Effect of oxygen enrichment on morphology, growth, and heterologous protein production in chemostat cultures of Aspergillus niger B1-D

✍ Scribed by Aporn Wongwicharn; Brian McNeil; Linda M. Harvey

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 202 KB
• Volume: 65
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/(sici)1097-0290(19991120)65:4<416::aid-bit6>3.0.co;2-z

✦ Synopsis

The response of steady state chemostat cultures of a recombinant Aspergillus niger (B1-D), secreting both a heterologous enzyme (Hen Egg White Lysozyme [HEWL]) and a native enzyme (Glucoamylase), to varying levels of O 2 enrichment of the process gas was evaluated. Formation of both the native and the foreign enzyme increased with increasing O 2 supply. Conversely, biomass levels and total extracellular protein levels were generally not increased under O 2 enriched conditions. Two distinct micromorphologies were apparent in these cultures, one, typically seen under O 2 limiting conditions (i. e. at 0 and 10% enrichment levels), tended to be represented by long, sparsely branched hyphal elements, with low percentages of "active" length (i. e. how much of the hypha is cytoplasm filled); whilst, a second micromorphology, typical of O 2 enriched cultures at 30 and 50% O 2 enrichment, was represented by shorter hyphal elements, with more branching and a higher % "active" length. At these higher O 2 levels, formation of a yellow pigment occurred, and signs of culture autolysis were noted. At 50% enrichment, a "stranded" aggregate morphology was apparent, possibly as a response to a hyperoxidant state. Production of both the native enzyme and HEWL correlated well with a simple morphological measure (tip number) or, with % "active" length. It is proposed the morphological changes noted in the cultures were associated with the increased production of both HEWL and glucoamylase.