Contamination of a high-cell-density continuous bioreactor

Domingues, Lucı́lia; Lima, Nelson; Teixeira, J. A.

doi:10.1002/(sici)1097-0290(20000605)68:5<584::aid-bit14>3.0.co;2-1

Cited by 30 publications

(20 citation statements)

References 12 publications

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“…The method of choice depends on many different factors, including the metabolism of the organism, the potential for production of inhibitory substrates and induction conditions. Batch [45], continuous [46], and a variety of fed-batch processes [39,47] have been reported for growing cells to high densities. Among these, fed-batch is the most commonly used method to produce recombinant proteins [44].…”

Section: Resultsmentioning

confidence: 99%

High level production of tyrosinase in recombinant Escherichia coli

et al. 2013

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BackgroundTyrosinase is a bifunctional enzyme that catalyzes both the hydroxylation of monophenols to o-diphenols (monophenolase activity) and the subsequent oxidation of the diphenols to o-quinones (diphenolase activity). Due to the potential applications of tyrosinase in biotechnology, in particular in biocatalysis and for biosensors, it is desirable to develop a suitable low-cost process for efficient production of this enzyme. So far, the best production yield reported for tyrosinase was about 1 g L-1, which was achieved by cultivating the filamentous fungus Trichoderma reesei for 6 days.ResultsIn this work, tyrosinase from Verrucomicrobium spinosum was expressed in Escherichia coli and its production was studied in both batch and fed-batch cultivations. Effects of various key cultivation parameters on tyrosinase production were first examined in batch cultures to identify optimal conditions. It was found that a culture temperature of 32 °C and induction at the late growth stage were favorable, leading to a highest tyrosinase activity of 0.76 U mL-1. The fed-batch process was performed by using an exponential feeding strategy to achieve high cell density. With the fed-batch process, a final biomass concentration of 37 g L-1 (based on optical density) and a tyrosinase activity of 13 U mL-1 were obtained in 28 hours, leading to a yield of active tyrosinase of about 3 g L-1. The highest overall volumetric productivity of 103 mg of active tyrosinase per liter and hour (corresponding to 464 mU L-1 h-1) was determined, which is approximately 15 times higher than that obtained in batch cultures.ConclusionsWe have successfully expressed and produced gram quantities per liter of active tyrosinase in recombinant E. coli by optimizing the expression conditions and fed-batch cultivation strategy. Exponential feed of substrate helped to prolong the exponential phase of growth, to reduce the fermentation time and thus the cost. A specific tyrosinase production rate of 103 mg L−1 h−1 and a maximum volumetric activity of 464 mU L−1 h-1 were achieved in this study. These levels have not been reported previously.

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Section: Resultsmentioning

confidence: 99%

High level production of tyrosinase in recombinant Escherichia coli

et al. 2013

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“…dilution rate with a 1 x 10 7 cells·mL -1 culture of recombinant E. coli expressing GFP (Green Fluorescent Protein). 62 When operating in continuous high-cell-density system using cheese whey permeate as substrate an ethanol productivity near 10 g·L -1 ·h -1 (corresponding to 0.45 h -1 dilution rate) was obtained 63 (Table 2). While producing ethanol, the recombinant S. cerevisiae strain cleared the cheese whey permeate of most organic substances, allowing for a significant reduction in the pollutant load of cheese whey.…”

Section: Metabolic Engineering Of Lactose Consuming/ Fermenting S Cementioning

confidence: 99%

Metabolic engineering ofSaccharomyces cerevisiaefor lactose/whey fermentation

2010

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Lactose is an interesting carbon source for the production of several bio-products by fermentation, primarily because it is the major component of cheese whey, the main by-product of dairy activities. However, the microorganism more widely used in industrial fermentation processes, the yeast Saccharomyces cerevisiae, does not have a lactose metabolization system. Therefore, several metabolic engineering approaches have been used to construct lactose-consuming S. cerevisiae strains, particularly involving the expression of the lactose genes of the phylogenetically related yeast Kluyveromyces lactis, but also the lactose genes from Escherichia coli and Aspergillus niger, as reviewed here. Due to the existing large amounts of whey, the production of bio-ethanol from lactose by engineered S. cerevisiae has been considered as a possible route for whey surplus. Emphasis is given in the present review on strain improvement for lactose-to-ethanol bioprocesses, namely flocculent yeast strains for continuous high-cell-density systems with enhanced ethanol productivity.

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“…One of the main advantages associated with the operation of yeast flocculation bioreactors is their operational stability and their resistance to contamination by other microorganisms, even those with higher specific growth rates, as it has been clearly demonstrated by Domingues et al [152]. When operating with a recombinant S. cerevisiae strain [112] at a dilution rate of 0.45 h -1 , it was possible to significantly reduce an artificially introduced bacterial contamination within 4 h. Operation stability is patent in Fig.…”

Section: Operation Of Flocculation Bioreactorsmentioning

confidence: 86%

Applications of yeast flocculation in biotechnological processes

Domingues

Vicente

Lima

et al. 2000

Biotechnol. Bioprocess Eng.

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A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects -the basics of yeast flocculation, the development of "new" flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer's yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous β-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculation bioreactors and discussing potential new uses of these systems.

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Contamination of a high-cell-density continuous bioreactor

Cited by 30 publications

References 12 publications

High level production of tyrosinase in recombinant Escherichia coli

High level production of tyrosinase in recombinant Escherichia coli

Metabolic engineering ofSaccharomyces cerevisiaefor lactose/whey fermentation

Applications of yeast flocculation in biotechnological processes

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