Glucose oxidase induction and the modelling of gluconic acid production using Aspergillus niger

• Main Author: Johnson, Kim Henry Silvanus
• Other Authors: Harrison, STL
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2016
• Subjects: Bioprocess Engineering
• Online Access: http://hdl.handle.net/11427/21517

The aim of this project is to establish and understand the production of glucose oxidase and gluconic acid using the Aspergillus niger bioprocess and predict its response to operating conditions. Glucose oxidase and gluconic acid are produced by a wide range of microbes and have a variety of applications. In this study Aspergillus niger was chosen as the microorganism as it has the "generally accepted as safe" (gras) status in the U.S.A. It is also the major industrial producer. Glucose oxidase catalyses the conversion of glucose, oxygen and water to hydrogen peroxide and gluconic acid. This enzyme is used as a glucose and oxygen scavenger in the food industry and as a diagnostic tool in medicine for glucose determination. Gluconic acid is an organic acid used as a sequestering agent with a broad spectrum of applications. The world market for gluconic acid and its various salts was 45 000 metric tonnes in 1985 (Bigelis cited by Markwell et al. 1989). Gluconic acid and its derivatives can be produced using three technologies: electrolysis, mild chemical oxidation and bioprocess. The first two technologies have not been proven to be comnercially viable. The bioprocess offers diversity of feed and produces other products such as glucose oxidase. Literature has shown that the production of gluconic acid involves two kinetic areas. Firstly, the glucose oxidase enzyme must be induced. Secondly, glucose is converted to gluconic acid by the enzyme glucose oxidase. The factors affecting the kinetics associated with the induction of glucose oxidase have only been described qualitatively. Glucose, oxygen and pH have been shown to affect the induction of glucose oxidase. The effect of pH has been studied by Roukas and Harvey (1989) who found that induction, is maximal at a pH of between 5 and 6. The effect of glucose and oxygen have not been quantified. The kinetics of glucose oxidase conversion of glucose to gluconic acid have been well described by Atkinson and Lester (1974).