TY - JOUR

T1 - Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

AU - El-Enshasy, Hesham

AU - Kleine, Joachim

AU - Rinas, Ursula

N1 - Funding Information: H. El-Enshasy wishes to thank the DAAD, Germany for financial support. We gratefully acknowledge critical reading of the manuscript by Xin Lu. Part of this study was carried out in the framework of the Sonderforschungsbereich 578 (Project B1/B4).

PY - 2006/10

Y1 - 2006/10

N2 - 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.

AB - 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.

KW - Agitation

KW - Glucose oxidase

KW - Morphology

KW - Protein excretion

KW - Recombinant Aspergillus niger

UR - http://www.scopus.com/inward/record.url?scp=33748520515&partnerID=8YFLogxK

U2 - 10.1016/j.procbio.2006.05.024

DO - 10.1016/j.procbio.2006.05.024

M3 - Article

AN - SCOPUS:33748520515

VL - 41

SP - 2103

EP - 2112

JO - Process biochemistry

JF - Process biochemistry

SN - 1359-5113

IS - 10

ER -