The Synthesis Of Gluconate By Glucose Oxidase And Catalase

As one of the most important chemical products, gluconic acid and gluconate had been widely used in chemistry, food products, pharmaceutical and other industries. The preparation methods of gluconic acid including chemical catalysis, biological fermentation and enzyme catalysis. The heavy metal was used to synthesize gluconic acid in chemical catalysis, and long fermentation cycle and multiple by-product for biological fermentation limited the methods applications. The property of mild reaction conditions, easy separation of production and high purity of product for enzyme catalysis attracts many researchers'attention. However, free enzymes can only be used one time, thus the high cost of enzyme became the limiting factor for producing gluconic acid. In this work, the conditions of synthesizing gluconic acid were tested. The method aimed for reducing enzyme cost and enhancing enzyme stability and catalytic efficiency were explored. The main contents were as following:1. GOD and CAT were co-immobilized for synthesizing gluconic acid. The choice of the immobilized support, enzyme loading amount and the immobilized conditions were optimized. The optimal support was D301, the ratios of GOD:CAT was 5:1 (v/v), and the crosslinked time was 2 h. The immobilized GOD activity was increased 20% when the support was pretreated with NaOH. The glucose was 100% conversed to gluconic acid with the immobilized enzyme in a 300 L bio-reactor.2. The biological cross-linker were used to improve enzyme stability and glucose conversion. After optimizing the cross-linker types and the crosslinked conditions. Transglutaminase (TG) was selected as the suitable crosslinker.0.05 g TG,0.2 ml CAT and 8.8ml water were mixted then 0.1 g gelatin was added to the solution, after that 1ml GOD was added to the system, crosslinking 3 h at 30?, GOD activity in crosslinked enzyme was increased 30%. The conversion of glucose with crosslinked enzyme was 10% higher than that with free enzymes when the glucose concentration was 15%(w/v). The GOD stability and thermo-stability were enhanced, the activity maintained 57.8% when the crosslinked enzymes were in 60 ? for 36 h, however, the activity only residue 15% with free enzymes.3. The reaction parameters were regulated when synthesizing gluconic acid. The optimum pH value was 5.00, when pH was controlled at 5.00 the glucose conversion was 20% higher than that without pH control. The additional of hydrogen peroxide can improve the dissolved oxygen efficiently. When the glucose concentration was 30%, the glucose could be completely conversed after 12 h with the controlled conditions.