"Things You May Not Know about Glucose Oxidase"

For some of us, the word enzyme is not a never-heard-before word. Enzyme is a macromolecule that is able to catalyze a biochemical reaction. It has a lot of functions and is related to our human body. However, enzyme is not only used in the process that is occurring in our body system. It is used in industries as well, such as in baking, dairy, winery, brewing, or meat industries. 

Certain enzymes are applied to make the desired characteristics. These enzymes are added because without them, the qualities of the product may not be good enough. Customers tend to have their own criteria when choosing products that they want to buy. Some of these enzymes are added to satisfy customers' needs.

In this article, enzyme called glucose oxidase will be explained further. Glucose oxidase has been used successfully to remove residual glucose and oxygen in foods and beverages aiming to increase their shelf life. Also known as the acronym GOX/GOD, this enzyme is used in the baking industries. Glucose oxidase is an enzyme that can be used to promote the oxidation of the protein matrix and is attracting considerable interest as a wheat-flour dough improver (Dunnewindet al., 2002).GOD catalyzes the oxidation of -D-glucose into D-glucono--lactone at its first hydroxyl group using atomic oxygen (O2) as the electron acceptor with the synchronous generation of hydrogen peroxide (H2O2). Both end products break down spontaneously and catalytically (Lezkovac et al., 2005).  

Image from: researchgate.net

In the baking industry, calcium peroxide has been used for many years as an effective oxidant for breads production, mainly in the US. The active ingredient is H2O2that is produced by CaO2. However, CaO2has limited solubility in water. Therefore, CaO2is always dry blended with flour in commercial usages. As an alternative for CaO2, glucose oxidase is used since it also produces H2O2. 

The enzyme acts on -D-glucose and, in the presence of O2, produces D-gluconic acid and also H2O2. FAO/WHO and GRAS requirements claim that glucose oxidase qualifies all the requirements to be considered food-grade enzymes. In addition, it is soluble in water and has been reported to be stable for at least one year when stored at 2-4ºC. 

Glucose oxidase mainly produced by the mycelial fungi such as Aspergillusand Penicilliumespecially in industrial area (Singh and Verma, 2013). The organisms are Penicillium notatum, Penicillium chrysosporium, Aspergillus niger, and Botrytis cinerea(Hafiz et al., 2013). The one that is produced from Aspergillus niger GODis homodimeric and is a secreted protein intracellular enzyme that is present in the mycelium of the organisms (Willis, 1966 cited by Hafiz et al., 2003). An elaboration is made between the simple extraction step of the mycelial mass, cation exchange chromatography, and gel filtration to receive a pure fungal glucose oxidase enzyme particularly from Aspergilli andPenicillia. Moreover, glucose oxidase is optimum in pH 4.5 and in temperature of 40 to 50C (Toyobo Enzymes, n.d.).

Every enzyme has an EC (Enzyme Commission) number, and glucose oxidase's EC is 1.1.3.4. The number is based on the class, subclass, and sub-sub class of the enzyme classification. The first number, 1, represents the class of the enzyme, which is oxidoreductase. Just like the name, this class of enzyme catalyzes oxidoreduction reactions. The oxidized substrate is regarded as a hydrogen donor. The systematic name is based on the donor:acceptor oxidoreductase. The recommended name will be dehydrogenase. Reductase can be used as an alternative as well. Oxidase is only used in cases where the acceptor is oxygen. The EC 1.1 means that it acts on the CH-OH group donos, and the category EC 1.1.3. refers to oxygen as the acceptor. 

The previous paragraphs have mentioned about hydrogen peroxide (H2O2) that is highly attributed in shaping the dough properties by glucose oxidase. Hydrogen peroxide causes the oxidation of free groups of sulfhydryl in gluten proteins that leads to the disulfide linkages formation. The amount and the rate of hydrogen peroxide production determines the extent of cross-linking. 

High levels of hydrogen peroxide (especially during the mixing phase) may decrease the size of the gluten aggregates formed rather than the formation of an extended gluten network. If mechanical shear is applied during the dough mixing, some of the newly-formed disulfide bridges may be broken, thus leaving fewer SH groups to form linkages at the next stages. 

This will be less effective in stabilizing the dough structure than the gluten aggregates formed when the hydrogen peroxide is present at lower levels. (Decamps et al., 2014). The hydrogen peroxide production takes place in a controlled condition where over-oxidized gluten network is avoided. A more extensive and probably larger gluten network is formed and hence improving the overall strength of the gluten network. It allows the dough to be more elastic and able to be stable when it is stretched. 

Furthermore, GOD (Glucose Oxidase) is extremely in particular for the -anomer of D-glucose, while the -anomer does not seem, by all accounts, to be a reasonable substrate (Bankar et al., 2009). Thus, glucose oxidase brings down activities while using 2-deoxy-D-glucose, D-mannose, and D-galactose as substrates. In consequence, among other enzymes presently known to oxidize glucose; glucose oxidase is the best-known because of its high degree of specificity (Dubey et al., 2017). 

References:

Bankar, S.B, et al.2009. Glucose oxidase---an overview. Biotechnol Adv. 27(4): 489-501.

Decamps, K, et al.2014. Impacr of pyranose oxidase from Trametes multicolor, glucose oxidase from Aspergillus niger and hydrogen peroxide on protein agglomeration in wheat flour gluten starch separation. J. Food Chem., 148:235-239.

Dunnewind, B. et al. 2002. Effect of oxidative enzymes on bulk rheological properties of wheat flour doughs. Journal of Cereal Science, 36:357-366.

Duber, M.K., et al. 2017. Improvement strategies, cost effective production, and potential application of Fungal Glucose Oxidase (FOD): Current updates. Front Microbiol. 8:1032. 

Hafiz, M., M. Hamid, Khalil--ur--Rehman, Anjum Zia and M. Asgher, 2003. Optimization of Various Parameters for the Production of Glucose Oxidase from Rice Polishing Using Aspergillus niger. Biotechnology, 2: 1-7.

Leskovac, V., et al. 2005. Glucose oxidase from Aspergillus niger: the mechanism of action with molecular oxygen, quinones, and one-electron acceptors. Int. J. Biochem Cell Biol. 37(4):731-750.

Singh, J. and N. Verma 2013. Glucose oxidase from Aspergillus niger: Production, characterization and immobilization for glucose. Advances in Applied Science Research 4(3):250-257.

Toyobo Enzymes, n.d., Glucose oxidas from Aspergillus sp.[online] Retrieved from:<http://www.toyoboglobal.com/seihin/xr/enzyme/pdf_files/113_116GLO_201.pdf> [accessed on October 3, 2018].

Dibuat oleh: Cho Jin Joo Vanessa (02320171008); Florencia Belinda Nathania (02320171016); Clarissa Auliani (02320171018)