Fermentation Fermentation Submerged fermentation Smf Liquid fermentation Lf

Fermentation

Fermentation • Submerged fermentation (Smf)/ Liquid fermentation (Lf) • Solid state fermentation (SSF)

Submerged fermentation • Media concentration is very much lower as compared to water content. • Required processed ingredients are expensive • Higher water activity becomes the major cause of contamination in SLF • Large-scale bioreactors are required because media is very much diluted.

• High air pressure consumes more power and there is poor transfer of gas in SLF • Vigorous mixing makes diffusion easy. • Online sensors are available and sampling is easy for biomass measurement. • Water makes downstream process difficult and very expensive. • High quantity of liquid waste is produced, causes difficulties in dumping

Solid state fermentation (SSF) • Organisms requiring less water for growth are preferred such as filamentous fungi. • Inert support (natural or artificial), containing all components for growth in the form of solution • Less chances of contamination because of low availability of water • Small size bioreactors can be used.

• Less consumption of energy for aeration and gas transfer. • Limiting factor for growth is diffusion of nutrients • Lots of difficulties in measuring the quantity of biomass present and other online processes • Downstream processing is easy, cheaper and less time consuming. • Liquid waste is not produced

Solid substrate Fermentation 1 Pretreatment of a substrate that often requires mechanical, chemical or biological processing; 2 Hydrolysis of primarily polymeric substrates, e. g. polysaccharides and proteins; 3 Utilization of hydrolysis products 4 Separation and purification of end-products. • Monoculture • Dual culture • Mixed culture

Environmental parameters that influence solid-substrate fermentations • Water activity • Temperature • Aeration

Bioreactors used for solidsubstrate fermentations 1 Rotating drum fermenters 2 Tray fermenters 3 Bed systems 4 Column bioreactors 5 Fluidized bed reactors-

1. Rotating drum fermenters • 100 L capacity • Enzymes , microbial biomass production • Filled to 30% capacity, inefficient mixing

2. Tray fermenters • • Used for enzymes, fermented foods Few cm depth, stacked Large volume incubation chambers 150 m 3 capacity

3. Bed systems • Commercial koji production • Bed of substrate up to 1 m deep • Humidified air is forced

4. Column bioreactors • Column type – glass , plastic • Loosely packed • Organic acids, ethanol Biomass

5. Fluidized bed reactors • Continuous agitation with forced air • Air prevent adhesion or aggregation of substrate particles • Biomass production for animal feed