Physiological characterisation of recombinant Aspergillus nidulans strains with different creA genotypes expressing A. oryzae alpha-amylase.
The physiology of three strains of Aspergillus nidulans was examined--a creA deletion strain, a wild type creA genotype and a strain containing extra copies of the creA gene, all producing Aspergillus oryzae alpha-amylase. The strains were cultured in batch and continuous cultivations and the biomass formation and alpha-amylase production was characterised. Overexpression of the creA gene resulted in a lower maximum specific growth rate and a slightly higher repression of the alpha-amylase production during conditions with high glucose concentration. No expression of creA also resulted in a decreased maximum specific growth rate, but also in drastic changes in morphology. Furthermore, the expression of alpha-amylase was completely derepressed and creA thus seems to be the only regulatory protein responsible for glucose repression of alpha-amylase expression. The effect of different carbon sources on the alpha-amylase production in the creA deletion strain was investigated and it was found that starch was the best inducer. The degree of induction by starch increased almost linearly with the concentration of starch in starch/glucose mixtures. High-density batch cultivation was performed with the creA deletion strain and a final titre of 6.0 g l(-1) of alpha-amylase was reached after 162 h of cultivation.
Agger
Teit
T
Center for Process Biotechnology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Petersen
Jesper B
JB
O'Connor
Susan M
SM
Murphy
Rachael L
RL
Kelly
Joan M
JM
Nielsen
Jens
J
D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D001236:Aspergillus oryzae / Q000201:enzymology* / Q000235:genetics*; D018533:Biomass; D001709:Biotechnology; D004790:Enzyme Induction / Q000187:drug effects; D005656:Fungal Proteins / Q000235:genetics*; D017353:Gene Deletion; D020440:Gene Duplication; D015870:Gene Expression; D005800:Genes, Fungal; D005838:Genotype; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D011995:Recombination, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D013213:Starch / Q000494:pharmacology; D013379:Substrate Specificity; D000516:alpha-Amylases / Q000096:biosynthesis / Q000235:genetics*
D005656:Fungal Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; C071237:CreA protein, Aspergillus nidulans; D013213:Starch; D000516:alpha-Amylases