• 한국수소및신에너지학회논문집
• /
• 제24권2호
• /
• pp.99-106
• /
• 2013

The variations of performance and metabolites at an early stage were investigated for the successful start-up technology in continuous fermentative hydrogen production. Unsuccessful start-up was observed when the operation mode was changed from batch to continuous mode after the yield was reached to 0.5 mol $H_2$/mol $hexose_{added}$ by batch mode. $H_2$ production continued till 12 hours accompanied by butyrate production, but did not last with propionate production increase. It was suspected that the failure was due to the regrowth of propionic acid bacteria during batch mode which were inhibited by heat-shock but not completely killed. Thus, successful start-up was tried by early switchover from batch to continuous operation; continuous operation was started after the $H_2$ yield was reached to 0.2 mol $H_2$/mol $hexose_{added}$ by batch mode. Although $H_2$ production rate decreased at an early stage, stable $H_2$ yield of 0.8 mol $H_2$/mol $hexose_{added}$ was achieved after 10 days by lowering down propionate production. And it was also concluded that the reason for $H_2$ production decrease at an early stage was due to alcohol production by self detoxification mechanism against VFAs accumulation.

• Journal of Microbiology and Biotechnology
• /
• 제2권4호
• /
• pp.284-287
• /
• 1992

Repeated-batch and continuous cultures of Lactococcus sp. 1112-1 were carried out for bacteriocin production using a glucose-casein medium. Repeated-batch culture did not efficiently enhanced the bacteriocin production. Continuous production was possible at the dilution rate of 0.4 $h^{-1}$. Maximum specific production rate ($Q^p$), bacteriocin production and biomass at the dilution rate were 347, 136 IU/g/h, 2, 121 IU/ml and 2.45 g/L, respectively.

• 한국미생물·생명공학회지
• /
• 제19권1호
• /
• pp.70-75
• /
• 1991

Continuous and simultaneous production of gluconic acid and sorbitol from glucose and fructose was carried out by using glucose-fructose oxidoreductase and glucanolactonase of Zymomonas mobilis. In order to utilize the enzymes without purification, Zymomonas mobilis was permeabilized with toluene. Optimum conditions for permeabilization and reaction kinetics of permeabilized Zymomonas mobilis were studied. In batch operation with the permeabilized cells immobilized in alginate beads, about 90% conversion was obtained within 35 h reaction. Continuous production of gluconic acid and sorbitol using the immobilized permeabilized cells was carried out. Optimum conditions for continuous operation with the imn~obilized cells were; pH 6.2 and temperature $40^{\circ}C$. Maximum productivities for gluconic acid and sorbitol were about 14.5 g/l/h and 14.8 g/l/h respectively at the dilution rate of 0.075 $h^{-1}$ when 300 g/l each of substrates was fed.

• ALGAE
• /
• 제39권2호
• /
• pp.109-127
• /
• 2024

High production and efficient harvesting of microalgae containing high omega-3 levels are critical concerns for industrial use. Aeration can elevate production of some microalgae by providing CO₂ and O₂. However, it may lower the production of others by generating shear stress, causing severe cell damage. The mixotrophic dinoflagellate Gymnodinium smaydae is a new, promising microalga for omega-3 fatty acid production owing to its high docosahexaenoic acid content, and determining optimal conditions and methods for high omega-3 fatty acid production and efficient harvest using G. smaydae is crucial for its commercial utilization. Therefore, to determine whether continuous aeration is required, we measured densities of G. smaydae and the dinoflagellate prey Heterocapsa rotundata in a 100-L semi-continuous cultivation system under no aeration and continuous aeration conditions daily for 9 days. Furthermore, to determine the optimal conditions for harvesting through centrifugation, different rotational speeds of the continuous centrifuge and different flow rates of the pump injecting G. smaydae + H. rotundata cells into the centrifuge were tested. Under continuous aeration, G. smaydae production gradually decreased; however, without aeration, the production remained stable. Harvesting efficiency and the dry weights of omega-3 fatty acids of G. smaydae + H. rotundata cells at a rotational speed of 16,000 rpm were significantly higher than those at 2,000-8,000 rpm. However, these parameters did not significantly differ at injection pump flow rates of 1.0-4.0 L min^-1. The results of the present study provide a basis for optimized production and harvest conditions for G. smaydae and other microalgae.

• 한국습지학회지
• /
• 제9권1호
• /
• pp.123-131
• /
• 2007

Effect of nitrogen-load condition on hydrogen ($H_2$) production and bacterial community in a continuous anaerobic hydrogen fermentation were investigated. The slight $H_2$ production on extremely low nitrogen-load condition (C/N ratio: 180) at the start-up period. The highest $H_2$ production was obtained when the C/N ratio was 36, the $H_2$ production yield ($mol-H_2/mol-glucose$) reached to 1.7, and it was indicated that Clostridium pasteurianum mainly contributed to the $H_2$ production. The $H_2$ production was decreased on both the lower (C/N: 72) and higher (C/N: 18) nitrogen-load conditions. The excess nitrogen-load was not always suitable for the hydrogen production. The fluctuation of $H_2$ production seemed to be caused by a change in the bacterial community according to the nitrogen-load condition, while a recovery of $H_2$ productivity was possible by a control of nitrogen-load condition through the bacterial community change. When the nitrogen-load condition was not suitable for hydrogen production, the lactic acid concentration was increased and also lactic acid bacteria were definitely detected, which suggested that the competition between hydrogen fermentator and lactic acid producer was occurred. These results demonstrated that the nitrogen-load condition affect on the $H_2$ productivity through the change of bacterial community in anaerobic hydrogen fermentation.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
• /
• pp.338-341
• /
• 2000

An internal membrane bioreactor system was employed for continuous succinic ac id production from glucose in order to prove its performance and practicality. Succinic acid-producing Anaerobiospirillum succiniciproducens required more $CO_2$ for the proper growth and succinic acid production in cell recycled continuous culture than in batch culture. The maximum productivity obtained in cell recycled continuous culture was about 3.3 g/L-h which was ca. 3.3 times higher than that obtained in batch culture.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제10권3호
• /
• pp.270-274
• /
• 2005

A reactor-scale hydrogen (H2) production via the water-gas shift reaction of carbon monoxide (CO) and water was studied using the purple nonsulfur bacterium, Rhodopseudomonas palustris P4. The experiment was conducted in a two-step process: an aerobic/chemoheterotrophic cell growth step and a subsequent anaerobic $H_2$ production step. Important parameters investigated included the agitation speed. inlet CO concentration and gas retention time. P4 showed a stable $H_2$ production capability with a maximum activity of 41 mmol $H_2$ g $cell^{-1}h^{-1}$ during the continuous reactor operation of 400 h. The maximal volumetric H2 production rate was estimated to be 41 mmol $H_2 L^{-1}h^{-1}$, which was about nine-fold and fifteen-fold higher than the rates reported for the photosynthetic bacteria Rhodospirillum rubrum and Rubrivivax gelatinosus, respectively. This is mainly attributed to the ability of P4 to grow to a high cell density with a high specific $H_2$ production activity. This study indicates that P4 has an outstanding potential for a continuous H2 production via the water-gas shift reaction once a proper bioreactor system that provides a high rate of gas-liquid mass transfer is developed.

• 생명과학회지
• /
• 제14권1호
• /
• pp.167-173
• /
• 2004

Lactobacillus brevis BH-21의 균체를 고정화하여 column형 reactor를 이용하여 $\gamma$-aminobutyric acid의 연속적 생산을 검토하였다. Lactobacillus brevis BH-21에 의한 $\gamma$-aminobutyric acid 생산조건은 고정화 담체로는 3.0% sodium alginate가 좋았고 직경 2.2 mm의 bead를 사용하여 기질의 주입속도는 10 mL/h이 최적 조건이었다. Lactobacillus brevis BH-21의 고정화 균체와 유리 균체를 사용하여 $\gamma$-aminobutyric acid의 생산을 최적 조건하에서 1, 2, 3, 및 4차 발효 동안 48시간마다 신선한 기질을 주입하면서 비교ㆍ조사한 결과 고정화 균체를 사용 시에 생산량이 더 많았다. Column형 reactor에 의한 연속 발효 시 발효 25일까지 생산이 우수하였고 발효 30일까지는 $\gamma$-aminobutyric acid를 생산할 수 있었다.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제7권2호
• /
• pp.89-94
• /
• 2002

The continuous production of citric acid from dairy wastewater was investigated using calcium-alginate immobilized Asrergillus niger ATCC 9142. The citric acid productivity and yield were strongly affected by the culture conditions. The optimal pH, temperature, and dilution rate were 3.0, 30$^{\circ}C$, and 0.025 h$\^$-1/, respectively. Under optimal culture conditions, the maximum productivity, concentration, and yield of citric acid produced by the calcium-alginate immobilized Aspergillus niger were 160 mg L$\^$-1/ h$\^$-1/, 4.5 g/L, and 70.3%, respectively, The culture was continuously perfored for 20 days without any apparent loss in citric acid productivity. Conversely, under the same conditions with a batch shake-flask culture, the maximum productivity, citric acid concentration, and yield were only 63.3 mg L$\^$-1/h$\^$-1/, 4.7 g/L and 51.4%, respectively, Therefore, the results suggest that the bioreactor used in this study could be potentially used for continuous citric acid production from dairy wastewater by applying calcium-alginate immobilized Aspergillus niger.

• KSBB Journal
• /
• 제5권3호
• /
• pp.223-227
• /
• 1990

Ethanol을 주로 생산하는 균주인 Z. mobilis의 cell wall 투과성을 높인 후 고정화하여 sorbitol 생산에 이용 하였다. 그러나, toluene으로 투과성을 높은 cell은 oxidoreductase의 유출, 손실로 인하여 sorbitol conversion efficency가 급격히 저하되었다. 따라서, 이와같은 enzymcd의 유출을 방지 하기 위하여, 투과성을 향상시킨 cell을 0.25% glutaraldehyd로 처리한 후 alginate와 chitin에 고정화하여 회석율 $0.2h^{-1}$에서 연속배양을 한 결과 210시간동안 효소활성도의 저하는 거의 일어나지 않았다. 이와같은 연속배양에서 얻어진 sorbitol productivity는 3.5g / l-h로 측정 되었다.