Sodium Gluconate Fermentation Process Improvement And The Comprehensive Utilization Of By-products

Sodium gluconate is a kind of mild organic acid Sodium salt with bitterness,non-poisonous,no-volatility and non-corrosiveness.The molecular formula of sodium gluconate is C₆H₁₁NaO₇ and its relative molecular weight is 218.14.It was soluble in water,slightly soluble in alcohol and insoluble.Sodium gluconate was widely used in chemical,food,medicine industry and light industry owing to its character of non-toxic,good thermal stability,no deliquescence,etc.There is four kinds of method producing sodium gluconate with glucose as the basic raw material: biological fermentation,homogeneous chemical oxidation,electrochemical oxidation,heterogeneous catalytic oxidation and enzyme catalysis,etc.The principle of biological fermentation is to use the Aspergillus Niger which secretion of glucose oxidase can cayalyze dehydrogenation oxidation of glucose to get grape acid lactone lactone and hydrogen peroxide,grape acid lactone further hydrolyzed to glucose acid,while hydrogen peroxide producted in the reaction can be Enzymatic hydrolysis into water and oxygen by hydrogen peroxidase which secreted by Aspergillus Niger.The glucose acid can be neutralized with a certain amount of sodium hydroxide solution which is flowed in the fermentation process to maintain a certain pH.The method of biological fermentation has become the most important industrial method beause of the superiority that the fermentation process is easy to control,product is easy to extract,reaction speed is fast,etc.In this paper,Aspergillus Niger is the strain which is produced sodium gluconate,the fermentation process has been optimized and shortten the fermentation period.The residual sugar was qualitative appraisal and further studied the reasons caused and find out strategy reducing residul sugar.The fermentation by-product-mycelium contains abundant glucose oxidase,studied the use of waste bacteria production technology contain abundant of glucose oxidase and can be comprehensive utilized to extract enzyme.（1）To shortten fermentation period of sodium gluconate,different inoculation way,inoculation quantity and seed culture time had been employed to optimized fermentation process.The optimal culture condition for producing sodium gluconate were obtained（10% inoculation quantity,seed culture time is 20h）.At the end of fermentation,the glucose consumption rate,bacteria and glucose oxidase activity in the fermentation broth were streanth.So flowing plus glucose solution was adoptted to using high active bacteria to lower the cost of production.（2）The glucose could not be detected by biological sensor after the fermentation,while the Reducing sugar still be detected in the fermentation broth by fehling reagent.The residual sugar has been isolated and purified from the process of decoloring,enrichment crystallization,centrifugal separation and ion exchange treatment.It was concluded that the major component of residual sugar is fructose by paper chromatography and high performance liquid chromatography（HPLC）detection,and and the fructose was from enol type conversion that caused by too high concentation sodium hydroxide in the fermentation liquid.The residual sugar content dropped to 0.1% from 0.66% by changing the flow way of sodium hydroxide liquid.（3）To get optimum stratage extrating glucose oxidase from mycelium,four kinds of method of cell disruption（mechanicalattrition,ultrasonic method,high-speed homogenization and repeated freeze-thaw method）has been employed,and find the method of mechanicalattrition is the most efficient way to extract the crude enzyme liquid of glucose oxidase by comporation.To get optimum efficiency of precipitate glucose oxidase,different saturation of ammonium sulfate precipitation effect of glucose oxidase.The glucose oxidase has been purified by Sephadex G-25 column chromatography desalination,DEAE cellulose 32-ion chromatography and Sephadex G-100 molecular sieve chromatography.The protein liquid has been identified by PAGE electrophoresis,and only get single electrophoresis band in the end.A technological process extracting glucose oxidase by using sodium gluconate waste bacteria has been set up.