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Tan Y, Stein LY, Sauvageau D. Methanol bioconversion in Methylotuvimicrobium buryatense 5GB1C through self-cycling fermentation. Bioprocess Biosyst Eng 2023:10.1007/s00449-023-02876-3. [PMID: 37160768 DOI: 10.1007/s00449-023-02876-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Accepted: 04/18/2023] [Indexed: 05/11/2023]
Abstract
Methanol is an abundant and low-cost next-generation carbon source. While many species of methanotrophic bacteria can convert methanol into valuable bioproducts in bioreactors, Methylotuvimicrobium buryatense 5GB1C stands out as one of the most promising strains for industrialization. It has a short doubling time compared to most methanotrophs, remarkable resilience against contamination, and a suite of tools enabling genetic engineering. When approaching industrial applications, growing M. buryatense 5GB1C on methanol using common batch reactor operation has important limitations; for example methanol toxicity leads to mediocre biomass productivity. Advanced bioreactor operation strategies, such as fed-batch and self-cycling fermentation, have the potential to greatly improve the industrial prospects of methanotrophs growing on methanol. Herein, implementation of fed-batch operation led to a 26-fold increase in biomass density, while two different self-cycling fermentation (SCF) strategies led to 3-fold and 10-fold increases in volumetric biomass productivity. Interestingly, while synchronization is a typical trait of microbial populations undergoing SCF, M. buryatense 5GB1C cultures growing under this mode of operation led to stable, reproducible cycles but no significant synchronization.
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Affiliation(s)
- Yusheng Tan
- Department of Chemical and Materials Engineering, University of Alberta, 9211-116 St. NW, Edmonton, AB, T6G 1H9, Canada
| | - Lisa Y Stein
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering, University of Alberta, 9211-116 St. NW, Edmonton, AB, T6G 1H9, Canada.
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Tan Y, Stein LY, Sauvageau D. The influence of self-cycling fermentation long- and short-cycle schemes on Saccharomyces cerevisiae and Escherichia coli. Sci Rep 2022; 12:13154. [PMID: 35915208 PMCID: PMC9343364 DOI: 10.1038/s41598-022-16831-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/18/2022] [Indexed: 11/09/2022] Open
Abstract
Self-cycling fermentation (SCF), a cyclic process in which cells, on average, divide once per cycle, has been shown to lead to whole-culture synchronization and improvements in productivity during bioconversion. Previous studies have shown that the completion of synchronized cell replication sometimes occurs simultaneously with depletion of the limiting nutrient. However, cases in which the end of cell doubling occurred before limiting nutrient exhaustion were also observed. In order to better understand the impact of these patterns on bioprocessing, we investigated the growth of Saccharomyces cerevisiae and Escherichia coli in long- and short-cycle SCF strategies. Three characteristic events were identified during SCF cycles: (1) an optimum in control parameters, (2) the time of completion of synchronized cell division, and (3) the depletion or plateau of the limiting nutrient. Results from this study and literature led to the identification of three potential trends in SCF cycles: (A) co-occurrence of the three key events, (B) cell replication ending prior to the co-occurrence of the other two events, and (C) depletion or plateau of the limiting nutrient occurring later than the co-occurrence of the other two events. Based on these observations, microbial physiological differences were analyzed and a novel definition for SCF is proposed.
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Affiliation(s)
- Yusheng Tan
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada
| | - Lisa Y Stein
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada.
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Tan Y, Agustin RVC, Stein LY, Sauvageau D. Transcriptomic analysis of synchrony and productivity in self-cycling fermentation of engineered yeast producing shikimic acid. BIOTECHNOLOGY REPORTS (AMSTERDAM, NETHERLANDS) 2021; 32:e00691. [PMID: 34934640 PMCID: PMC8660916 DOI: 10.1016/j.btre.2021.e00691] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 11/09/2021] [Accepted: 11/23/2021] [Indexed: 05/25/2023]
Abstract
Industrial fermentation provides a wide variety of bioproducts, such as food, biofuels and pharmaceuticals. Self-cycling fermentation (SCF), an advanced automated semi-continuous fermentation approach, has shown significant advantages over batch reactors (BR); including cell synchrony and improved production. Here, Saccharomyces cerevisiae engineered to overproduce shikimic acid was grown under SCF operation. This led to four-fold increases in product yield and volumetric productivity compared to BR. Transcriptomic analyses were performed to understand the cellular mechanisms leading to these increases. Results indicate an up-regulation of a large number of genes related to the cell cycle and DNA replication in the early stages of SCF cycles, inferring substantial synchronization. Moreover, numerous genes related to gluconeogenesis, the citrate cycle and oxidative phosphorylation were significantly up-regulated in the late stages of SCF cycles, consistent with significant increases in shikimic acid yield and productivity.
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Key Words
- BR, Batch reactor
- CER, Carbon dioxide evolution rate
- DDT, Dithiothreitol
- DNA, Deoxyribonucleic acid
- EDTA, Ethylenediaminetetraacetic acid
- FC, Fold change
- OD600, Optical density at 600 nm
- RNA, Ribonucleic acid
- SCF, Self-cycling fermentation
- STP, Standard temperature and pressure
- Saccharomyces cerevisiae
- Self-cycling fermentation (SCF)
- Shikimic acid
- Synchrony
- Transcriptomics
- cDNA, Complementary deoxyribonucleic acid
- mRNA, Messenger ribonucleic acid
- qPCR, Quantitative polymerase chain reaction
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Affiliation(s)
- Yusheng Tan
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Roman Vincent C. Agustin
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Lisa Y. Stein
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
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Wang J, Chae M, Beyene D, Sauvageau D, Bressler DC. Co-production of ethanol and cellulose nanocrystals through self-cycling fermentation of wood pulp hydrolysate. BIORESOURCE TECHNOLOGY 2021; 330:124969. [PMID: 33740586 DOI: 10.1016/j.biortech.2021.124969] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/05/2021] [Accepted: 03/06/2021] [Indexed: 06/12/2023]
Abstract
A promising approach to help offset production costs for the cellulosic ethanol industry is to improve ethanol productivity while simultaneously generating value-added by-products. This study reports integration of an advanced fermentation approach (self-cycling fermentation) with the production of cellulose nanocrystals. Specifically, wood pulp was enzymatically hydrolyzed to yield dissolved sugars, which were fed to a self-cycling fermentation system for ethanol production, and residual solids were used for cellulose nanocrystals production via acid hydrolysis. Self-cycling fermentation achieved stable ethanol production for 10 cycles with significantly greater productivity than batch operation: ethanol volumetric productivity increased by 63-95% and annual ethanol productivity by 96 ± 5%. Additionally, the enzyme hydrolysis approach employed did not impede ethanol fermentation, and the cellulose nanocrystals generated displayed properties consistent with previous studies. Taken together, these results highlight the potential of this co-production strategy to produce both cellulosic ethanol and cellulose nanocrystals from a single feedstock.
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Affiliation(s)
- Jie Wang
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada
| | - Michael Chae
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada
| | - Dawit Beyene
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Canada
| | - David C Bressler
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton T6G 2P5, Canada.
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Feng S, Lin Y. Development of dissolved carbon dioxide‐driven‐and‐controlled repeated batch fermentation process for ethanol production. CAN J CHEM ENG 2020. [DOI: 10.1002/cjce.23822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sijing Feng
- Department of Chemical and Biological Engineering University of Saskatchewan Saskatoon Saskatchewan Canada
| | - Yen‐Han Lin
- Department of Chemical and Biological Engineering University of Saskatchewan Saskatoon Saskatchewan Canada
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Wang J, Chae M, Bressler DC, Sauvageau D. Improved bioethanol productivity through gas flow rate-driven self-cycling fermentation. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:14. [PMID: 31998407 PMCID: PMC6979077 DOI: 10.1186/s13068-020-1658-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Accepted: 01/16/2020] [Indexed: 05/25/2023]
Abstract
BACKGROUND The growth of the cellulosic ethanol industry is currently impeded by high production costs. One possible solution is to improve the performance of fermentation itself, which has great potential to improve the economics of the entire production process. Here, we demonstrated significantly improved productivity through application of an advanced fermentation approach, named self-cycling fermentation (SCF), for cellulosic ethanol production. RESULTS The flow rate of outlet gas from the fermenter was used as a real-time monitoring parameter to drive the cycling of the ethanol fermentation process. Then, long-term operation of SCF under anaerobic conditions was improved by the addition of ergosterol and fatty acids, which stabilized operation and reduced fermentation time. Finally, an automated SCF system was successfully operated for 21 cycles, with robust behavior and stable ethanol production. SCF maintained similar ethanol titers to batch operation while significantly reducing fermentation and down times. This led to significant improvements in ethanol volumetric productivity (the amount of ethanol produced by a cycle per working volume per cycle time)-ranging from 37.5 to 75.3%, depending on the cycle number, and in annual ethanol productivity (the amount of ethanol that can be produced each year at large scale)-reaching 75.8 ± 2.9%. Improved flocculation, with potential advantages for biomass removal and reduction in downstream costs, was also observed. CONCLUSION Our successful demonstration of SCF could help reduce production costs for the cellulosic ethanol industry through improved productivity and automated operation.
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Affiliation(s)
- Jie Wang
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5 Canada
| | - Michael Chae
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5 Canada
| | - David C. Bressler
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5 Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, T6G 1H9 Canada
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Wang J, Chae M, Sauvageau D, Bressler DC. Improving ethanol productivity through self-cycling fermentation of yeast: a proof of concept. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:193. [PMID: 28785309 PMCID: PMC5541432 DOI: 10.1186/s13068-017-0879-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 07/19/2017] [Indexed: 05/25/2023]
Abstract
BACKGROUND The cellulosic ethanol industry has developed efficient strategies for converting sugars obtained from various cellulosic feedstocks to bioethanol. However, any further major improvements in ethanol productivity will require development of novel and innovative fermentation strategies that enhance incumbent technologies in a cost-effective manner. The present study investigates the feasibility of applying self-cycling fermentation (SCF) to cellulosic ethanol production to elevate productivity. SCF is a semi-continuous cycling process that employs the following strategy: once the onset of stationary phase is detected, half of the broth volume is automatically harvested and replaced with fresh medium to initiate the next cycle. SCF has been shown to increase product yield and/or productivity in many types of microbial cultivation. To test whether this cycling process could increase productivity during ethanol fermentations, we mimicked the process by manually cycling the fermentation for five cycles in shake flasks, and then compared the results to batch operation. RESULTS Mimicking SCF for five cycles resulted in regular patterns with regards to glucose consumption, ethanol titer, pH, and biomass production. Compared to batch fermentation, our cycling strategy displayed improved ethanol volumetric productivity (the titer of ethanol produced in a given cycle per corresponding cycle time) and specific productivity (the amount of ethanol produced per cellular biomass) by 43.1 ± 11.6 and 42.7 ± 9.8%, respectively. Five successive cycles contributed to an improvement of overall productivity (the aggregate amount of ethanol produced at the end of a given cycle per total processing time) and the estimated annual ethanol productivity (the amount of ethanol produced per year) by 64.4 ± 3.3 and 33.1 ± 7.2%, respectively. CONCLUSIONS This study provides proof of concept that applying SCF to ethanol production could significantly increase productivities, which will help strengthen the cellulosic ethanol industry.
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Affiliation(s)
- Jie Wang
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5 Canada
| | - Michael Chae
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5 Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, T6G 1H9 Canada
| | - David C. Bressler
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5 Canada
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Storms ZJ, Brown T, Cooper DG, Sauvageau D, Leask RL. Impact of the cell life-cycle on bacteriophage T4 infection. FEMS Microbiol Lett 2014; 353:63-8. [DOI: 10.1111/1574-6968.12402] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Zachary J. Storms
- Department of Chemical Engineering; McGill University; Montreal QC Canada
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton AB Canada
| | - Tobin Brown
- Department of Chemical Engineering; McGill University; Montreal QC Canada
| | - David G. Cooper
- Department of Chemical Engineering; McGill University; Montreal QC Canada
| | - Dominic Sauvageau
- Department of Chemical and Materials Engineering; University of Alberta; Edmonton AB Canada
| | - Richard L. Leask
- Department of Chemical Engineering; McGill University; Montreal QC Canada
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Storms ZJ, Brown T, Sauvageau D, Cooper DG. Self-cycling operation increases productivity of recombinant protein in Escherichia coli. Biotechnol Bioeng 2012; 109:2262-70. [DOI: 10.1002/bit.24492] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 02/09/2012] [Accepted: 02/27/2012] [Indexed: 11/07/2022]
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Sauvageau D, Cooper DG. Two-stage, self-cycling process for the production of bacteriophages. Microb Cell Fact 2010; 9:81. [PMID: 21040541 PMCID: PMC2989940 DOI: 10.1186/1475-2859-9-81] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Accepted: 11/01/2010] [Indexed: 11/26/2022] Open
Abstract
Background A two-stage, self-cycling process for the production of bacteriophages was developed. The first stage, containing only the uninfected host bacterium, was operated under self-cycling fermentation (SCF) conditions. This automated method, using the derivative of the carbon dioxide evolution rate (CER) as the control parameter, led to the synchronization of the host bacterium. The second stage, containing both the host and the phage, was operated using self-cycling infection (SCI) with CER and CER-derived data as the control parameters. When each infection cycle was terminated, phages were harvested and a new infection cycle was initiated by adding host cells from the SCF (first stage). This was augmented with fresh medium and the small amount of phages left from the previous cycle initiated the next infection cycle. Both stages were operated independently, except for this short period of time when the SCF harvest was added to the SCI to initiate the next cycle. Results It was demonstrated that this mode of operation resulted in stable infection cycles if the growth of the host cells in the SCF was synchronized. The final phage titers obtained were reproducible among cycles and were as good as those obtained in batch productions performed under the same conditions (medium, temperature, initial multiplicity of infection, etc.). Moreover, phages obtained in different cycles showed no important difference in infectivity. Finally, it was shown that cell synchronization of the host cells in the first stage (SCF) not only maintained the volumetric productivity (phages per volume) but also led to higher specific productivity (phage per cell per hour) in the second stage (SCI). Conclusions Production of bacteriophage T4 in the semi-continuous, automated SCF/SCI system was efficient and reproducible from cycle to cycle. Synchronization of the host in the first stage prior to infection led to improvements in the specific productivity of phages in the second stage while maintaining the volumetric productivity. These results demonstrate the significant potential of this approach for both upstream and downstream process optimization.
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Affiliation(s)
- Dominic Sauvageau
- Department of Chemical Engineering, McGill University, 3610 University, Montreal, Quebec, H3A 2B2, Canada
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Khire JM. Bacterial Biosurfactants, and Their Role in Microbial Enhanced Oil Recovery (MEOR). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 672:146-57. [DOI: 10.1007/978-1-4419-5979-9_11] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Godin FB, Cooper DG, Rey AD. Numerical methods for a population-balance model of a periodic fermentation process. AIChE J 2006. [DOI: 10.1002/aic.690450621] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Tam K, Matsumoto MR, Sheppard JD. A kinetic model for suspended and attached growth of a defined mixed culture. Biotechnol Prog 2005; 21:720-7. [PMID: 15932248 DOI: 10.1021/bp0500720] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Kinetic experiments were carried out in a semicontinuous wastewater treatment process called self-cycling fermentation (SCF) using a defined mixed culture and various concentrations of synthetic brewery wastewater. The same consortium, which had been previously identified as Acinetobacter sp., Enterobacter sp., and Candida sp., were used in these experiments. The overall rate of substrate removal was attributable to both suspended microbes and the biofilm that formed during the treatment process. A rate expression was developed for the SCF system for a range of synthetic wastewaters containing glucose and various initial concentrations of ethanol and maltose. The data indicated that substrate removal by the suspended cells was directly related to the biomass concentration. However, substrate removal by the biofilm was apparently not affected by the biofilm thickness and was a function of substrate concentration only.
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Affiliation(s)
- Kawai Tam
- Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA
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Sarubbo LA, Porto AL, Campos-Takaki GM. The use of babassu oil as substrate to produce bioemulsifiers by Candida lipolytica. Can J Microbiol 1999; 45:423-6. [PMID: 10446719 DOI: 10.1139/w99-025] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Candida lipolytica IA 1055 produced an extracellular emulsifier when using babassu oil as its sole carbon source during batch and fed batch fermentations at 27 degrees C. Emulsification activity was detected after 60 h of growth in all conditions studied. The bioemulsifier was isolated after 144 h of fermentation from the best condition studied. The biopolymer seems to be a polysaccharide-protein-lipid complex.
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Affiliation(s)
- L A Sarubbo
- Laboratório de Imunopatologia Keizo Asami, Cidade universitária, Recife, PE, Brasil
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Abstract
Bioemulsans are amphipathic proteins and/or polysaccharides that stabilize oil-in-water emulsions. Bioemulsans are produced by a wide diversity of microorganisms and have potential applications in the food, paper, paint, bioremediation, agriculture, detergent and cosmetics industries. The production of the RAG-1 emulsan has been studied in batch-fed fermentors via self-cycling fermentation and with immobilized cells using a Celite support matrix. Bioemulsans have several advantages over lower molecular weight emulsifiers presently used in industry. The last few years have seen a number of new bioemulsans described with commercial applications.
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Affiliation(s)
- E Rosenberg
- Department of Molecular Microbiology & Biotechnology, Tel Aviv University, Ramat Aviv, Israel.
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McCaffrey WC, Cooper DG. Sophorolipids production by Candida bombicola using self-cycling fermentation. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0922-338x(95)94082-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Antibiotic production byStreptomyces aureofaciens using self-cycling fermentation. Biotechnol Bioeng 1994; 44:1331-6. [DOI: 10.1002/bit.260441109] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Sarkis BE, Cooper DG. Biodegradation of aromatic compounds in a self-cycling fermenter (SCF). CAN J CHEM ENG 1994. [DOI: 10.1002/cjce.5450720514] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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van Walsum GP, Cooper DG. Self-cycling fermentation in a stirred tank reactor. Biotechnol Bioeng 1993; 42:1175-80. [PMID: 18609666 DOI: 10.1002/bit.260421007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Self-cycling fermentations (SCFs) were conducted in a stirred tank apparatus using Bacillus subtilis and Acinetobacter calcoaceticus. The systems were very stable and the experiments lasted through many cycles. The variation of parameters such as biomass and doubling time from cycle to cycle was small. The stirred tank reactor (STR) allowed a much better control of the working volume in the fermentor from cycle to cycle, compared to the cyclone column, and it was not necessary to make periodic corrections.The production of surfactin from B. subtilis was achieved without extending the cycle time. The harvested broth at the end of each cycle was allowed to remain in a secondary vessel, at ambient temperature, before being collected. It is exhaustion of the limiting nutrient which causes an increase in dissolved oxygen (DO). At this point, the computer, which constantly monitors the DO, triggered the harvesting sequence to end the cycle. Thus, the mature culture in the secondary vessel experienced appropriate conditions for the production of the secondary metabolite. Meanwhile, the next batch of cells was being grown in the primary reactor.The response of a gas analyzer on the effluent paralleled that of the DO measurements in the fermentor. These data for oxygen and carbon dioxide exhibited less noise than the DO readings. Either would be a more reliable parameter for feedback control of the SCF because the problem of fouling of the DO probe after extended runs of many cycles would be eliminated.
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Affiliation(s)
- G P van Walsum
- Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada
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Brown WA, Cooper DG. Hydrocarbon degradation byAcinetobacter calcoaceticus RAG-1 using the self-cycling fermentation technique. Biotechnol Bioeng 1992; 40:797-805. [DOI: 10.1002/bit.260400707] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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