Effect of dimorphic regulation on heterologous glucose oxidase production by Mucor circinelloides

Abstract

The production of Aspergillus niger glucose oxidase (GOX) and native amylase by the recombinant M. circinelloides KFA199 strain under conditions of dimorphic growth was investigated. The recombinant KFA199 strain was compared to its parental ATCC 1216b strain and a wild-type CBS 232.29 strain under similar morphology-controlled conditions. Cultivation in Vogel's medium supplemented with ergosterol/Tween-80 and sparged with nitrogen gas was most suitable for yeast-like biomass production under anaerobic conditions. Anaerobic growth was characterized by high levels of ethanol formation and linear growth rates of 0.24-0.05/h, indicating metabolic stress. Subsequent to anaerobic growth, cultures were shifted to aerobic conditions to induce aerobic mycelial growth. GOX produced by the recombinant KFA199 after the shift to aerobic conditions was poorly secreted and accumulated intracellularly to 0.56 U/ml(culture). Amylase production by the KFA199, ATCC12b and CBS 232.29 strains was determined during growth on starch after the shift to aerobic culture. Growth-associated amylase production by the ATCC 1216b (0.63 U/ml(culture)) and wild-type CBS 232.29 (0.33 U/ml(culture)) strains was substantially higher than by the recombinant KFA199 strain (0.07 U/ml(culture)), which may be related to the leucine auxotrophy of the transformation host, or genetic changes induced during transformation of the KFA199 strain.