Industrial Production of Citric Acid Application of Citric Acid: (text,p.524) - Acidulant in food, confectionary, and beverage (75%) - Pharmaceutical (10%), e.g. soluble aspirin preparation - industrial (15%): complexes with metals such as iron and copper to be stabilizer of oil and fats. Citric Acid Production by Aerobic Bioprocesses Wikipedia Industrial Production of Citric Acid - Microorganism: Aspergillus niger (mainly), Candida yeast (from carbohydrates or n-alkanes) - Citric acid production is mixed growth associated, mainly take place under nitrogen and phosphate limitation after growth has ceased. - Medium requirements for high production - Carbon source: molasses or sugar solution. - Na-ferrocyanide is added to reduce Iron (1.3 ppm) and manganese (<0.1ppm). - High dissolved oxygen concentration - High sugar concentration - pH<2 - 30 oC. Industrial Production of Citric Acid Bioreactor: batch or fed-batch (100m3) - 5-25X106 A. niger spores/L may be introduced to the fermentor. - Aeration is provided to the fermenter by air sparging (0.1-0.4 vvm) - Temperature is controlled by cooling coil. - Agitation: 50-100rpm to avoid shear damage on molds. - Fed-batch is used to reduce substrate inhibition and prolong the production phase one or two days after growth cessation. - Volumetric yield: 130 kg/m3 Industrial Production of Citric Acid Separation: - The biomass is separated by filtration - The liquid is transferred to recovery process: - Separation of citric acid from the liquid: precipitation calcium hydroxide is added to obtain calcium citrate tetrahydrate → wash the precipitate→ dissolve it with dilute sulfuric acid, yield citric acid and calcium sulfate precipitate → bleach and crystallization → anhydrous or monohydrate citric acid. Industrial Production of Ethanol Application of Ethanol: - Medical - Fuel - Industrial Ethanol Production by Anaerobic Bioprocesses Glycolysis Industrial Production of Citric Acid - Microorganism: S. cerevisae for hexose Candida sp. for lactose or pentose Genetically modified E. coli - Ethanol production is growth-associated with S. cerevisae. - Medium requirements for high production - Carbon source: sugar cane, starch materials (e.g. corn, wheat), cellulosic materials (?!). yield: 0.51 g ethanol/g glucose. - N, P, minerals. - Anaerobic - 100g/L glucose are inhibitory for yeast. - 5% (v/v) of ethanol are inhibitory for yeast. - pH:4-6 for 30-35 oC. Industrial Production of Citric Acid Bioreactor: batch, continuous or with cell recycle 95% conversion of sugars with a residence time of 40 h in batch reactor 21 h in continuous reactor without cell recycle 1.6 h in continuous reactor with cell cycle By-products: glycerol, acetic acid, succinic acid. Separation: - Distillation to obtaining 95% (w/w) of ethanol-water mixture, followed by - Molecular sieves to removing water from the mixture to get anhydrous ethanol. Ethanol Production http://www.cleantechblog.com/uploaded_images/production_process-718492.jpg