• Journal of Animal Science and Technology
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• v.62 no.1
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• pp.1-13
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• 2020

This study was designed to evaluate the in vitro and in vivo effects of reductive acetogens isolated from ruminants on methane mitigation, and milk performance, respectively. Four acetogens, Proteiniphilum acetatigenes DA02, P. acetatigenes GA01, Alkaliphilus crotonatoxidans GA02, and P. acetatigenes GA03 strains were isolated from ruminants and used in in vitro experiment. A control (without acetogen) and a positive group (with Eubacterium limosum ATCC 8486) were also included in in vitro experiment. Based on higher acetate as well as lower methane producing ability in in vitro trial, P. acetatigenes GA03 was used as inoculum for in vivo experiment. Holstein dairy cows (n = 14) were divided into two groups viz. control (without) and GA03 group (diet supplied with P. acetatigenes GA03 at a feed rate of 1% supplementation). Milk performance and blood parameters were checked for both groups. In in vitro, the total volatile fatty acids and acetate production were higher (p < 0.05) in all 4 isolated acetogens than the control and positive treatment. Also, all acetogens significantly lowered (p < 0.05) methane production in comparison to positive and control groups however, GA03 had the lowest (p < 0.05) methane production among 4 isolates. In in vivo, the rate of milk yield reduction was higher (p < 0.05) in the control than GA03 treated group (5.07 vs 2.4 kg). Similarly, the decrease in milk fat was also higher in control (0.14% vs 0.09%) than treatment. The somatic cell counts (SCC; ×10³/mL) was decreased from 128.43 to 107.00 in acetogen treated group however, increased in control from 138.14 to 395.71. In addition, GA03 increased blood glucose and decreased non-esterified fatty acids. Our results suggest that the isolated acetogens have the potential for in vitro methane reduction and P. acetatigenes GA03 strain could be a candidate probiotic strain for improving milk yield and milk fat in lactating cows with lowering SCCs.

• Microbiology and Biotechnology Letters
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• v.25 no.1
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• pp.1-8
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• 1997

Carbon monoxide (CO)-utilizing acetogens were enriched and KIST612 isolated from anaerobic digester fluid was selected for its abilities to tolerate high CO and acetate concentration. The isolate KIST612 was identified as Eubacterium limosum based on the morphological and biochemical characteristics, G+C content of DNA and 16S rRNA sequence analysis. E. limosum KIST612 produced acetate and butyrate from CO. The optimum temperature and pH for the growth and acids formations were 37$\cdot $C and 7.0, respectively. The growth rate and acids productivity of E. limosum KIST612 were higher than those of any other known acetogens when CO was used as the sole energy and carbon source.

• Journal of Microbiology and Biotechnology
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• v.22 no.5
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• pp.668-673
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• 2012

Biohydrogen production from organic wastewater by anaerobically activated sludge fermentation has already been extensively investigated, and it is known that hydrogen can be produced by glucose fermentation through three metabolic pathways, including the oxidative decarboxylation of pyruvic acid to acetyl-CoA, oxidation of NADH to $NAD^+$, and acetogenesis by hydrogen-producing acetogens. However, the exact or dominant pathways of hydrogen production in the anaerobically activated sludge fermentation process have not yet been identified. Thus, a continuous stirred-tank reactor (CSTR) was introduced and a specifically acclimated acidogenic fermentative microflora obtained under certain operation conditions. The hydrogen production activity and potential hydrogen-producing pathways in the acidogenic fermentative microflora were then investigated using batch cultures in Erlenmeyer flasks with a working volume of 500 ml. Based on an initial glucose concentration of 10 g/l, pH 6.0, and a biomass of 1.01 g/l of a mixed liquid volatile suspended solid (MLVSS), 247.7 ml of hydrogen was obtained after a 68 h cultivation period at $35{\pm}1^{\circ}C$. Further tests indicated that 69% of the hydrogen was produced from the oxidative decarboxylation of pyruvic acid, whereas the remaining 31% was from the oxidation of NADH to $NAD^+$. There were no hydrogen-producing acetogens or they were unable to work effectively in the anaerobically activated sludge with a hydraulic retention time (HRT) of less than 8 h.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.993-997
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• 2007

The upflow anaerobic sludge blanket (UASB) reactor can be effective for treating simple organic compounds containing high concentration of ammonia nitrogen. The chemical oxygen demand (COD) removal efficiency was about 80% at ammonia nitrogen concentration up to 6,000 mg-N/L. This result also showed that it would be possible to treat propionate effectively at free ammonia nitrogen concentration up to 724 mg-N/L if sufficient time was allowed for adaptation. However the specific methanogenic activity (SMA) of granule was lower than that of granule in the reactor with lower ammonia nitrogen concentration. At 8,000 mg-N/L, the inhibition of high ammonia concentration was observed with evidence of increase of the volatile suspended solids (VSS) concentration in the effluent. It might be ascribed to the decrease in the content of extracellular polymer (ECP), which resulted to the sloughing off of obligated proton-reducing acetogens and heterogenotrophic methanogens from the exterior of granular sludge. This caused a great portion of the finely sludge to be easily washed out. Therefore, failure to maintain the balance between these two groups of microorganism cause accumulation of the hydrogen partial pressure in the reactor, which could have inhibited the growth of acetate utilizing methanogens.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.2
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• pp.1-6
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• 2009

Acetogen과 같은 일부 혐기성미생물은 소위 acetyl-CoA 경로에 의해 아세트산, 에탄올, 그리고 몇 가지 생화학 물질을 생산한다. 이 경로에서는 일산화탄소를 기질로 이용할 수 있다. 일산화탄소 이외에 수소가 이용될 수 있다. 즉 이들 미생물은 독립영양생물로서 이산화탄소와 태양광에너지를 이용하는 녹색식물과 비유될 수 있으며, 일산화탄소는 탄소원으로서 동시에 에너지원으로서 이용된다. 본 연구에서는 혐기성 소화액 중 아세트산을 생성하는 미생물이 존재한다고 가정하고, 일산화탄소와 수소가 주 가연성분인 합성가스를 공급하면 추가의 메탄이 생성가능성을 평가하였다. 혐기성 소화과정에서 발생되는 메탄은 주로 아세트산으로부터 만들어지므로 일산화탄소를 공급하는 경우 추가로 메탄이 생성될 것으로 추측할 수 있기 때문이다. 이를 확인하기 위하여 현재 운영중인 바이오가스 생산 설비로부터 얻은 혐기성 소화액을 생물반응조에 넣은 후, 합성가스를 순환-공급하여 가스 생산량의 변화 및 조성을 분석하였다. 질소가스를 공급한 대조구와는 달리 일산화탄소 또는 합성가스를 공급한 경우에는 메탄가스가 생산되는 것을 확인하였다. 질소가스를 공급한 대조구와는 달리 일산화탄소 또는 합성가스를 공급한 경우에는 메탄가스가 생산되는 것을 확인하였다. 일산화탄소만을 공급했을 때에는 이산화탄소의 생성으로 가스 생산량이 증가하였으나, 수소가 포함된 합성가스를 공급하였을 때에는 이산화탄소가 탄소원이로 소비되어 가스 저장도 내의 가스량이 감소하는 것을 확인할 수 있었다. 가스화공정에 으해 얻어지는 합성가스는 온도와 가스 조성을 고러할 때, 바이오가스 생산을 위한 혐기성 소화조와 연계하면 소화조의 가온에 필요한 열을 공급할 수 있고 바이오가스 중 이산화탄소 농도를 낮추어 발열량을 개선할 수 있을 것으로 판단된다.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.3
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• pp.126-137
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• 2006

Behaviors of simple organic compound and granular sludge in an upflow anaerobic sludge blanket (UASB) reactor treating propionate at high ammonia nitrogen levels were investigated for 12 months. The UASB reactor achieved about 80% removal of chemical oxygen demand (COD) at ammonia nitrogen concentration up to 6000 mg-N/L. At higher concentration of ammonia nitrogen, the propionate in the effluent increased whereas the acetate was very low. At ammonia nitrogen concentration of 8000 mg-N/L, the volatile suspended solids (VSS) increased sharply due probably to the decrease of the content of extracellular polymer (ECP) although methane production was very low. The specific methanogenic activity (SMA) using formate, acetate, and propionate as substrate to granules decreased as ammonia nitrogen concentration increased. The ammonia nitrogen concentration $I^{50}$, causing 50% inhibition of SMA were 2666, 4778 and 5572 mg-N/L, respectively. The kinetic coefficients of ammonia inhibition using formate, acetate, and propionate as substrate were 3.279, 0.999 and 0.609, respectively. The SMA using formate was severely affected by ammonia nitrogen than those using acetate and propionate. This result indicated that the hydrogenotrophic methanogens was most affected by ammonia nitrogen. Granules were mainly composed of microcolonies of methanothrix-like bacteria resembling bamboo-shape, and several other microcolonies including propionate degrader with juxtapositioned syntrophic associations between the hydrogen-producing acetogens and hydrogen-consuming methanogens.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.157-165
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• 2016

Under flooded rice fields, methanogens produce methane which comes out through rice stalks, thus rice fields are known as one of the anthropogenic sources of atmospheric methane. Studies have shown that use of manure increases amount of methane emission from rice. To investigate mechanisms by which manure boosts methane emission, comparative soil metagenomics between inorganically (NPK) and pig manure fertilized paddy soils (PIG) were conducted. Results from taxonomy analysis showed that more abundant methanogens, methanotrophs, methylotrophs, and acetogens were found in PIG than in NPK. In addition, BLAST results indicated more abundant carbohydrate mabolisetm functional genes in PIG. Among the methane metabolism related genes, PIG sample showed higher abundance of methyl-coenzyme M reductase (mcrB/mcrD/mcrG) and trimethylamine-corrinoid protein Co-methyltransferase (mttB) genes. In contrast, genes that down regulate methane emission, such as trimethylamine monooxygenase (tmm) and phosphoserine/homoserine phosphotransferase (thrH), were observed more in NPK sample. In addition, more methanotrophic genes (pmoB/amoB/mxaJ), were found more abundant in PIG sample. Identifying key genes related to methane emission and methane oxidation may provide fundamental information regarding to mechanisms by which use of manure boosts methane emission from rice. The study presented here characterized molecular variation in rice paddy, introduced by the use of pig manure.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.1
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• pp.49-57
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• 2004

The effect of gas sparging on continuous fermentative $H_2$ production was investigated using external gases ($N_2$, $CO_2$) with various flow rates (100, 200, 300, 400 ml/min). Gas sparging showed a higher $H_2$ yield than no sparging, indicating that the decrease of $H_2$ partial pressure by gas sparging had a good effect on $H_2$ fermentation. Especially, $CO_2$ sparging was more effective in the reactor performance than $N_2$ sparging. The composition of butyrate, the main metabolic product of $H_2$ fermentation by Clostridium sp., was much higher in $CO_2$ sparging. $H_2$ production increased with increasing flow rate only in $CO_2$ sparging. The best performance was obtained by $CO_2$ sparging at 300 ml/min, resulting in the highest $H_2$ yield of 1.65 mol $H_2/mol$ hexoseconsumed and the maximum $H_2$ production of 6.77 L $H_2/g$ VSS/day. Compared to $N_2$ sparging, there could be another beneficial effect in $CO_2$ sparging apart from lowering down the $H_2$ partial pressure. High partial pressure of $CO_2$ had little effect on $H_2$ producing bacteria but inhibitory effect on other microorganisms like lactic acid bacteria and acetogens which were competitive with $H_2$ producing bacteria.