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.

Wikipedia

Citric Acid Production by Aerobic Bioprocesses

- 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 Citric Acid

Industrial Production of Ethanol

Application of Ethanol:

- Medical

- Fuel

- Industrial

Ethanol Production by Anaerobic Bioprocesses

Glycolysis

- Microorganism: S. cerevisae for hexoseCandida sp. for lactose or pentoseGenetically 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 reactor21 h in continuous reactor without cell recycle1.6 h in continuous reactor with cell cycle

By-products: glycerol, acetic acid, succinic acid.

Industrial Production of Citric 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

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