title: Growth behaviour and glucoamylase production by Aspergillus niger N402 and a glucoamylase overproducing transformant in recycling culture without a nitrogen source.
abstract: When wild-type Aspergillus niger N402 and a glucoamylase-overproducing transformant were grown in recycling culture without a nitrogen source, hyphal tip extension and glucoamylase production still occurred, but overproduction of glucoamylase by the transformant strain stopped. The mycelium retained a low metabolic activity. Light micrographs of mycelial samples showed that some hyphae were broken at their tip and partially empty, while after continuing recycling fermentation for more than 500 h many small and empty pieces of broken mycelium could be found. A model has been developed to calculate the mycelial growth and death rates. The mycelial death rate just exceeded the mycelial growth rate and as a consequence the amount of biomass in the fermentor vessel slightly decreased. It is concluded that the cytoplasmic contents of broken mycelial threads were released into the medium and acted as a nitrogen source for the growing parts of the mycelium.
authors.affiliation: Department of Microbiology, Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Schrickx
authors.forename: A H
authors.initials: AH
authors.lastname: Stouthamer
authors.forename: H W
authors.initials: HW
authors.lastname: van Verseveld
mesh_terms: D001234:Aspergillus niger / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D005087:Glucan 1,4-alpha-Glucosidase / Q000096:biosynthesis*; D009584:Nitrogen / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: D005087:Glucan 1,4-alpha-Glucosidase; D009584:Nitrogen