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1.
Dragan Miscevic Ju-Yi Mao Murray Moo-Young Chih-Hsiung Perry Chou 《Biotechnology and bioengineering》2020,117(5):1304-1315
A propanologenic (i.e., 1-propanol-producing) bacterium Escherichia coli strain was previously derived by activating the genomic sleeping beauty mutase (Sbm) operon. The activated Sbm pathway branches out of the tricarboxylic acid (TCA) cycle at the succinyl-CoA node to form propionyl-CoA and its derived metabolites of 1-propanol and propionate. In this study, we targeted several TCA cycle genes encoding enzymes near the succinyl-CoA node for genetic manipulation to identify the individual contribution of the carbon flux into the Sbm pathway from the three TCA metabolic routes, that is, oxidative TCA cycle, reductive TCA branch, and glyoxylate shunt. For the control strain CPC-Sbm, in which propionate biosynthesis occurred under relatively anaerobic conditions, the carbon flux into the Sbm pathway was primarily derived from the reductive TCA branch, and both succinate availability and the SucCD-mediated interconversion of succinate/succinyl-CoA were critical for such carbon flux redirection. Although the oxidative TCA cycle normally had a minimal contribution to the carbon flux redirection, the glyoxylate shunt could be an alternative and effective carbon flux contributor under aerobic conditions. With mechanistic understanding of such carbon flux redirection, metabolic strategies based on blocking the oxidative TCA cycle (via ∆sdhA mutation) and deregulating the glyoxylate shunt (via ∆iclR mutation) were developed to enhance the carbon flux redirection and therefore propionate biosynthesis, achieving a high propionate titer of 30.9 g/L with an overall propionate yield of 49.7% upon fed-batch cultivation of the double mutant strain CPC-Sbm∆sdhA∆iclR under aerobic conditions. The results also suggest that the Sbm pathway could be metabolically active under both aerobic and anaerobic conditions. 相似文献
2.
A Domínguez E Fermi?án M Sánchez F J González F M Pérez-Campo S García A B Herrero A San Vicente J Cabello M Prado F J Iglesias A Choupina F J Burguillo L Fernández-Lago M C López 《International microbiology》1998,1(2):131-142
Yeasts are an attractive group of lower eukaryotic microorganisms, some of which are used in several industrial processes that include brewing, baking and the production of a variety of biochemical compounds. More recently, yeasts have been developed as host organisms for the production of foreign (heterologous) proteins. Saccharomyces cerevisiae has usually been the yeast of choice, but an increasing number of alternative non-Saccharomyces yeasts has now become accessible for modern molecular genetics techniques. Some of them exhibit certain favourable traits such as high-level secretion or very strong and tightly regulated promoters, offering significant advantages over traditional bakers' yeast. In the present work, the current status of Kluyveromyces lactis, Yarrowia lipolytica, Hansenula polymorpha and Pichia pastoris (the best-known alternative yeast systems) is reviewed. The advantages and limitations of these systems are discussed in relation to S. cerevisiae. 相似文献
3.
Glycerol production by a highly glycerol-producing local isolate (Eurotium amstelodami) and a standard reference isolate (Aspergillus wentii) was markedly enhanced by high saline media. Glycerol concentration depended on the external osmotic. Thus, the highest glycerol
concentration was found in the presence of NaCl, followed by KCl, with considerably lower values for MgCl2 and CaCl2 saline media. With glucose (5–50%) used as a nonionic osmotic, low levels of glycerol were obtained and the main pool of
polyols was mannitol. Glycerol production was gradually increased with the increase of NaCl concentration of cheese whey,
reaching maxima by both organisms when whey was supplemented with 8% NaCl (total of 16% NaCl). The quantity of glycerol produced
byA. wentii was twice higher than that obtained byE. amstelodami on whey treated with 8% NaCl. 相似文献
4.
Sung-Woo Kim Jae-Bum Kim Ji-Myung Ryu Joon-Ki Jung Jung-Hoe Kim 《Process Biochemistry》2009,44(8):899-905
Recombinant lycopene was generated by utilizing metabolically engineered Escherichia coli with yields being dependent upon inocula state. Yields were especially low in the case of cultures harboring high-copy plasmids that were established with inocula at the stationary growth phase. On the other hand, cultures derived using low-copy plasmid, however, yielded high amounts of lycopene irrespective of inocula state. Nevertheless, it showed still an inocula dependence pattern in lycopene productivity (mg/l/h). To further increase lycopene productivity, we applied a temperature-shift culture technique (37 → 25 °C). Using this method, we effectively enhanced lycopene productivity without any problematic phenomena. As a result, we were able to increase lycopene yield by approximately 20% compared to previous culture methods. In the present study, we were able to reach a final lycopene yield up to 260 mg/l for 60 h, which corresponds to the highest titer to date for the production of lycopene in E. coli. 相似文献
5.
Bacterial fermentation of cheese whey for production of a ruminant feed supplement rich in curde protein. 下载免费PDF全文
A simple and efficient process for the production of a ruminant feed supplement, rich in crude protein (defined as total N X 6.25), by bacterial fermentation of cheese whey has been developed. The lactose in unpasteurized whey is fermented to lactate acid by Lactobacillus bulgaricus at a temperature of 43 degrees C and pH 5.5. The lactic acid produced is continually neutralized with ammonia to form ammonium lactate. The fermented product is concentrated by evaporation to a solids content of about 70% and adjusted to pH 6.8 with additional ammonia. The concentrated product contains about 55% crude protein. Approximately 6 to 8% of the crude protein is derived from bacterial cells. 17% from whey proteins, and 75 to 77% from ammonium lactate. The efficiency of conversion of lactose to lactic acid usually exceeds 95%. The fermentation time is greatly reduced upon the addition of 0.2% yeast extract or 0.1% corn steep liquor as a source of growth factors. Whey containing lactose at concentrations up to 7% can be fermented efficiently, but at higher concentrations lactose is fermented incompletely. The process has been scaled up to a pilot plant level, and 40 tons of concentrated product were produced fro animal feeding trials, without ever encountering putrefactive spoilage. 相似文献
6.
Thirteen yeast species belonging to nine genera were screened for the production of single-cell protein (SCP) using cheese whey as the substrate. Cheese whey supplemented with minerals and yeast extract proved to the best medium for yield, lactose utilization, biomass production, and conversion efficiency. Production of beta-galactosidase was studied in Brettanomyces anomalus, Kluyveromyces fragilis, Trichosporon cutaneum, and Wingea robertsii; the last proved to be the best strain combining high yield with shorter incubation period. 相似文献
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A simple and efficient process for the production of a ruminant feed supplement, rich in crude protein (defined as total N X 6.25), by bacterial fermentation of cheese whey has been developed. The lactose in unpasteurized whey is fermented to lactate acid by Lactobacillus bulgaricus at a temperature of 43 degrees C and pH 5.5. The lactic acid produced is continually neutralized with ammonia to form ammonium lactate. The fermented product is concentrated by evaporation to a solids content of about 70% and adjusted to pH 6.8 with additional ammonia. The concentrated product contains about 55% crude protein. Approximately 6 to 8% of the crude protein is derived from bacterial cells. 17% from whey proteins, and 75 to 77% from ammonium lactate. The efficiency of conversion of lactose to lactic acid usually exceeds 95%. The fermentation time is greatly reduced upon the addition of 0.2% yeast extract or 0.1% corn steep liquor as a source of growth factors. Whey containing lactose at concentrations up to 7% can be fermented efficiently, but at higher concentrations lactose is fermented incompletely. The process has been scaled up to a pilot plant level, and 40 tons of concentrated product were produced fro animal feeding trials, without ever encountering putrefactive spoilage. 相似文献
9.
紫苏醇,即[4-异丙烯基-1-环己烯]甲醇,是一种具有类似芳樟醇和松油醇特殊气味的单环单萜烯醇。在医药、食品和化妆品等行业具有广阔市场空间和研究价值。文中研究了以工程大肠杆菌通过甲羟戊酸途径合成紫苏醇的方法。首先在大肠杆菌中构建来源于粪肠球菌的MVA代谢途径合成柠檬烯,随后柠檬烯通过细胞色素P450烷烃羟化酶的羟基化转化为紫苏醇。然后将构建的紫苏醇合成菌株在摇瓶发酵条件下进行优化,研究发现工程大肠杆菌以葡萄糖为原料,通过MVA代谢途径可合成约50.12 mg/L的紫苏醇。本研究构建合成紫苏醇的MVA代谢途径也可用于其他萜类化合物的合成,为今后生物法合成萜类化合物提供了理论依据和技术支持。 相似文献
10.
A mathematical model describing the kinetics of continuous production of single cell protein from cheese whey using Kluyveromyces fragilis was developed from the basic principles of mass balance. The model takes into account the substrate utilization for growth and maintenance and the effect of substrate concentration and cell death rate on the net cell growth and substrate utilization during the fermentation process. A lactose concentration below 1.91 g/L limited growth of yeast cells whereas a lactose concentration above 75 g/L inhibited the growth of the yeast. The model was tested using experimental data obtained from a continuous system operated at various retention times (12, 18 and 24 h), mixing speeds (200, 400 and 600 rpm) and air flow rates (1 and 3 vvm). The model was capable of predicting the effluent cell and substrate concentrations with R2 ranging from 0.95 to 0.99. The viable cell mass and lactose consumption ranged from 1.3 to 34.3 g/L and from 74.31% to 99.02%, respectively. A cell yield of 0.74 g cell/g lactose (close to the stoichiometric value of 0.79 g cell/g lactose) was achieved at the 12 h retention time-3 vvm air flow rate-600 rpm mixing speed combination. The total biomass output (viable and dead cells) at this combination was 37 g/L. 相似文献
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Summary A filamentous fungus Penicillium cyclopium, capable of growing on deproteinized whey was isolated and characterized for the purpose of production of microbial protein.This organism has a maximum specific growth rate of 0.2 h–1 at pH 3.0 to 4.5 and 28°C in a medium containing only ammonium nitrogen and deproteinized whey. The yield coefficients are 0.68 g biomass/g lactose, 12.0 g biomass/g nitrogen, and 2.10 g biomass/g oxygen, respectively.Crude protein and total nucleic acid contents of this organism are 47.5% and 7.4% (dry cell weight basis), respectively. The profile of essential amino acids shows that it could be a good source of animal feed or food protein. 相似文献
13.
Frengova GI Emilina SD Beshkova DM 《Zeitschrift für Naturforschung. C, Journal of biosciences》2003,58(7-8):562-567
Two strains were selected--the lactoso-negative yeast Rhodotorula rubra GED2 and the homofermentative Lactobacillus casei subsp. casei Ha1 for co-cultivation in cheese whey ultrafiltrate (WU) and active synthesis of carotenoids. Under conditions of intensive aeration (1.0 l/l min, 220 rpm), a temperature of 30 degrees C, WU with 55.0 g lactose/l, initial pH = 5.5, the carotenoid content in the cells reached a maximum, when the growth of the cultures had come to an end, i.e. in the stationary phase of the yeast. The maxima for dry cell accumulation (27.0 g/l) and carotenoid formation (12.1 mg/l culture medium) did not coincide on the 5th and 6th day, respectively. A peculiarity of the carotenoid-synthesizing Rh. rubra GED2 strain, co-cultivated with L. casei Ha1, was the production of carotenoids with high beta-carotene content (46.6% of total carotenoids) and 10.7% and 36.9% for torulene and torularhodin, respectively. 相似文献
14.
Recombinant protein production in yeasts 总被引:8,自引:0,他引:8
Recombinant DNA (rDNA) technologies (genetic, protein, and metabolic engineering) allow the production of a wide range of
peptides, proteins, and biochemicals from naturally nonproducing cells. These technologies, now approx 25 yr old, have become
one of the most important technologies developed in the twentieth century. Pharmaceutical products and industrial enzymes
were the first biotech products on the world market made by means of rDNA. Despite important advances in rDNA applications
in mammalian cells, yeasts still represent attractive hosts for the production of heterologous proteins. In this review we
summarize advantages and limitations of the main and most promising yeast hosts. 相似文献
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The survival of Listeria monocytogenes in cottage cheese 总被引:1,自引:0,他引:1
Because of the difficulty of ensuring that cottage cheese is produced in conditions that prevent contamination with Listeria monocytogenes, the ability of this bacterium to survive in cottage cheese from three sources was investigated (a) during shelf-life at chill temperature and (b) in conditions of temperature abuse. Three batches of creamed cottage cheese, from three sources, received within 24 h of production, were inoculated with L. monocytogenes strain F6861 and stored at 4, 8 or 12 degrees C for 14 d. The three batches differed in their initial pH, titratable acidity and content of lactic acid and of lactic acid bacteria. No increase in numbers of L. monocytogenes occurred in the cottage cheeses during storage in these conditions. The numbers of listeria decreased; the rate of decrease differed in products from the three sources and was least in the product with the highest pH and lowest content of lactic acid. Acid formation by lactic acid bacteria during storage of the products probably contributed to the inhibition of listeria. 相似文献
17.
The survival of Listeria monocytogenes in cottage cheese 总被引:1,自引:0,他引:1
Because of the difficulty of ensuring that cottage cheese is produced in conditions that prevent contamination with Listeria monocytogenes , the ability of this bacterium to survive in cottage cheese from three sources was investigated (a) during shelf-life at chill temperature and (b) in conditions of temperature abuse. Three batches of creamed cottage cheese, from three sources, received within 24 h of production, were inoculated with L. monocytogenes strain F6861 and stored at 4, 8 or 12°C for 14 d. The three batches differed in their initial pH, titratable acidity and content of lactic acid and of lactic acid bacteria. No increase in numbers of L. monocytogenes occurred in the cottage cheeses during storage in these conditions. The numbers of listeria decreased; the rate of decrease differed in products from the three sources and was least in the product with the highest pH and lowest content of lactic acid. Acid formation by lactic acid bacteria during storage of the products probably contributed to the inhibition of listeria. 相似文献
18.
We have demonstrated that the method of chemical induction using a chemically inducible viral amplicon expression system can be optimized to increase expression of a heterologous protein in plants. A cucumber mosaic virus inducible viral amplicon (CMViva) expression system was used to transiently produce a recombinant human blood protein, alpha-1-antitrypsin (AAT), by co-infiltrating intact and detached Nicotiana benthamiana leaves with two Agrobacterium tumefaciens strains, one containing the CMViva expression cassette carrying the AAT gene and the other containing a binary vector carrying the gene silencing suppressor p19. Infiltrated plants were induced by either topical applications or pressure injections and inducer was applied at either a single or multiple time points. Applying induction solution every 2 days via topical application resulted in increasing maximum levels of biologically functional rAAT from 0.71% to 1.3% of the total soluble protein (TSP) in detached plant leaves, a 1.8-fold improvement. Multiple applications of induction solution via pressure injection into intact leaves resulted in maximum levels of biologically functional rAAT being elevated 3-fold up to 2.4% of TSP compared to 0.8% of TSP when using the conventional method of a single topical application, and expression levels remained high 6 days post-induction. Overall production of rAAT in intact leaves was found to have a maximum level of 5.8% of TSP or 390 mg rAAT per kg leaf tissue when applying multiple injections of chemical induction solution. 相似文献
19.
Karla Silva Teixeira Souza Cintia Lacerda Ramos Rosane Freitas Schwan 《Preparative biochemistry & biotechnology》2017,47(4):357-363
The main carbon source used for growth by four yeast strains (Yarrowia lipolytica CCMA 0357, Y. lipolytica CCMA 0242, Wickerhamomyces anomalus CCMA 0358, and Cryptococcus humicola CCMA 0346) and their lipid production were evaluated, using different concentrations of crude and pure glycerol and glucose. Whereas crude glycerol (100?g/L) was the main carbon source used by Y. lipolytica CCMA 0357 (nearly 15?g/L consumed at 120?hr) and W. anomalus CCMA 0358 (nearly 45.10?g/L consumed at 48?hr), pure glycerol (150?g/L) was the main one used by C. humicola CCMA 0346 (nearly 130?g/L consumed). On the other hand, Y. lipolytica CCMA 0242 used glucose (100?g/L) as its main source of carbon (nearly 96.48?g/L consumed). Y. lipolytica CCMA 0357 demonstrated the highest lipid production [about 70% (wt/wt)], forming palmitic (45.73% of fatty acid composition), stearic (16.43%), palmitoleic (13.29%), linolenic (10.77%), heptadecanoic (4.07%), and linoleic (14.14%) acids. Linoleic acid, an essential fatty acid, was produced by all four yeast strains but in varying degrees, representing 70.42% of the fatty acid profile of lipids produced by C. humicola CCMA 0346. 相似文献
20.
Daesoo Kim Greg Thoma Darin Nutter Franco Milani Rick Ulrich Greg Norris 《The International Journal of Life Cycle Assessment》2013,18(5):1019-1035