Production of lactic acid and fungal diastage by fermentation

Lactic acid and fungal diastase are both produced through fermentation processes, though the methods, organisms involved, and end products differ. Below is a description of the production of each.

 

Production of Lactic Acid by Fermentation

1. Microorganisms: Lactic acid is produced via lactic acid bacteria (LAB) such as Lactobacillus, Streptococcus, Pediococcus, and Leuconostoc. These bacteria are capable of fermenting sugars into lactic acid.

2. Fermentation Substrates: The primary substrates used are carbohydrates, particularly glucose, sucrose, or lactose, which are broken down into lactic acid. Common sources include:

   • Corn starch
   • Molasses
   • Whey (a byproduct of cheese production)

3. Anaerobic Fermentation: The process is typically anaerobic (without oxygen). The bacteria metabolize the sugars through glycolysis and convert them into lactic acid. There are two types of lactic acid fermentation:

   • Homolactic fermentation: In this type, the primary product is lactic acid alone.
   • Heterolactic fermentation: Produces lactic acid, ethanol, and CO₂.

4. Process Conditions:

   • pH: The fermentation is generally carried out at a pH of around 5.0–6.0, as this is the optimal range for lactic acid bacteria.
   • Temperature: The temperature is typically maintained between 30-40°C.
   • Time: Fermentation can last between 24 to 48 hours, depending on the strain used and substrate.

5. Recovery: Once fermentation is complete, the lactic acid is recovered. The medium is first filtered to remove microbial biomass, and then lactic acid is purified using techniques like precipitation and crystallization.

Production of Fungal Diastase by Fermentation

1. Microorganisms: Fungal diastase (also called fungal amylase) is an enzyme produced by certain fungi, most commonly strains of Aspergillus niger or Aspergillus oryzae. These fungi are known for their ability to secrete high levels of enzymes.

2. Fermentation Substrates:

   • The production of fungal diastase requires starch-rich materials like grains (e.g., barley, corn), rice bran, or potato starch.
   • These substrates act as the nutrient source for the fungi and also provide the material that the diastase will break down into sugars.

3. Aerobic Fermentation:

   • The fermentation process for fungal diastase is aerobic, meaning it requires oxygen. The fungi grow in a nutrient-rich environment and secrete diastase as a byproduct.
   • Fungal diastase works by hydrolyzing starches into simpler sugars like maltose and glucose.

4. Process Conditions:

   • pH: The pH is kept at around 4.5–6.0 to optimize fungal growth and enzyme production.
   • Temperature: Ideal temperatures for fungal diastase production are between 30-35°C.
   • Time: The fermentation can take 48-72 hours, depending on the fungal strain and substrate used.

5. Recovery: Once the fermentation is complete, the culture is filtered to separate the fungal biomass from the liquid containing the diastase enzyme. The enzyme is then further purified and concentrated through processes like precipitation and lyophilization (freeze-drying).

Applications:

• Lactic acid is widely used in the food industry (as a preservative, acidulant), in pharmaceuticals, and in the production of biodegradable plastics (polylactic acid).
• Fungal diastase is used as a digestive aid, particularly to break down starch in foods, and in brewing, baking, and the production of syrups.