• Journal of Hydrogen and New Energy
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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.

• Microbiology and Biotechnology Letters
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• v.20 no.6
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• pp.663-667
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• 1992

The production of vinegar containing 16.0-18.0% of acetic acid was examined in two stage fermentation consisting of semi-continuous and fed-batch type. The optimum conditions were obtained when the fermentation was carried out at agitation of 600 rpm, aeration of 0.1 vvm and temperature of $30^{\circ}C$. The initial and residual ethanol concentration in 1st stage were $50.0g/{\ell}$ and $5.0g/{\ell}$, respectively, and the ethanol concentration in 2nd stage was maintained from 5.0 to $10.0g/{\ell}$. The maximum productivity was 3.3 gll-hr and the acidity was 17.6% after the two days of acetic acid fermentation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.2
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• pp.353-358
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• 1999

We produced the apple vinegar with only apple fruits, no adding sugar and others through two stages fermentation(alcohol fermentation and acetic acid fermentation). At the first stage, apple wine contained 5% alcohol was produced at the 5th day. And through the second stage, acetic acid fer mentation, apple vinegars of which total acidity is 5.88% were produced. In comparision with com mercial vinegars for physicochemical quality, it was the lowest in total acidity. But contents of oxalic, tartaric, malic, citric, succinic acid in it were higher than other vinegars. Especially the content of malic acid in it was higher 5 times than other vinegars. Malic acid was known that it was abundant in apple fruits. Also the contents of free amino acids were distinctly high such as 21.97mg% in two stages fermented apple vingars. Potassium content in it was higher 4 times than other vinegars. So it was supposed that two stages fermented vinegar had much higher quality than commercial vinegars.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.3
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• pp.426-431
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• 2001

We made the Toha-jeot added cabbage kimchi with Toha-jeot, which is salt-fermented Toha shrimp in Korean traditional fermented food. The physicochemical characteristics of cabbage kimchi for 5 week fermentation at 4$^{\circ}C$ were observed. The salt content was 2.10~1.50% during the fermentation period. The salt content decreased rapidly during the first week, stayed the same level until the 4 week and then decreased after the 4 week. The pH of control kimchi and Toha-jeot added cabbage kimchi were 5.69, 5,64, respectively on preparation day. The rate of decrease of pH of Toha-jeot added cabbage kimchi was slow as the fermentation processed. The total acidity of the two kinds of kimchi was increased. The total acidity was higher from Toha-jeot added cabbage kimchi than control cabbage kimchi at the later stage of fermentation. The contents of total sugar and reducing sugar were higher from Toha-jeot added cabbage kimchi than control cabbage kimchi at the early stage of fermentation. The total sugar and reducing sugar contents of the two kinds of cabbage kimchi were decreased gradually as the fermentation processed. The ascorbic acid contents of the two kinds of kimchi were decreased slightly at the early stage of fermentation and then increased from 2 to 4 week, while there was no further change at 5 week.

• Journal of the East Asian Society of Dietary Life
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• v.8 no.1
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• pp.57-65
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• 1998

To utilize deteriorated sweet persimmon effectively, response surface methodology(RSM) was used to determine the optimal vinegar fermentation conditions and monitored by a divided two stage fermentation. The optimum conditions for maximum alcohol content were obtained when the first stage (alcohol fermentation) was carried out with an initial sugar concentration of 18.5$^{\circ}$Brix, agitation rate of 140.8 rpm, fermentation time of 127.6 hr. When sugar concentration was 14$^{\circ}$Brix maximum alcohol content(7.1%) was predicted at fermentation conditions of 160 rpm in agitation rate, 140hr in fermentation time. The optimum conditions for maximum acidity were obtaiend when second stage(vinegar fermentation)was carried out 249.5 rpm in agitation rate, 148.8 hr in fermentation time. Predicted values at the optimum conditions were similar to experimental values.

• Korean Journal of Food Science and Technology
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• v.47 no.4
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• pp.431-437
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• 2015

In this study, high-acidity cider vinegar (HACV) was produced by alcoholic and acetic acid fermentation of apple concentrate without any nutrients and then the optimum alcohol concentration was determined through a qualitative study. HACV was fermented with different initial alcohol concentrations (6-9%) during the process of acetic acid fermentation. The highest content of reducing sugar, organic acids, and free amino acids was observed at 6% of initial alcohol concentration. Approximately 20 types of volatile compounds were identified by solid-phase microextraction (SPME) and GC-MS. The total volatile content was the highest at 6% of initial alcohol concentration, and the acid content was the lowest at 9% of the initial alcohol concentration. The HACV produced by a two-stage fermentation process was qualitatively better than commercial HACV presenting the highest value at 6% of initial alcohol concentration. Malic acid, aspartic acid, and hexyl acetate were selected as quality index components of HACV production by two-stage fermentation on the basis of correlation between their physicochemical properties and the sensory attributes of HACV.

• Journal of Hydrogen and New Energy
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• v.16 no.4
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• pp.315-323
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• 2005

The integrated or the two-stage (dark anaerobic and photosynthetic) fermentation processes were compared for the hydrogen production using purple non-sulfur photosynthetic bacteria, Rhodopseudomonas palustris P4. Cell growth, pH changes and organic acids and bacteriochlorophyll contents were monitored during the processes. Culture broth of Rps. palustris P4 exhibited dark-red during the photosynthetic culture condition, while yellow under the anaerobic condition without light. Rps. palustris P4 grown at the photosynthetic condition evolved 0.38 and 1.33 ml $H_2$/mg-dcw during the dark and the light fermentation, respectively, which were totally 1.71 ml $H_2$/mg-dcw at the two-stage fermentation. The rate of hydrogen production using Rps. palustris P4 grown under the dark anaerobic condition was 2.76 ml $H_2$/mg-dcw which consisted of 0.46 and 2.30 ml $H_2$/mg-dcw from the dark and the photosynthetic fermentation processes, respectively. Rps. palustris P4 grown under dark anaerobic conditions produced $H_2$ 1.6 times higher than that of grown under the photosynthetic condition. However, total fermentation period of the former was 1.5 times slower than that of the latter, because the induced time of hydrogen production during the photosynthetic fermentation was 96 and 24 hours when the seed culture was the dark anaerobic and photosynthetic, respectively. The integrated fermentation process by Rps. palustris P4 produced 0.52 ml $H_2$/mg-dcw(1.01 mol $H_2$/mol glucose), which was 20% of the two-stage fermentation.

• 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.

• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• Journal of Hydrogen and New Energy
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• v.22 no.3
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• pp.333-339
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• 2011

In the present work, it was attempted to produce $H_2$ from food waste by the two-stage fermentation system. Food waste was acidified to lactate by using indigenous lactic acid bacteria under mesophilic condition, and the lactate fermentation effluent (LFE) was subsequently converted to $H_2$ by photo-fermentation. $Rhodobacter$ $sphaeroides$ KD131 was used as the photo-fermenting bacteria. The optimal conditions for lactate fermentation were found to be pH of 5.5 and substrate concentration of 30 g Carbo. COD/L, under which yielded 1.6 mol lactate/mol glucose. By filtering the LFE and adding trace metal, $H_2$ production increased by more than three times compared to using raw LFE, and finally reached the $H_2$ yield of 3.6 mol $H_2$/mol lactate. Via the developed two-stage fermentation system $H_2$ yield of 5.8 mol $H_2$/mol glucose was achieved from food waste, whose value was the highest that ever recorded.