MINI-REVIEW Glucose oxidase: natural occurrence, function, properties and industrial applications Chun Ming Wong & Kwun Hei Wong & Xiao Dong Chen Received: 7 July 2007 / Revised: 8 February 2008 / Accepted: 8 February 2008 / Published online: 11 March 2008 # Springer-Verlag 2008 Abstract Glucose oxidase (GOX) from Aspergillus niger is a well-characterised glycoprotein consisting of two identical 80-kDa subunits with two FAD co-enzymes bound. Both the DNA sequence and protein structure at 1.9 Ǻ have been determined and reported previously. GOX catalyses the oxidation of D-glucose (C 6 H 12 O 6 ) to D-gluconolactone (C 6 H 10 O 6 ) and hydrogen peroxide. GOX is produced naturally in some fungi and insects where its catalytic product, hydrogen peroxide, acts as an anti-bacterial and anti-fungal agent. GOX is Generally Regarded As Safe, and GOX from A. niger is the basis of many industrial applications. GOX-catalysed reaction removes oxygen and generates hydrogen peroxide, a trait utilised in food preservation. GOX has also been used in baking, dry egg powder production, wine production, gluconic acid produc- tion, etc. Its electrochemical activity makes it an important component in glucose sensors and potentially in fuel cell applications. This paper will give a brief background on the natural occurrence, functions as well as the properties of glucose oxidase. A good coverage on the diverse uses of glucose oxidase in the industry is presented with a brief outline on the working principles in the various settings. Furthermore, food grade GOX preparations are relatively affordable and widely available; the readers may be encouraged to explore other potential uses of GOX. One example is that GOX-catalysed reaction generates significant amount of heat (∼200 kJ/mol), and this property has been mostly neglected in the various applications described so far. Keywords Glucose oxidase . Industrial applications . Aspergillus niger . Food processing . Additive . Enzyme . Properties . Occurrence . Functions Introduction Glucose-1-oxidase (GOX) (beta- D-glucose:oxygen-1- oxidoreductase, EC 1.1.3.4) is a well-characterised enzyme (Table 1), which catalyses the oxidation of beta-D-glucose (Eq. 1) to D-gluconolactone and hydrogen peroxide (Kleppet 1966; Wilson and Turner 1992). Both hydrogen peroxide (Eq. 2) and D-gluconolactone (Eq. 3) breaks down spontaneously and catalytically. Despite this, GOX’s enzymatic activity is reduced when hydrogen peroxide accumulates and inactivates the enzyme (Kleppet 1966); the breakdown product of D-gluconolactone, gluconic acid (C 6 H 12 O 7 ) accumulates, reducing pH of the solution. Not surprisingly, both gluconic acid (Miron et al. 2004) and hydrogen peroxide (Bao et al. 2001, 2003) can result in product inhibition of GOX. "‐D‐glucose þO 2 ! glucose oxidase D‐gluconolactone þ H 2 O 2 2H 2 O 2 ! spontaneous=catalase 2H 2 O þ O 2 ð2Þ D‐gluconolactone þH 2 O! spontaneous=lactonase gluconic acid Appl Microbiol Biotechnol (2008) 78:927–938 DOI 10.1007/s00253-008-1407-4 C. M. Wong (*) : X. D. Chen (*) Department of Chemical Engineering, Biotechnology & Food Engineering Group, Monash University, Melbourne, Victoria 3800, Australia e-mail: eric.wong@eng.monash.edu.au K. H. Wong P.O. Box 109175, Newmarket, Auckland 1149, New Zealand e-mail: dong.chen@eng.monash.edu.au (1) (3)