Assistant Professor- Shubham Shukla
Department of Microbiology
Types of Fermentation Processes
1. Solid Substrate Fermentation (SSF)
- Principle: Microorganisms grow on moist solid materials with little/no free water.
- Substrates: Wheat bran, rice bran, sugarcane bagasse, corn cob, soybean meal, cassava peels, oil cakes.
- Microorganisms:
- Fungi: Aspergillus niger, A. oryzae, Rhizopus spp., Penicillium spp.
- Some bacteria (Bacillus spp.) and yeasts.
- Process Steps:
- Substrate preparation (size reduction, moisture adjustment)
- Sterilization (steam)
- Inoculation (spores/cell suspension)
- Incubation (controlled temp & humidity)
- Product extraction (solvent/aqueous)
- Downstream processing
- Products: Enzymes (amylase, cellulase, protease, lipase), citric acid, lactic acid, antibiotics, biofertilizers, flavor compounds.
- Advantages: Low water use, high product concentration, low energy, cheap agro-wastes, mimics natural habitat.
- Disadvantages: Difficult control, heat removal issues, scale-up problems, limited microbes.
- Industrial Applications: Enzyme industry, food biotechnology, biopesticides, waste valorization.
2. Surface Fermentation
- Principle: Microorganisms grow at the air–liquid interface, forming a surface film/pellicle.
- Microorganisms: Aspergillus niger, Acetobacter spp., Penicillium spp.
- Equipment: Shallow trays, large flat vessels, wooden/stainless-steel trays.
- Products: Citric acid, gluconic acid, vinegar (acetic acid), some antibiotics.
- Advantages: Simple equipment, low energy, easy operation.
- Disadvantages: Low productivity, large space needed, high contamination risk, unsuitable for modern large-scale industry.
- Industrial Significance: Historically important before submerged fermentation; now largely obsolete.
3. Submerged Fermentation (SmF)
- Principle: Microorganisms grow fully submerged in liquid medium with agitation & aeration.
- Microorganisms:
- Bacteria: E. coli, Bacillus spp.
- Yeasts: Saccharomyces cerevisiae
- Fungi: Aspergillus spp., Penicillium chrysogenum
- Fermenters Used: Stirred tank, airlift, bubble column fermenters.
- Products: Antibiotics (penicillin, streptomycin), vaccines, amino acids (glutamic acid), organic acids, alcohols, industrial enzymes.
- Advantages: High productivity, easy scale-up, precise control, lower contamination risk, suitable for continuous operation.
- Disadvantages: High water/energy demand, foaming problems, expensive equipment.
- Industrial Importance: Most widely used in modern biotechnology, especially pharma & enzyme industries.
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