The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Jian Chen - One of the best experts on this subject based on the ideXlab platform.
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an optimal glucose feeding strategy integrated with step wise regulation of the Dissolved Oxygen Level improves n acetylglucosamine production in recombinant bacillus subtilis
Bioresource Technology, 2015Co-Authors: Yanqiu Zhu, Long Liu, Yanfeng Liu, Hyundong Shin, Jian ChenAbstract:Abstract In our previous work, a recombinant Bacillus subtilis strain for the microbial production of N -acetylglucosamine (GlcNAc) was constructed through modular pathway engineering. In this study, to enhance GlcNAc production, glucose feeding approaches and Dissolved Oxygen (DO) control methods in fed-batch culture were systematically investigated. We first studied the effects of different glucose feeding strategies, including exponential fed-batch culture, pulse fed-batch culture, constant rate fed-batch culture, and glucose control (5 g/L, 10 g/L, 15 g/L) fed-batch culture, on cell growth and GlcNAc synthesis. We found that GlcNAc production in glucose control (5 g/L) fed-batch culture reached 26.58 g/L, which was 3.10 times that in batch culture. Next, the effect of DO Level (20%, 30%, 40%, and 50%) on GlcNAc production was investigated, and a step-wise DO control strategy (0–7 h, 30%; 7–15 h, 50%; 15–50 h, 40%; 50–72 h, 30%) was introduced. With the optimal glucose and DO control strategy, GlcNAc production reached 35.77 g/L, which was 4.17 times the production in batch culture without DO control.
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enhanced glucosamine production by aspergillus sp bcrc 31742 based on the time variant kinetics analysis of Dissolved Oxygen Level
Bioresource Technology, 2012Co-Authors: Jiaxin Zhang, Long Liu, Jian ChenAbstract:Abstract This work aims to enhance the glucosamine production by Aspergillus sp. BCRC 31742 via the optimization of Dissolved Oxygen (DO) control strategy. Influence of DO Levels (20, 30, 40, 50 and 60%) on the glucosamine production was investigated, and it was found that the highest specific glucosamine production rate during 0–12 h and 12–60 h was obtained at DO Level of 30% and 50%, respectively. Accordingly, a two-stage DO control strategy was proposed, namely, DO was controlled at 30% during 0–12 h and 50% during 12–60 h. With this DO shifting strategy, the highest glucosamine production reached 14.37 g/L, which was 1.30 times that without DO control. Here, the developed two-stage DO control strategy may be useful for the industrial production of glucosamine, and also may be meaningful for the production of other fine chemicals by the filamentous fungi fermentation.
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improved glucosamine and n acetylglucosamine production by an engineered escherichia coli via step wise regulation of Dissolved Oxygen Level
Bioresource Technology, 2012Co-Authors: Xin Chen, Long Liu, Jian ChenAbstract:Abstract Influence of Dissolved Oxygen (DO) Levels (10%, 20%, 30% and 40%) on the glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) production by recombinant Escherichia coli was investigated. It was found that the highest specific GlcN and GlcNAc production rates were obtained at different DO Levels at different culture stages. Namely, the highest specific GlcN and GlcNAc production rates were obtained at 20% during 0–2 h, 30% during 2–8 h, 40% during 8–12 h, and 30% during 12–18 h. Accordingly, a step-wise DO control strategy was proposed, namely DO was controlled at 20% during 0–2 h, 30% during 2–8 h, 40% during 8–12 h and 30% during 12–18 h. With this DO control approach, the total production of GlcN and GlcNAc reached 72.89 g L−1, which was 1.37 times that without DO control (53.31 g L−1). The developed step-wise DO control strategy may be useful for the industrial GlcN and GlcNAc production by recombinant E. coli.
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Enhanced Hyaluronic Acid Production of Streptococcus zooepidemicus by Shifting Dissolved Oxygen Level Based on Broth Rheology and Oxygen Mass Transfer Characteristics
Food Biotechnology, 2009Co-Authors: Long Liu, Jian Chen, Haiquan Yang, Miao WangAbstract:This research focused on a Dissolved Oxygen (DO)-shifting strategy to enhance the production of hyaluronic acid (HA) by Streptococcus zooepidemicus. In this strategy, DO was controlled at above 10 ± 1% during 0–8 h and at 5 ± 0.5% during 8–18 h. The DO-shifting strategy increased the consistency index and Oxygen mass transfer coefficient and decreased the flow behavior index n. With the proposed DO-shifting strategy, HA production increased from 5.0 ± 0.1 g/L to 6.3 ± 0.1 g/L. The enhanced HA production was attributed to the alleviation of carbon and energy competition between cell growth and HA synthesis.
Hong-wei Yen - One of the best experts on this subject based on the ideXlab platform.
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the synergistic effects for the co cultivation of oleaginous yeast rhodotorula glutinis and microalgae scenedesmus obliquus on the biomass and total lipids accumulation
Bioresource Technology, 2015Co-Authors: Hong-wei Yen, Pinwen Chen, Lijuan ChenAbstract:In this co-culture of oleaginous yeast-Rhodotorula glutinis and microalgae-Scenedesmus obliquus, microalgae potentially acts as an Oxygen generator for the growth of aerobic yeast while the yeast mutually provides CO2 to the microalgae as both carry out the production of lipids. To explore the synergistic effects of co-cultivation on the cells growth and total lipids accumulation, several co-culture process parameters including the carbon source concentration, temperature and Dissolved Oxygen Level would be firstly investigated in the flask trials. The results of co-culture in a 5L photobioreactor revealed that about 40–50% of biomass increased and 60–70% of total lipid increased was observed as compared to the single culture batches. Besides the synergistic effects of gas utilization, the providing of trace elements to each other after the natural cells lysis was believed to be another benefit to the growth of the overall co-culture system.
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The effects of Dissolved Oxygen Level on the distribution of 1,3-propanediol and 2,3-butanediol produced from glycerol by an isolated indigenous Klebsiella sp. Ana-WS5.
Bioresource technology, 2013Co-Authors: Hong-wei Yen, Jo Shu ChangAbstract:The rapid accumulation of glycerol during biodiesel synthesis has attracted much interest on the potential usage. One of the promising applications is the conversion of glycerol to 1,3-propanediol (PDO), as well 2,3-butanediol (BDO), by using Klebsiella pneumonia. The results of this study indicate that the Dissolved Oxygen Level (DO) is a determining factor in the distribution of PDO and BDO. The batch with a low DO could achieve a much higher PDO/BDO ratio than the high DO batch, with results of 9.9 and 0.2, respectively. The enzyme activity of glycerol dehydratase (GDHt) in the low DO batch was about three times that of the high DO batch, and this might be the cause of the enhanced PDO production. In conclusion, the results of this work show that high DO was beneficial to the production of BDO when using glycerol as the carbon source, while low DO could enhance PDO production.
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effects of Dissolved Oxygen Level on rapamycin production by pellet form of streptomyces hygroscopicus
Journal of Bioscience and Bioengineering, 2013Co-Authors: Hong-wei Yen, Hsinpei HsiaoAbstract:Rapamycin was known to have the functions of being an antibiotic and immunosuppressant; recently it was also recognized as being able to retard the aging process. The effects of Dissolved Oxygen (DO) Level on rapamycin production by pellet-form of Streptomyces hygroscopicus were investigated in this study. The results suggest that a high DO Level is required to enhance rapamycin production. However, the premise for getting a high rapamycin concentration by using DO control was keeping the intact of pellet-form of S. hygroscopicus. What if the high DO Level achieved was coming from the increase of agitation; it might break down the morphology of pellets-form in the fermentation tank and result in the decrease of rapamycin production. The maximum rapamycin obtained in this study was about 780 mg/L in the 5 L fermentor batch with DO controlled over 30%, with the supplement of pure Oxygen in the inlet gas, and the agitation speed limited to less than 200 rpm. Conclusively, a high DO Level and the morphology of pellets form both were detrimental to achieving a high rapamycin production by S. hygroscopicus in the agitation fermentor.
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effects of Dissolved Oxygen Level on cell growth and total lipid accumulation in the cultivation of rhodotorula glutinis
Journal of Bioscience and Bioengineering, 2011Co-Authors: Hong-wei Yen, Zhiyong ZhangAbstract:The total amount of lipids produced in Rhodotorula glutinis is a subject which has attracted increasing attention due to the potential biodiesel conversion from these microbial oils. The effects of the Dissolved Oxygen (DO) Level in lipid accumulation were examined in this study. Variations of different medium volumes (30, 40 and 50ml) and shaking speed (60, 150 and 210rpm) in the flask trials were adopted to explore the DO effects on lipid production. All of the results revealed that a low DO could retard cell growth, while enhancing lipid accumulation. The 5l-fermentor results also confirm that a low DO (25 ± 10%) batch could have higher lipid content than that of high DO batch (60 ± 10%). Nevertheless, the DO Level would not obviously affect the lipid composition profile. Oleic acid (C18:1) was the primary fatty acid in both batches. Due to the slow biomass growth rate resulting from the low DO, a two-stage DO controlled strategy (consisting of a high DO stage and following a low DO stage) was performed to improve the cell growth and lipid accumulation simultaneously. However, the strategy was not successful on the enhancement of total lipid production as compared to other batches. Conclusively, even a low DO could retard cell growth; the total production of lipids in the batch with low DO was higher that of the high DO batch due to the enhancement of lipid accumulation. Therefore, the batch operation of R. glutinis at the low DO was suggested for the purpose of lipid production.
Long Liu - One of the best experts on this subject based on the ideXlab platform.
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an optimal glucose feeding strategy integrated with step wise regulation of the Dissolved Oxygen Level improves n acetylglucosamine production in recombinant bacillus subtilis
Bioresource Technology, 2015Co-Authors: Yanqiu Zhu, Long Liu, Yanfeng Liu, Hyundong Shin, Jian ChenAbstract:Abstract In our previous work, a recombinant Bacillus subtilis strain for the microbial production of N -acetylglucosamine (GlcNAc) was constructed through modular pathway engineering. In this study, to enhance GlcNAc production, glucose feeding approaches and Dissolved Oxygen (DO) control methods in fed-batch culture were systematically investigated. We first studied the effects of different glucose feeding strategies, including exponential fed-batch culture, pulse fed-batch culture, constant rate fed-batch culture, and glucose control (5 g/L, 10 g/L, 15 g/L) fed-batch culture, on cell growth and GlcNAc synthesis. We found that GlcNAc production in glucose control (5 g/L) fed-batch culture reached 26.58 g/L, which was 3.10 times that in batch culture. Next, the effect of DO Level (20%, 30%, 40%, and 50%) on GlcNAc production was investigated, and a step-wise DO control strategy (0–7 h, 30%; 7–15 h, 50%; 15–50 h, 40%; 50–72 h, 30%) was introduced. With the optimal glucose and DO control strategy, GlcNAc production reached 35.77 g/L, which was 4.17 times the production in batch culture without DO control.
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enhanced glucosamine production by aspergillus sp bcrc 31742 based on the time variant kinetics analysis of Dissolved Oxygen Level
Bioresource Technology, 2012Co-Authors: Jiaxin Zhang, Long Liu, Jian ChenAbstract:Abstract This work aims to enhance the glucosamine production by Aspergillus sp. BCRC 31742 via the optimization of Dissolved Oxygen (DO) control strategy. Influence of DO Levels (20, 30, 40, 50 and 60%) on the glucosamine production was investigated, and it was found that the highest specific glucosamine production rate during 0–12 h and 12–60 h was obtained at DO Level of 30% and 50%, respectively. Accordingly, a two-stage DO control strategy was proposed, namely, DO was controlled at 30% during 0–12 h and 50% during 12–60 h. With this DO shifting strategy, the highest glucosamine production reached 14.37 g/L, which was 1.30 times that without DO control. Here, the developed two-stage DO control strategy may be useful for the industrial production of glucosamine, and also may be meaningful for the production of other fine chemicals by the filamentous fungi fermentation.
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improved glucosamine and n acetylglucosamine production by an engineered escherichia coli via step wise regulation of Dissolved Oxygen Level
Bioresource Technology, 2012Co-Authors: Xin Chen, Long Liu, Jian ChenAbstract:Abstract Influence of Dissolved Oxygen (DO) Levels (10%, 20%, 30% and 40%) on the glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) production by recombinant Escherichia coli was investigated. It was found that the highest specific GlcN and GlcNAc production rates were obtained at different DO Levels at different culture stages. Namely, the highest specific GlcN and GlcNAc production rates were obtained at 20% during 0–2 h, 30% during 2–8 h, 40% during 8–12 h, and 30% during 12–18 h. Accordingly, a step-wise DO control strategy was proposed, namely DO was controlled at 20% during 0–2 h, 30% during 2–8 h, 40% during 8–12 h and 30% during 12–18 h. With this DO control approach, the total production of GlcN and GlcNAc reached 72.89 g L−1, which was 1.37 times that without DO control (53.31 g L−1). The developed step-wise DO control strategy may be useful for the industrial GlcN and GlcNAc production by recombinant E. coli.
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Enhanced Hyaluronic Acid Production of Streptococcus zooepidemicus by Shifting Dissolved Oxygen Level Based on Broth Rheology and Oxygen Mass Transfer Characteristics
Food Biotechnology, 2009Co-Authors: Long Liu, Jian Chen, Haiquan Yang, Miao WangAbstract:This research focused on a Dissolved Oxygen (DO)-shifting strategy to enhance the production of hyaluronic acid (HA) by Streptococcus zooepidemicus. In this strategy, DO was controlled at above 10 ± 1% during 0–8 h and at 5 ± 0.5% during 8–18 h. The DO-shifting strategy increased the consistency index and Oxygen mass transfer coefficient and decreased the flow behavior index n. With the proposed DO-shifting strategy, HA production increased from 5.0 ± 0.1 g/L to 6.3 ± 0.1 g/L. The enhanced HA production was attributed to the alleviation of carbon and energy competition between cell growth and HA synthesis.
Zhiyong Zhang - One of the best experts on this subject based on the ideXlab platform.
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effects of Dissolved Oxygen Level on cell growth and total lipid accumulation in the cultivation of rhodotorula glutinis
Journal of Bioscience and Bioengineering, 2011Co-Authors: Hong-wei Yen, Zhiyong ZhangAbstract:The total amount of lipids produced in Rhodotorula glutinis is a subject which has attracted increasing attention due to the potential biodiesel conversion from these microbial oils. The effects of the Dissolved Oxygen (DO) Level in lipid accumulation were examined in this study. Variations of different medium volumes (30, 40 and 50ml) and shaking speed (60, 150 and 210rpm) in the flask trials were adopted to explore the DO effects on lipid production. All of the results revealed that a low DO could retard cell growth, while enhancing lipid accumulation. The 5l-fermentor results also confirm that a low DO (25 ± 10%) batch could have higher lipid content than that of high DO batch (60 ± 10%). Nevertheless, the DO Level would not obviously affect the lipid composition profile. Oleic acid (C18:1) was the primary fatty acid in both batches. Due to the slow biomass growth rate resulting from the low DO, a two-stage DO controlled strategy (consisting of a high DO stage and following a low DO stage) was performed to improve the cell growth and lipid accumulation simultaneously. However, the strategy was not successful on the enhancement of total lipid production as compared to other batches. Conclusively, even a low DO could retard cell growth; the total production of lipids in the batch with low DO was higher that of the high DO batch due to the enhancement of lipid accumulation. Therefore, the batch operation of R. glutinis at the low DO was suggested for the purpose of lipid production.
Shulin Chen - One of the best experts on this subject based on the ideXlab platform.
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study of a two stage growth of dha producing marine algae schizochytrium limacinum sr21 with shifting Dissolved Oxygen Level
Applied Microbiology and Biotechnology, 2009Co-Authors: Craig Frear, Shulin ChenAbstract:The culture protocol of Schizochytrium limacinum SR 21, a known docosahexaenoic acid (DHA) producing marine algae was modified in this study to better fit fermentation parameters, particularly control of Dissolved Oxygen (DO) to the known reproductive and growth biology of the microorganism. The cultures controlled at 50% DO saturation produced a cell density of 181 million cells/ml, whereas cultures with 10% DO produced only 98.4 million cells/ml. A fixed-agitation rate of 150 rpm resulted in an even lower density of 22.5 million cells/ml. Fifty percent DO saturation Level led to a decreased pH, as well as a negative correlation with lipid accumulation, while low Oxygen concentration was obligatory for lipid accumulation. This study indicated that high DO was preferred for the cells’ reproduction via release of zoospores. Thus, the culture of S. limacinum SR21 should be best divided into two stages: (1) a cell-number-increasing stage in which cell reproduction and cell number increase with little increase in the size and weight of each cell; and (2) a cell-size-increasing stage in which cells stop reproduction but cell size enlarges due to lipids accumulation. With such a protocol, the production of algae biomass and DHA was improved to Levels of 37.9 g/L and 6.56 g/L, respectively. The two-stage culture process could be potentially used not only for omega-3 PUFA production, but also in other single cell oil (SCO)-producing processes, including biodiesel production from algae.