• Transactions of the Korean hydrogen and new energy society
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• v.26 no.3
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• pp.247-259
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• 2015

This study was performed to investigate the application of dark $H_2$ fermentation to two-stage bioprocesses for organic waste treatment and energy production. We reviewed information about the two-stage bioprocesses combining dark $H_2$ fermentation with $CH_4$ fermentation, photo $H_2$ fermentation, microbial fuel cells (MFCs), or microbial electrolysis cells (MECs) by using academic information databases and university libraries. Dark fermentative bacteria use organic waste as the sole source of electrons and energy, converting it into $H_2$. The reactions related to dark $H_2$ fermentation are rapid and do not require sunlight, making them useful for treating organic waste. However, the degradation is not complete and organic acids remain. Thus, dark $H_2$ fermentation should be combined with a post-treatment process, such as $CH_4$ fermentation, photo $H_2$ fermentation, MFCs, or MECs. So far, dark $H_2$ fermentation followed by $CH_4$ fermentation is a promising two-stage bioprocess among them. However, if the problems of manufacturing expenses, operational cost, scale-up, and practical applications will be solved, the two-stage bioprocesses combining dark $H_2$ fermentation with photo $H_2$ fermentation, MFCs, or MECs have also infinite potential in organic waste treatment and energy production. This paper demonstrated the feasibility of two-stage bioprocesses combining dark $H_2$ fermentation as a novel system for organic waste treatment and energy production.

• Journal of Microbiology and Biotechnology
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• v.5 no.5
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• pp.292-296
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• 1995

Production of poly($\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate)[poly(HB-co-HV) from glucose and propionic acid was studied in a two-stage fed-batch fermentation using Alcaligenes eutrophus NCIMB 11599. When either glucose became sufficient or the feeding rate of propionic acid decreased, production of poly(HB-co-HV) increased but concomitantly resulted in a reduced fraction of HV. During the copolymer accumulation stage, the specific production rate of hydroxyvalerate (HV) increased up to 0.013 (g-HV/g-RCM/h) but it decreased as propionic acid was accumulated. Control of the propionic acid concentration in the medium, therefore, is considered to be one of the most important operating parameters for production of poly(HB-co-HV) with a higher HV fraction. A high titre of poly(HB-co-HV) (85.6 g/I) with HV fraction of 11.4 mol$%$ could be obtained in 50 h by controlling the propionic acid concentration at 1 to 4 g/I.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.3
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• pp.138-149
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• 2002

Plant cell culture provides a viable alternative over whole plant cultivation for the production of secondary metabolites. In order to successfully cultivate the plant cells at large scale, several engineering parameters such as, cell aggregation, mixing, aeration, and shear sensitivity are taken into account for selection of a suitable bioreactor. The media ingredients, their concentrations and the environmental factors are optimized for maximal synthesis of a desired metabolite. Increased productivity in a bioreactor can be achieved by selection of a proper cultivation strategy (batch, fed-batch, two-stage etc.), feeding of metabolic precursors and extraction of intracellular metabolites. Proper understanding and rigorous analysis of these parameters would pave the way towards the successful commercialization of plant cell bioprocesses.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.5
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• pp.419-422
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• 2004

Textile wastewater from the Pusan Dyeing Industrial Complex (PDIC) was treated utilizing a two-stage continuous system, composed of an upflow anaerobic sludge blanket reactor and an activated Sludge reactor. The effects of color and organic leading rates were studied by varying the hydraulic retention time and influent glucose concentration. The maximum color load to Satisfy the legal discharge limit of color intensity in Korea (400 ADMI, unit of the American Dye Manufacturers Institute) was estimated to be 2,700 $ADMI{\cdot}L^{-1}\;day^{-1}$. This study Indicates that the two-stage anaerobic/aerobic reaction system is potentially useful in the treatment of textile wastewater.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.4
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• pp.313-318
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• 2006

A two-stage process of nanofiltration and water-splitting electrodialysis was investigated for lactic acid recovery from fermentation broth. In this process, sodium lactate is isolated from fermentation broth in the first stage of nanofiltration by using an NTR-729HF membrane, and then is converted to lactic acid in the second stage by water-splitting electrodialysis. To determine the optimal operating conditions for nanofiltration, the effects of pressure, lactate concentration, pH, and known added impurities were studied. Lactate rejection was less than 5%, magnesium rejection approximated 45%, and calcium rejection was at 40%. In subsequent water-splitting electrodialysis, both the sodium lactate conversion to lactic acid and sodium hydroxide recovery, were about 95%, with a power requirement of $0.9{\sim}1.0\; kWh$ per kg of lactate.

• Food Science and Biotechnology
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• v.16 no.6
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• pp.954-957
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• 2007

Gelation mechanism of xanthan-carob mixture (X/C) was investigated based on thermorheological behavior. Three X/C ratios (1:3, 1:1, and 3:1) were studied. Small amplitude oscillatory shear tests were performed to measure linear viscoelastic behavior during gelation. Temperature sweep ($-1^{\circ}C/min$) experiments were conducted. Using a non-isothermal kinetic model, activation energy (Ea) during gelation was calculated. At 1% total concentration, the Ea for xanthan fraction (${\phi}_x$)=0.25, 0.5, and 0.75 were 178, 159, and 123 kJ/mol, respectively. However, a discontinuity was observed in the activation energy plots. Based on this, two gelation mechanisms were presumed-association of xanthan and carob molecules and aggregation of polymer strands. The association process is the primary mechanism to form 3-D networks in the initial stage of gelation and the aggregation of polymer strands played a major role in the later stage.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.5
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• pp.269-278
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• 2003

Gibberellic acid (GA$_3$) is a commercially important plant growth hormone, which is gaining much more attention all over the world due to its effective use in agriculture and brewing industry. Industrially it is produced by submerged fermentation technique using Ascomycetous fungus Gibberella fujikuroi. Solid state and immobilized cell fermentation techniques had also been developed as an alternative to obtain higher yield of GA$_3$. This review summarizes the problems of GA$_3$ fermentation such as production of co-secondary metabolites along with GA$_3$, substrate inhibition and degradation of GA$_3$ to biologically inert compound gibberellenic acid, which limits the yield of GA$_3$ in the fermentation medium. These problems can be overcome by various bioprocessing strategies e.g. two - stage and fed batch cultivation processes. Further research on bioreactor operation strategies such as continuous and / or extractive fermentation with or without cell recycle / retention system need to be investigated for improvement in yield and productivity. Down stream processing for GA$_3$ isolation is also a challenge and procedures available for the same have been critically evaluated.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.425-431
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• 2006

The development of fermentation conditions for the production of C595 diabody fragment (dbFv) in E. coli HB2151 clone has been explored. Investigations were carried out to study the effect of carbon supplements over the expression period, the comparison of C595 dbfv production in synthetic and complex media, the influence of acetic acid upon antibody production, and comparison of one-stage and two-stage processes operated at batch or fed-batch modes in bioreactor. Yeast extract supplied during expression yielded more antibody fragment than any other carbon supply. The synthetic medium presented higher specific productivity (0.066 mg dbFv $g^{-1}$ dry cell weight) when compared to the complex medium (0.044 mg dbFv $g^{-1}$ DCW). The comparison of fermentation strategies demonstrated that (1) one-stage fed-batch fermentation performed higher C595 dbFv production than that operated in batch mode which was significantly affected by acetate concentration; (2) a two-stage batch operation could enhance C595 dbFv production. It was found that a concentration of 12.3 mg $L^{-1}$ broth of C595 dbFv and a cell concentration of 10.8g $L^{-1}$ broth were achieved at the end of two-stage operation in 5-L fermentation.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.2
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• pp.67-75
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• 2002

The human complement receptor type 1 (CR 1, C3 b/C4b receptor) is a polymorphic membrane glycoprotein expressed on human erythrocytes, peripheral leukocytes, plasma and renal glomerular podocytes, which consists of transmembrane and cytoplasmic domains with 30 repeating homologous protein domains known as short consensus repeats (SCR). CR1 has been used as an inhibitor for inflammatory and immune system for the past several years. Recently; it is reported that CRl was found to suppress the hyper-acute rejection in xeno-transplantation and can be used to cure autoimmune diseases. A soluble form of CRl, called sCRl, is a recombinant CRl by cleaving the transmembrane domain at C-terminus and has been expressed in Chinese Hamster Ovary (CHO) cells. Several purification methods for sCR1 from CHO cells have been reported, but most of them require complicated steps at high cost. Moreover, such methods are mostly performed under the pH condition apt to denaturing sCR1 and causes sCRl losing its activity. We here report a rapid and efficient method to purify sCR1 from CHO cell. The new method consists of a two-stage of cell culture by cultivating cells in serum medium followed by serum-free medium, and a two-stage of column purification by means of heparin and gel filtration column chromatography. By using this novel method, sCR1 can be purified in a simple and effective way with high yield and purity, furthermore, the purified sCR1 was confirmed to retain its activity to suppress the complement activation in vivo and ex vivo.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.6
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• pp.322-330
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• 2003

The unicellular green alga Haematococcus pluvialis has recently attracted great inter-est due to its large amounts of ketocarotenoid astaxanthin, 3,3'-dihydroxy-${\beta}$,${\beta}$-carotene-4,4'-dione, widely used commercially as a source of pigment for aquaculture. In the life cycle of H. pluvialis, astaxanthin biosynthesis is associated with a remarkable morphological change from green motile vegetative cells into red immotile cyst cells as the resting stage. In recent years we have studied this morphological process from two aspects: defining conditions governing astaxanthin biosynthesis and questioning the possible function of astaxanthin in protecting algal cells against environmental stress. Astaxanthin accumulation in cysts was induced by a variety of environmental conditions of oxidative stress caused by reactive oxygen species, intense light, drought, high salinity, and high temperature. In the adaptation to stress, abscisic acid induced by reactive oxygen species, would function as a hormone in algal morphogenesis from veget ative to cyst cells. Furthermore, measurements of both in vitro and in vivo antioxidative activities of astaxanthin clearly demonstrated that tolerance to excessive reactive oxygen species is greater in astaxanthin-rich cysts than in astaxanthin-poor cysts or astaxanthin-less vegetative cells. Therefore, reactive oxygen species are involved in the regulation of both algal morph O-genesis and carotenogenesis, and the accumulated astaxanthin in cysts can function as a protective agent against oxidative stress damage. In this study, the physiological roles of astaxanthin in stress response and cell protection are reviewed.