Solid State Fermentation / Solid Substrate Fermentation

Solid-state fermentation (SSF) or Solid Substrate Fermentation has been defined as the fermentation process occurring in the absence or near-absence of free water.

SSF employs natural raw materials as carbon source such as cassava, barley, wheat bran, rice bran, sugarcane bagasse, cassava bagasse, various oil cakes (e.g. coconut oil cake, palm kernel cake, soybean cake, ground nut oil cake, etc), fruit pulps (e.g. apple pomace), corn cobs, saw dust, seeds (e.g. tamarind, jack fruit), coffee husk and coffee pulp, tea waste, spent brewing grains, etc



Advantages of Solid State Fermentation

•Process is simple
•Cost Effective
•Less Effluent release, reduces pollution
•High Titers, (High Product yields)
•Aeration Process is easy
•Resembles the natural habitat of some fungi and bacteria
•Easier downstream processing 

Factors which Influence Solid State Fermentation

•Selection of Micro-organisms 

This is one of the key factor for improved yields of the product. Bacteria, Yeast and Filamentous Fungi can be used. Filamentous Fungi has shown better results growing in the solid substrate

•Substrate 
Substrate also plays important role in determining the growth of micro-organisms, there by increasing the product yield. Substrate is chosen such a way that it should provide physical support as well as nutrients to the growing culture. 

•Substrate is of two types:
One is Specific substrate, which requires suitable value-addition and/or disposal.
The second is for producing a specific product from a suitable substrate.

•Process Optimization 
Includes the optimization of physico-chemical and Biochemical Parameters such as Size, initial moisture, pH and pre-treatment of the substrate, Relative humidity, temperature of incubation, agitation and aeration, age and size of the inoculum, nutrient Supplementation such as N, P and trace elements, supplementation of additional carbon source and inducers, Extraction of product and its purification

Problems Associated with Solid State Fermentation

•Heat Transfer: One of the main difficulty is to control the temperature during the fermentation process.
•Heat is generated during the metabolic activities of micro-organisms, since the substrate used has low thermal conductivity heat removal will be slow.
•When the heat generated goes beyond certain level, which will result in product denaturation and will affect growth of microbe, ultimately ending up in reduction in yield and quality of the product.

Applications of Solid State Fermentation

• Agro-Food Industry

Traditional Food Fermentations :Koji, Fermented Cheeses

Mushroom Production & spawn Production: Agaricus, Pleurotus

Bioconversion By-products: Sugar pulp Bagasse Composting, Detoxication

 Food Additives: Flavours. Dyestuffs. 

• Agriculture Industry

 Biocontrol , Bioinsecticide : Beauveria Metarhizium, Tricho derma

PlantGrowth Hormones / Enhancers : Giberellins, Rhizobium, Trichoderma

• Industrial Fermentation

Enzymes production : Amylases, Cellulases Proteases, Pectinases, Xylanases

Antibiotic production : Pencillin, Feed & Probiotics

Organic acid Production : Citric acid, Fumaric acid,etc

 Fungal Metabolites: Alkaloids

 Ethanol Production: Malting and Brewing

References

•General and microbiological aspects of solid substrate fermentation
•Basics of SSF
•Pandey, Ashok (2008, June 13). Solid-state fermentation. SciTopics