Morphology and physiology of an α-amylase producing strain of Aspergillus oryzae during batch cultivations

Carlsen, Morten; Spohr, Anders Bendsen; Nielsen, Jens; Villadsen, John

doi:10.1002/(sici)1097-0290(19960205)49:3<266::aid-bit4>3.0.co;2-i

Cited by 149 publications

(68 citation statements)

References 28 publications

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“…This pathway enables A. oryzae to produce large amounts of malic acid uncoupled from growth, which makes it a very interesting trait for future industrial applications. From an ecological and evolutionary point of view, direct glucose conversion to malic acid makes sense, as (i) glucose consumption can continue, reducing the availability for competing microorganisms, like many fast-growing bacteria; (ii) microbial growth is oppressed by low pH, whereas aspergilli are tolerant to acidic pHs (A. oryzae, for example, shows optimal growth over a broad pH range from 3 to 7 [31]); and (iii) sequence analysis of A. oryzae showed that it has the largest expansion of secretory hydrolytic enzymes that work at low pH, in comparison to the expansion for A. nidulans and A. fumigatus (12). This might help the cell to survive in an environment with only complex nitrogen sources available.…”

Section: Discussionmentioning

confidence: 99%

Investigation of Malic Acid Production in Aspergillus oryzae under Nitrogen Starvation Conditions

Knuf

Nookaew

Brown

et al. 2013

Appl Environ Microbiol

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bMalic acid has great potential for replacing petrochemical building blocks in the future. For this application, high yields, rates, and titers are essential in order to sustain a viable biotechnological production process. Natural high-capacity malic acid producers like the malic acid producer Aspergillus flavus have so far been disqualified because of special growth requirements or the production of mycotoxins. As A. oryzae is a very close relative or even an ecotype of A. flavus, it is likely that its high malic acid production capabilities with a generally regarded as safe (GRAS) status may be combined with already existing large-scale fermentation experience. In order to verify the malic acid production potential, two wild-type strains, NRRL3485 and NRRL3488, were compared in shake flasks. As NRRL3488 showed a volumetric production rate twice as high as that of NRRL3485, this strain was selected for further investigation of the influence of two different nitrogen sources on malic acid secretion. The cultivation in lab-scale fermentors resulted in a higher final titer, 30.27 ؎ 1.05 g liter ؊1 , using peptone than the one of 22.27 ؎ 0.46 g liter ؊1 obtained when ammonium was used. Through transcriptome analysis, a binding site similar to the one of the Saccharomyces cerevisiae yeast transcription factor Msn2/4 was identified in the upstream regions of glycolytic genes and the cytosolic malic acid production pathway from pyruvate via oxaloacetate to malate, which suggests that malic acid production is a stress response. Furthermore, the pyruvate carboxylase reaction was identified as a target for metabolic engineering, after it was confirmed to be transcriptionally regulated through the correlation of intracellular fluxes and transcriptional changes.

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Section: Discussionmentioning

confidence: 99%

Investigation of Malic Acid Production in Aspergillus oryzae under Nitrogen Starvation Conditions

Knuf

Nookaew

Brown

et al. 2013

Appl Environ Microbiol

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“…The morphology of Aspergillus, filamentous growth forms and/or the shape and size of pelleted growth forms as well as the branching frequency, is influenced by many factors including specific strain properties [22] but also environmental factors such as spore numbers in the inoculum or type of inoculum [23][24][25], medium composition [23,[26][27][28], dissolved oxygen concentration [29][30][31], pH [23,32], temperature [23,27], reactor type and scale [27,33], and power input [23,25,26,28,29,[33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

El‐Enshasy

Kleine

Rinas

2006

Process Biochemistry

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Recombinant Aspergillus niger genetically engineered to produce glucose oxidase using the constitutive gpdA promoter and the glucoamylase signal sequence for secretion was grown in batch cultures at agitation speeds of 200 -800 rpm covering the industrial relevant power input range of 0.1 -5 W kg -1 . The growth morphology ranged from large pellets with an average diameter of 1500 µm at low power input up to micropellets embedded in a filamentous network at high power input. A correlation of agitation intensity with growth morphology and glucose oxidase production revealed an increase of the protein production capability with the change of the growth morphology from pelleted to filamentous growth forms. However, the exposure to higher shear stress with increasing power input also resulted in lower biomass yields as well as increased transient formation of polyol (xylitol) and higher final concentrations of oxalic acid. The highest specific production rates were found in young filamentous growth forms at high power input. Although intermediate agitation intensity leading to small pellets became more favorable during prolonged cultivation. An acridine orange staining procedure discriminating between RNA rich (red) and RNA poor regions (green) of the fungal biomass proved that active protein production is restricted to filamentous growth forms and the outer layer of fungal pellets. A correlation between the RNA rich fraction of the biomass determined by image analysis and the productivity is shown.

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“…Batch cultures were carried out in an inhouse 5-liter glass fermentor as described previously (3,11); under these conditions, ␣-amylase synthesis is strongly induced. ␣-Amylase activity was determined using an Amyl kit (Boehringer Mannheim GmbH, Mannheim, Germany) in a Cobas Mira analyzer (F. Hoffman-La Roche Ltd., Basel, Switzerland).…”

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confidence: 99%

Antisense Silencing of the creA Gene in Aspergillus nidulans

Bautista

Aleksenko

Hentzer

et al. 2000

Appl Environ Microbiol

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Antisense expression of a portion of the gene encoding the major carbon catabolite repressor CREA in Aspergillus nidulans resulted in a substantial increase in the levels of glucose-repressible enzymes, both endogenous and heterologous, in the presence of glucose. The derepression effect was approximately one-half of that achieved in a null creA mutant. Unlike results for that mutant, however, growth parameters and colony morphology in the antisense transformants were not affected.

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Morphology and physiology of an α-amylase producing strain of Aspergillus oryzae during batch cultivations

Cited by 149 publications

References 28 publications

Investigation of Malic Acid Production in Aspergillus oryzae under Nitrogen Starvation Conditions

Investigation of Malic Acid Production in Aspergillus oryzae under Nitrogen Starvation Conditions

Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

Antisense Silencing of the creA Gene in Aspergillus nidulans

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