1-Citric acid
Carbon source pretreatment
Metal salts and phosphate concentration in the medium were found to influence the yield.
For this reason, the carbon source must be re treated with either precipitation or exchanger to remove cations
The use of methanol:
Render the mycelium not sensitive to the presence of iron in the medium.
Phases of fermentation
The first phase the conditions should be adjusted for maximum growth to obtain enough mycelium
The second phase the conditions is shifted to restriction of cationsto enhance the production of citric acid
Optimum production is achieved at low pH (3.5).
The low pH have the advantage of lowering the risk of contamination.
1-Citric acid
1-Citric acidSubmerged culture process Surface fermentation processThe aeration rate should be optimized during citric acid production as fungus require little oxygen in the same time it is sensitive to oxygen deficiency
The structure of the mycelium produced during the trophophase(logarithmic phase of growth) is very important for citric acid yieldVery small Solid pellets gives high yield
Loose, filamentaousmycelium with limited branches gives low yieldIncubated at 28°CThe process usually takes from 5-8 days
The structure of the mycelium produced during the trophophase(logarithmic phase of growth) is very important for citric acid yieldVery small Solid pellets gives high yield
Loose, filamentaousmycelium with limited branches gives low yieldIncubated at 28°CThe process usually takes from 5-8 days
1-Citric acidSubmerged culture process Surface fermentation processRecovery :•Oxalic acid is removed first by pptas calcium oxalate at low PH then removed by centrifugation together with the fungal mycelia•Citric acid is then pptas calcium citrate at PH (7.2) and 70-90°C, the pptis then filtered, dried or subjected to further purification if requiredAdvantageSterilization is easily controlled
Higher yield
Organism is in contact with nutritive medium therefore high yield is obtainedRecovery : The produced citric acid is extracted with hot water then purified
Advantages :
Simple
Needs low investment-
Sterilization is not easily controlled ( high risk of contamination)Disadvantage :High labor cost
Higher yield
Organism is in contact with nutritive medium therefore high yield is obtainedRecovery : The produced citric acid is extracted with hot water then purified
Advantages :
Simple
Needs low investment-
Sterilization is not easily controlled ( high risk of contamination)Disadvantage :High labor cost
2-Gluconicacid
Importance1. Used in metal and leather industries.2. Used source of calcium for the body in the form of calcium gluconate.3.Used as ferrous gluconatefor treatment of anemia.
2-Gluconicacid
nigerAspergillsorganism used: -Micro)Submerged culture(Method used: during which all the amount of 48 hrs -36The process take about the glucose is utilized (carbon source).results in the utilization of the produced Further incubationgluconicacid.The fermentation is conducted under highly aerobic conditions –PH is controlled at 5.5 by using calcium carbonate –temp. is kept at 30°C.0.1% boron (borate salt) is added to the fermentation medium to stabilize the calcium gluconateand prevent it's ppt(which have low solubility).
2-Gluconicacid
Recovery: Fungal mycelia are removed by centrifugation. Calcium hydroxide is added to the fermentation broth to pptcalcium gluconateThen free acid is recovered from the crystalline ca-gluconateby addition of acid.
3. Lactic acid
Importance:
1.Calcium lactate is used in the treatment of calcium deficiency
2.Iron lactate is used in treatment of anemia.
M.O used:Lactobacillus delbrueckiis used for production
Method used : submerged culture:
Lactic acid fermentation is carried out under anaerobic or microaerophilicconditions at temperature range of 40-500C and pH range of 5.5-6.5.
Calcium hydroxide is added to the fermentation broth to control the pH.
The fermenteris agitated for mixing but not aerated.
Fermentation usually takes about 2-3 days.
Recovery:
the fermentation mesh is boiled to coagulate the microbial proteins which is trapped on a filter and dried for use as animal feed supplement.
The filtrate, which contains the soluble calcium lactate, is concentrated by using a vacuum then subjected to further purification.