Deferentiate between surface and submerged fermentation?

Surface fermentation and submerged fermentation are two distinct methods used in industrial biotechnology for the production of various compounds such as antibiotics, organic acids, enzymes, and beverages. Let's differentiate between the two:

Surface Fermentation:

1. Characteristics: Surface fermentation occurs on the surface of a liquid medium in fermentation vessels or trays. Microorganisms grow as a film or pellicle on the liquid's surface, where they have direct access to oxygen from the air.

2. Oxygen Requirement: Surface fermentation is best suited for microorganisms that require oxygen for their growth and metabolic activities. These microorganisms form visible colonies or mycelial mats on the liquid's surface.

3. Agitation and Aeration: Surface fermentation typically involves minimal agitation or aeration of the culture medium. Oxygen is passively supplied by diffusion from the air, and mixing is limited to prevent damage to the surface-growing microorganisms.

4. Examples: Some common examples of surface fermentation include:

- Production of antibiotics such as penicillin and streptomycin using fungi.

- Brewing of traditional beers with top-fermenting yeasts that form a layer on the surface during fermentation.

- Production of tempe, a fermented soybean product popular in Indonesia, using the fungus Rhizopus oligosporus.

Submerged Fermentation:

1. Characteristics: Submerged fermentation occurs when microorganisms are completely immersed and dispersed throughout a liquid medium in fermentation vessels or bioreactors. Oxygen is typically provided by aeration or sparging.

2. Oxygen Requirement: Submerged fermentation is suitable for both aerobic and anaerobic microorganisms. Aerobic organisms require oxygen throughout the process, while anaerobic organisms can thrive in the absence of oxygen.

3. Agitation and Aeration: Agitation and aeration are crucial in submerged fermentation to provide oxygen to microorganisms and ensure uniform mixing of nutrients and waste removal. Agitation can be achieved through mechanical means (impellers, paddles) or by injecting air or other gases into the culture medium.

4. Examples: Some common examples of submerged fermentation include:

- Production of citric acid using the fungus Aspergillus niger.

- Fermentation of submerged lactic acid bacteria (LAB) for the production of yogurt and other fermented dairy products.

- Fermentation of submerged yeast strains for the production of biofuels, such as ethanol.

In summary, surface fermentation occurs on the surface of a liquid medium with limited agitation, suitable for oxygen-requiring microorganisms. Submerged fermentation takes place within a liquid medium with more extensive agitation and aeration, catering to both aerobic and anaerobic microorganisms. The choice of fermentation method depends on the specific requirements and characteristics of the desired product and the microorganisms involved.