meal. The food for the fermentation vessel was provided in nylon bags, which were gently agitated in the liquid phase. The experiment lasted for 17 d with all the samples taken during the last 5 d. Treatments were allocated at random to four vessels each and were (1) two temperature levels of $39^{\circ}C$ and $41^{\circ}C$ (2) two pH levels of 6.0 and 7.0. The total diet contained ($g\;kg^{-1}$ DM) 957 OM, 115 CP and $167MJ\;kg^{-1}$ (DM) GE. Although increase in temperature from $39^{\circ}C$ to $41^{\circ}C$ reduced degradation of major nutrients in vitro, it was non-significant. Interaction effect of temperature with pH also reflected a similar trend. However, pH showed a significant (p<0.05) negative effect on the degradability of all the nutrients in vitro. Altering the in vitro pH from 7 to 6 caused marked reduction in DMD from 60.2 to 41.8, CPD from 76.3 to 55.3 and GED from 55.3 to 35.1, respectively. Low pH (6) depressed total VFA production (61.9 vs. 34.9 mM) as well as acetate to propionate ratio in vitro (from 2.0 to 1.5) when compared to pH 7. Compared to pH 7, total gas production decreased from 1,841 ml to 1,148 ml at pH 6, $CO_2$ and $CH_4$ production also reduced from 639 to 260 ml and 138 to 45 ml, respectively. This study supported the premise that pH is one of the principal factors affecting the microbial production of volatile fatty acids and gas. Regulating the ruminal pH to increase bacterial activity may be one of the methods to optimize VFA production, reduce methane and, possibly, improve animal performance.