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  Section: General Biotechnology / Microbial Biotechnology
 
 
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Single Cell Protein (SCP) and Mycoprotein

 
     
 

Production of Bacterial and Actinomycetous Biomass

Bacteria are widely used as a source of single cell protein because of their short life cycle (20-30 minutes) and capacity to utilize a wide range of organic substrates as a source of energy. Actinomycetes also utilize these renewable sources as they have more or less same generation rate as bacteria.

 

Since the establishment of British Petroleum in 1960, a significant progress is made in the production of microbial products by using gaseous and liquid hydrocarbons and chemicals derived from them, for example, methanol, ethanol, etc. The Shell Research Limited, U.K. conducted research on pilot plant scale process for the production of bacterial SCP from methane by using Methylococcus capsulatus or mixed culture of Pseudomonas sp., Hyphomicrobium sp., Acinetobacter sp. and Flavobacterium (Litchfield, 1979). Several processes for the production of bacterial SCP from gaseous hydrocarbons have been developed at Kyowa Hakko Kogyo Company, Limited in Japan. Brevibacterium ketoglutamicum ATCC No. 15587 was able to utilize methane, ethane, propane, n-butane, iso-butane, propylene, butylene or mixture of these hydrocarbons (Tanaka et al. 1972). A pilot scale process for the production of Achromobacter delvacvate from diesel oil is developed at the Chinese Petroleum Corporation, Taiwan.

 

Streptomyces. sp. is capable of growing on methanol. Theromonospora fusca, a thermophilic species, degrades 60-65 per cent paper mill fines resulting in 30 per cent protein product. Nowadays, cellulose degrading thermophilic actinomycetes offer a great opportunity to yield SCP from cellulosic wastes.

 

Method of Production

Roth (1982) has described the following steps for the production of bacterial biomass : (i) supply of a nutrient substrate; (ii) formulation of a suitable medium; (iii) multiplication of microorganisms through fermentation, (iv) separation of cellular substances from the left over medium; and (v) further treatment to kill and dry the bacterial biomass.

 

Imperial Chemical Industry (ICI) is a world's leader in biotechnology, as far as the production of a bacterial biomass, pruteen, from Methylophilus methylotrophus is concerned. Pruteen was produced on methanol but it served as high grade protein for animal feed. It contains 72 per cent protein, 86 per cent total lipid and an amino acid profile high in lysin and methionine. The conversion of methanol to SCP by M. methylotrophus is represented by the following equation :

 

Content

Advantages of producing microbial protein

Microorganisms use as single cell protein (SCP)

Substrates used for the production of SCP

Nutritional values of SCP

Genetic improvements of microbial cells

Production of algal biomass

 

Factors affecting bio­mass production

 

Harvesting the algal biomass

 

Spirulina as SCP, cultivation and uses

Production of bacterial and actinomycetous biomass

 

Method of production

 

Factors affecting biomass production

 

Product recovery

Production of yeast biomass

 

Factors affecting growth of yeast

 

Recovery of yeast biomass

Production of fungal biomass (Other than Mushrooms)

 

Growth conditions

 

Organic wastes as substrates

 

Traditional fungal foods

 

 

Shoyu

 

 

Miso

 

 

Sake

 

 

Tempeh  

Mushroom culture

 

Historical background

 

Present status of mushroom culture in India

 

Nutritional values

 

Cultivation methods

 

 

Obtaining pure culture 

 

 

Preparation of spawns

 

 

Formulation and preparation of composts

 

 

Spawning, spawn running and cropping

 

Control of pathogens and pests

 

Cultivation of paddy straw mushroom

 

Cultivation of white button mushroom

 

Cultivation of Dhingri (Pleurotus sajor-caju)

 

Recipes of mushroom

1.72 CH3OH + 0.23 NH3 +1.51 O2  Arrow1.0 CH1.68 O0.36 N0.22 + 0.72 CO2 + 2.94 H2O.

 

Production of SCP by other bacteria and actinomycetes is shown in Table 18.1.

 

Factors Affecting Biomass Production
Growth of bacteria and actinomycetes are affected by many factors, as a result production of biomass on a given substrate significantly changes. These are : (i) suitable strain of bacterial culture ; (ii) genetic stability of bacterial strain; (iii) absence of bacteriophage; (iv) suitable pH 5-7 of growth medium; (v) temperature (15-35°C according to strain); (vi) oxygen/agitation to create aerobic condition; (vii) organic substrate and nitrogen concentrations. Optimum C:N ratio which favors high protein contents in cells and inhibits accumulation of lipid is 10:1; and (viii) maintenance of sterile conditions throughout the growth.

Product Recovery

Like algal biomass, there are many problems related to the recovery of bacterial cells as they are very small and have cell density in the order of 10-20 g/liter. Centrifugation cost is also high. Processes for cell recovery have been devised in such a way that could cut down the cost. Many pilot plants use flocculants and many have set up decanter type centrifuge. For example, Hoechst (Germany) has developed a device for separation of Methylomonas clara from methanol containing culture medium which is based on electrochemical, coagulation and centrifugation. The cells are washed and spent medium is again treated by conventional treatment process as it contains inorganic salts and small amount of cells. Cell biomass is then spray-dried (Faust et al, 1977).
 
     
 
 
     



     
 
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