The Influence of Maintenance Energy and Growth Rate on the Metabolic Activity, Morphology and Conidiation of Penicillium chrysogenum

Righelato, R. C.; Trinci, Anthony P. J.; Pirt, S. J.; Peat, A.

doi:10.1099/00221287-50-3-399

Cited by 212 publications

(72 citation statements)

References 20 publications

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“…During subaerial growth, A. niger produces chains of black spores from biseriate conidiophores (55), but like other molds (15,16,56,62) it also conidiates in submerged culture in response to severe nitrogen or carbon limitation (15, 27, 46). More recent molecular studies…”

mentioning

confidence: 99%

Transcriptomic Insights into the Physiology of Aspergillus niger Approaching a Specific Growth Rate of Zero

Jørgensen

Nitsche

Lamers

et al. 2010

Appl Environ Microbiol

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The physiology of filamentous fungi at growth rates approaching zero has been subject to limited study and exploitation. With the aim of uncoupling product formation from growth, we have revisited and improved the retentostat cultivation method for Aspergillus niger. A new retention device was designed allowing reliable and nearly complete cell retention even at high flow rates. Transcriptomic analysis was used to explore the potential for product formation at very low specific growth rates. The carbon-and energy-limited retentostat cultures were highly reproducible. While the specific growth rate approached zero (<0.005 h ؊1 ), the growth yield stabilized at a minimum (0.20 g of dry weight per g of maltose). The severe limitation led to asexual differentiation, and the supplied substrate was used for spore formation and secondary metabolism. Three physiologically distinct phases of the retentostat cultures were subjected to genome-wide transcriptomic analysis. The severe substrate limitation and sporulation were clearly reflected in the transcriptome. The transition from vegetative to reproductive growth was characterized by downregulation of genes encoding secreted substrate hydrolases and cell cycle genes and upregulation of many genes encoding secreted small cysteine-rich proteins and secondary metabolism genes. Transcription of known secretory pathway genes suggests that A. niger becomes adapted to secretion of small cysteine-rich proteins. The perspective is that A. niger cultures as they approach a zero growth rate can be used as a cell factory for production of secondary metabolites and cysteine-rich proteins. We propose that the improved retentostat method can be used in fundamental studies of differentiation and is applicable to filamentous fungi in general.The filamentous fungus Aspergillus niger is one of the most important microorganisms in industrial biotechnology because of its ability to produce high levels of enzymes and organic acids (6,50,57). Apart from their biotechnological importance, filamentous fungi in the Aspergillus section Nigri (the black aspergilli) represent some of the most widespread storage molds which contaminate food and feedstocks with mycotoxins (26,37,48).Both metabolic engineering approaches and the search for optimal cultivation conditions have long been used to improve A. niger as a production host (e.g., 14, 22, 41). With the availability of the A. niger genome sequence (50), systems biology tools are being developed (4, 5, 33) which, together with new efficient methods for constructing gene knockout mutants (43), open new possibilities for further improvement of A. niger as a cell factory.A major ongoing challenge for microbial production processes is to minimize the amount of biomass formed while maintaining high productivity. Solutions to uncouple product formation from biomass accumulation or growth are therefore highly desirable. However, production at zero growth is difficult to achieve when nutrients are supplied to allow formation of a desired product. Carbon-a...

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confidence: 99%

Transcriptomic Insights into the Physiology of Aspergillus niger Approaching a Specific Growth Rate of Zero

Jørgensen

Nitsche

Lamers

et al. 2010

Appl Environ Microbiol

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“…Darlington (1964) and Johnson (1964) demonstrated that 100 grams of biomass from hydrocarbon requires approximately three times the amount of oxygen to produce the same amount of biomass from carbohydrate. Later, product formation as well as biomass production by oxygen conversion was calculated (Righelato et al, 1968, Cooney 1979.…”

Section: Oxygen Requirements Of Fermentationsmentioning

confidence: 99%

Microbubble fermentation of recombinant Pichia pastoris for human serum albumin production

Zhang¹,

Li²,

Agblevor³

2005

Process Biochemistry

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The high cell density fermentation of recombinant Pichia pastoris for human serum albumin (HSA) production is a high oxygen demand process. The oxygen demand is usually met by increased agitation rate and use of oxygen-enriched air. Microbubble fermentation however can supply adequate oxygen to the microorganisms at relatively low agitation rates because of improved mass transfer of the microbubbles used for the sparging. Conventionally sparged fermentations were conducted for the production of HSA using P. pastoris at agitation rates of 350, 500, and 750 rpm, and were compared to MBD sparged fermentation at 150, 350, and 500 rpm agitation rates. The MBD improved the volumetric oxygen transfer coefficient (k L a) and subsequently increased the cell mass and protein production compared to conventional fermentation.Cell production in MBD fermentation at 350 rpm was 4.6 times higher than that in the conventional fermentation at 350 rpm, but similar to that in the conventional 750 rpm. The volumetric oxygen transfer coefficient k L a was 1011.9 h -1 in MBD 350 rpm, which was 6.1 times higher than that in the conventional 350 rpm (164.9 h -1 ) but was similar to the conventional 750 rpm (1098 h -1 ). Therefore, MBD fermentation results at low agitation of 350 rpm were similar to those in the conventional fermentation at high agitation of 750 rpm. There was considerable improvement in oxygen transfer to the microorganism using MBD sparging relative to the conventional sparging.Conventional fermentations were conducted both in a Biostat Q fermenter (small) at 500 rpm, 750 rpm, and 1000 rpm, and in a Bioflo III fermenter (large) at 350 rpm, 500 rpm, and 750 rpm. At the same agitation rate of 500 rpm, cell production in the large reactor was 3.8 times higher than that in the small one, and no detectable protein was produced in the small reactor at 500 rpm. At the same agitation rate of 750 rpm, both cell production and protein production in the large reactor were 4.6 times higher than the small reactor. Thus, the Bioflo III fermenter showed higher oxygen transfer efficiency than the Biostat Q fermenter, because of the more efficient aeration design of the Bioflo III fermenter. ACKNOWLEDGMENTS

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“…At least ten pieces of mycelium were measured for each estimate of hyphal growth unit. Chemostat cultures were operated by using the medium and conditions described previously (Righelato et al 1968).…”

Section: Measurement Of Growth Rate and Branching In Shakeflasksmentioning

confidence: 99%

“…The simple medium was that of Righelato, Trinci, Pirt & Peat (1968) containing 30 g glucose/l. For submerged cultures I 5 ml portions were dispensed in IOO ml conical flasks.…”

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confidence: 99%

The Relationship between Hyphal Branching, Specific Growth Rate and Colony Radial Growth Rate in Penicillium chrysogenum

Morrison¹,

Righelato²

2000

Microbiology

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I N T R O D U C T I O NThe rate at which fungal colonies grow on agar has been related to their growth rate in submerged culture by using the concept of a peripheral annulus in which the mycelium grows exponentially (Trinci, 1971). It was supposed that further inside the colony the mycelium is depleted of substrate and does not contribute to radial extension of the colony. By measuring the width of the peripheral growth zone (w) and the linear colony radial growth rate (&), Trinci used eqn I (below) to calculate the specific growth rate @) for nine species of fungi. He found that the computed value coincided with the specific growth rate measured in submerged culture. We supposed that the colony radial growth rate would also be affected by the hyphal density or branching frequency, which may be a determinant of the width of the peripheral growth zone. The spreading colonial mutants of Neurospora crassa which have smaller colony radial growth rates but similar specific growth rates (Trinci, 1973 a) had a higher branching frequency than the wild type (Trinci, 1973b). Bainbridge & Trinci (1970) noted that a mutant of AspergiZlus nidulans, more branched than its parent, had an almost identical specific growth rate in submerged culture, but a substantially lower colony radial growth rate and a smaller peripheral growth zone when cultured on agar. The present work was undertaken to establish a quantitative relationship between colony growth rate and specific growth rate and hyphal branching in submerged cultures.The expression used by Pirt (1967) andTrinci (1971) to represent the linear colony radial growth rate wasdt This can be re-written in which b is a measurement of hyphal density and k a constant. Hyphal density can be directly related to branching frequency if the internode length is used or the total hyphal length divided by the number of growing tips. We have used eqn 2 to relate measurements of specific growth rate and hyphal branching in submerged culture to colony radial growth rate on agar.

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The Influence of Maintenance Energy and Growth Rate on the Metabolic Activity, Morphology and Conidiation of Penicillium chrysogenum

Cited by 212 publications

References 20 publications

Transcriptomic Insights into the Physiology of Aspergillus niger Approaching a Specific Growth Rate of Zero

Transcriptomic Insights into the Physiology of Aspergillus niger Approaching a Specific Growth Rate of Zero

Microbubble fermentation of recombinant Pichia pastoris for human serum albumin production

The Relationship between Hyphal Branching, Specific Growth Rate and Colony Radial Growth Rate in Penicillium chrysogenum

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