Use of a series of chemostat cultures to isolate 'improved' variants of the Quorne myco-protein fungus, Fusarium graminearum A3/5

Abstract

Variants (designated A23-S and A24-S) of the QuornB myco-protein fungus, Fusarium graminearurn A3/5 were isolated from a series of glucose-limited cultures grown at a dilution rate of 0.18 h-I for a combined total of 109 d. These variants had unchanged mycelial morphologies but, when grown in mixed culture with the parental strain (A3/5) in glucose-limited chemostat culture at 018 h-l, A234 and A24-S had selection coefficients of 0.013 and 0017 h-l, respectively, and supplanted A3/5. When a monoculture of A23-S was grown in a glucose-limited culture at a dilution rate of 0-18 h-l, the appearance of highly branched (so-called colonial) mutants was delayed compared with their appearance in chemostat cultures of the parental strain. Furthermore, when a monoculture of A24-S was grown in glucose-limited culture at 0 1 8 h-l, the appearance of colonial mutants was delayed even further. Thus, it is possible to isolate advantageous (relative to A3/5) variants of F. graminearum A3/5 which have unchanged mycelial morphologies, but in which the appearance of colonial mutants is delayed.

Recombinant Glucoamylase Production byAspergillus nigerB1 in Chemostat and pH Auxostat Cultures

“…The concentration of each strain was determined as described in Wiebe et al (1994). Measurement of biomass and glucose concentrations.…”

Isolation of a fluffy mutant of Aspergillus niger from chemostat culture and its potential use as a morphologically stable host for protein production

“…Chemostat cultivation is mainly used for determining process variables and for characterizing strains at different specific growth rates. A major problem in the use of continuous cultures is the rapid appearance of morphological mutants, often leading to a reduction in protein production and altered growth characteristics (Christensen et al, 1995;Mainwaring et al, 1999;Wiebe et al, 1994;Withers et al, 1998). The mutants were affected in sporulation, branching, or both Wiebe et al, 1993;Withers et al, 1995) and were often demonstrated to have a selective advantage over the parental strain.…”

“…Losing some of these copies is advantageous for the organism, but reduces the desired protein production (Christensen et al, 1995;Mainwaring et al, 1999;Swift et al, 1998). Wiebe et al (1994) have isolated stable ''variants'' of Fusarium graminearum from a chemostat culture. These variants had a selective advantage over their parent and were morphologically more stable in chemostat cultures.…”

Evolution of a recombinant (gucoamylase‐producing) strain of Fusarium venenatum A3/5 in chemostat culture

“…1). Southern Simpson et al, 1995;Wiebe et al, , 1992bWiebe et al, , 1993Wiebe et al, , 1994 analysis demonstrated that all of these mutants possessed the amdS gene, although all had lost some copies of the gene (Fig. 2).…”

“…Morphological mutants of F. venenatum JeRS 325 were isolated from glucose-limited chemostat cultures as described by Wiebe et al ( , 1994. Mutants were named according to the fermentation from which they were isolated (e.g., T2 or T21) followed by a descriptive letter (C ‫ס‬ colonial, S ‫ס‬ sparse, A ‫ס‬ altered aerial hyphae) and a number to distinguish it from other mutants isolated from the same fermentation.…”