OPTIMIZATION OF GLUCOSE-OXIDASE PRODUCTION BY ASPERGILLUS-NIGER USINGGENETIC AND PROCESS-ENGINEERING TECHNIQUES

Wild-type Aspergillus niger NRRL-3 was transformed with multiple copie s of the glucose oxidase structural gene (god). The gene was placed un der the control of the gpdA promoter of A. nidulans. For more efficien t secretion the alpha-amylase signal peptide from A. oryzae was insert ed in front of god. Compared to the wild type, the recombinant strain NRRL-3 (GOD3-18) produced up to four times more extracellular glucose oxidase under identical culture conditions. Addition of yeast extract (2 gl(-1)) to a mineral salts medium containing only glucose as carbon source increased volumetric and specific extracellular glucose oxidas e activities by 130% and 50% respectively. With the same medium compos ition and inoculum size, volumetric and specific extracellular glucose oxidase activities increased more than ten times in bioreactor cultiv ations compared to shake-flask cultures.