Organic Acid Production by Aspergillus niger in Recycling Culture Analyzed by Capillary Electrophoresis

Schrickx, J.M.; Raedts, M.J.H.; Stouthamer, A. H.; Vanverseveld, H.W.

doi:10.1006/abio.1995.1518

Cited by 30 publications

(13 citation statements)

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“…In addition, only trace amounts of oxalic acid were produced during batch cultivation in the 5-L bioreactor, while during growth in the batch phase of the fed-batch cultivation, the concentration of oxalic acid already reached 2 g‚L -1 concomitant with a lower amount of biomass being produced ( Figures 3A and 4A). The formation of oxalic acid by A. niger is not unusual, and its formation during growth on various carbon sources has been reported previously (38,39). However, a deeper understanding of the influence of culture conditions on the physiology of organic acid (e.g., oxalic acid) formation, cell growth, morphology, and general fungal performance is lacking.…”

Section: Discussionmentioning

confidence: 94%

GlaA Promoter Controlled Production of a Mutant Green Fluorescent Protein (S65T) by Recombinant Aspergillus niger during Growth on Defined Medium in Batch and Fed-Batch Cultures

et al. 1999

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The first successful expression of the Aequorea victoria green fluorescent protein (GFP) gene in Aspergillus niger is described. When the wild-type GFP gene was expressed in A. niger, neither the fluorescence nor the full translation product of the wtGFP gene was detectable. However, the expression of a mutant form of the green fluorescent protein (S65TGFP) gene resulted in the formation of a functional fluorescent polypeptide. The synthesis of S65TGFP was used to study glaA promoter controlled heterologous gene expression by recombinant A. niger in batch and fed-batch cultures using a defined growth medium. Cells were grown on xylose as noninducing carbon source, and the production of S65TGFP was accomplished by the addition of maltose. The recombinant protein accumulated up to 10 or 25 mg of S65TGFP g-1 cell dry weight using either a maltose pulse for induction or continuous addition of the inducing carbon source, respectively. Irrespective of the induction protocol, the recombinant protein started to accumulate 2 h after addition of the inducing carbon source and reached its maximum specific concentration 10 h after induction. Bright green fluorescing fungal pellets were first detectable by fluorescence microscopy 4-5 h after the onset of maltose addition.

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Section: Discussionmentioning

confidence: 94%

GlaA Promoter Controlled Production of a Mutant Green Fluorescent Protein (S65T) by Recombinant Aspergillus niger during Growth on Defined Medium in Batch and Fed-Batch Cultures

et al. 1999

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“…Support for a basal maintenance energy requirement is often derived from chemostat studies where the specific substrate consumption rate shows a linear dependency on , and the maintenance ration is defined by extrapolation to zero (17,46,56). However, some studies have documented deviations from the maintenance concept at low values in sporulating cultures (42,61). The specific growth rate observed in the maltose-limited retentostat cultures (0.005 h Ϫ1 Ͻ Ͻ 0.05 h Ϫ1 ) was below the range investigated in most chemostat-based studies.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, theory predicts that carbonand energy-limited retentostat cultures will approach a zero growth rate as the energy source consumed by the individual cell nears its maintenance ration (68). Previous studies of product formation in carbon-and energy-limited retentostat cultures of A. niger (60,61,69) have focused on products associated with vegetative growth, such as the major secreted glycoprotein glucoamylase and organic acids. It was also noted that A. niger was subject to differentiation as it approached a growth rate of zero (69).…”

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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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“…Before the advent of genomics techniques, retentostat cultivation was used to study microorganisms such as the bacteria Escherichia coli (30), Bacillus polymyxa (31), Paracoccus denitrificans, Bacillus licheniformis (28), Tetragenococcus halophila (32), Nitrosomonas europaea, and Nitrobacter winogradskyi (33) and the filamentous fungus Aspergillus niger (34)(35)(36)(37). More recently, the environmentally relevant bacteria Desulfotomaculum putei (38) and Geobacter metallireducens (39) …”

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confidence: 99%

Physiological and Transcriptional Responses of Different Industrial Microbes at Near-Zero Specific Growth Rates

Ercan

Bisschops

Overkamp

et al. 2015

Appl Environ Microbiol

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The current knowledge of the physiology and gene expression of industrially relevant microorganisms is largely based on laboratory studies under conditions of rapid growth and high metabolic activity. However, in natural ecosystems and industrial processes, microbes frequently encounter severe calorie restriction. As a consequence, microbial growth rates in such settings can be extremely slow and even approach zero. Furthermore, uncoupling microbial growth from product formation, while cellular integrity and activity are maintained, offers perspectives that are economically highly interesting. Retentostat cultures have been employed to investigate microbial physiology at (near-)zero growth rates. This minireview compares information from recent physiological and gene expression studies on retentostat cultures of the industrially relevant microorganisms Lactobacillus plantarum, Lactococcus lactis, Bacillus subtilis, Saccharomyces cerevisiae, and Aspergillus niger. Shared responses of these organisms to (near-)zero growth rates include increased stress tolerance and a downregulation of genes involved in protein synthesis. Other adaptations, such as changes in morphology and (secondary) metabolite production, were species specific. This comparison underlines the industrial and scientific significance of further research on microbial (near-)zero growth physiology. Most research in microbial physiology focuses on growing cells, although under natural and industrial conditions, microbes frequently encounter a state in which neither growth nor deterioration of cells occurs. However, the experimental design to study microbes in this clearly relevant physiological state is far from trivial.In this minireview, we define zero growth as a nongrowing state in which the viability and metabolic activity of a microbial culture are maintained for prolonged periods. As such, zero growth differs from starvation, which is coupled to cellular deterioration, loss of activity, and ultimately, cell death (1, 2). Zero growth also differs from differentiated survival states, such as bacterial or fungal spores, in which metabolism comes to a standstill (3). Conversely, under zero-growth conditions, microbes exclusively use available substrates for processes that contribute to maintenance of cellular integrity and homeostasis (4-7). Such processes include homeostasis of transmembrane gradients of protons and solutes, defense and repair systems, osmoregulation, and protein turnover (8, 9).In classical food fermentation processes, (near-)zero growth occurs during prolonged periods of extremely restricted availability of energy substrates. Examples include cheese ripening by lactic acid bacteria (LAB) (10-12), wine fermentation by Saccharomyces cerevisiae (13,14), and natto fermentation by Bacillus subtilis (15). Despite the severely energy-limiting conditions, microbes manage to survive in these processes for many weeks, while continuing to produce aroma and flavor compounds in the product matrix (10,13,15,16). Another incentive for studying...

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Organic Acid Production by Aspergillus niger in Recycling Culture Analyzed by Capillary Electrophoresis

Cited by 30 publications

References 0 publications

GlaA Promoter Controlled Production of a Mutant Green Fluorescent Protein (S65T) by Recombinant Aspergillus niger during Growth on Defined Medium in Batch and Fed-Batch Cultures

GlaA Promoter Controlled Production of a Mutant Green Fluorescent Protein (S65T) by Recombinant Aspergillus niger during Growth on Defined Medium in Batch and Fed-Batch Cultures

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

Physiological and Transcriptional Responses of Different Industrial Microbes at Near-Zero Specific Growth Rates

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