Tuesday, March 1, 2011

Single Cell Protein - Algae

Spirulina
Since a decade ago studies on Single Cell Protein (SCP) had drawn the attention of scientist to bridge the protein gap. The use of algae as food and feed is known since centuries as they form part of the diets is East Asian countries as well as the natives in Central Africa. Some of the algae like Chloralla, Soenedesmus, Coelastrum and Spirulina have been found to suitable for mass cultivation and utilization. The advantages in using algae include simple cultivation, effective utilization of solar energy, faster growth and high protein and nutrient content.


Cultivation of Spirulina
 
In tropical countries Spirulina  cultured under authotrophic, heterotrphic and mixotrophic conditions. 

  • Mass cultivation easier than other algal cultivation because aeration of CO2 is not necessary for this species since it can maximally utilizes the amounts of carbon that are supplied by using bicarbonate of the culture medium.   
  • Continues agitation is not very essential to boost up the yield.
  • Because the studies proofing that continuous mixing with paddle wheels or pumps and sporadic manual stirring with brooms are not providing any considerable differences in yields.
  • The optimum temperature for Spirulina is the temperatures in between 25 and 35°C. 
    • The growth will be retarded when the temperatures below 20°C.
    • Although Spirulina seems to be a more thermophilic alga, it could not withstand longer periods at temperatures above 40°C.
  • Light intensities of 30-40 klux were found to be optimal for Spirulina.
    • To maintain these intensities during summer months, scaffoldings were arranged around the ponds and roofed over sparsely with coconut fronds, which cut down the light by 40-50%, but left enough space for ventilation.
Mass cultivation of CYANOTECH CORP.
 
Protein from Spirulina
  • Culture conditions influence the yield as well as the compositions of Spirulina.
  • Approximately 15% of this amount was derived from non-protein nitrogen.
    • The general composition of Spirulina does not indicate the presence of any harmful compound and shows promising properties as food and feed ingredient.


  • The nutritive quality of a protein is determined by its overall amino acid profile, and the content and availability of essential amino acids.
  • The amino acid composition of Spirulina is given in Table 1 and compared with a few data from the literature and the recommended FAO/WHO pattern.
    • The content of lysine and sulphur-containing amino acids (methionine and cystine) in Spirulina is slightly lower than in the recommended pattern. This deficiency, which is common in all types of single cell protein, can be compensated by blending the algae with other conventional protein sources (legumes).
Amino Acid
FAO/WHO
Becker and Venketaraman
Clement et al.
Wu and Pond
Isoleucine
4.0
6.7
6.0
6.0
Leucine
7.0
9.8
8.0
8.7
Valine
5.0
7.1
6.5
6.3
Phenylalanine
6.0
5.3
5.0
4.9
Tyrosine
6.0
5.3
4.0
4.0
Lysine
5.5
4.8
4.6
4.1
Methionine
3.5
2.5
1.4
2.0
Cystine
3.5
0.9
0.4
-
Tryptophan
1.0
0.3
1.4
1.2
Threonine
4.0
6.2
4.6
4.9
Alanine

9.5
6.8
7.7
Argine

7.3
6.5
7.2
Aspartic Acid

11.8
8.6
9.9
Glutamic acid

10.3
12.6
13.5
Glycine

5.7
4.8
4.7
Histidine

2.2
1.8
1.7
Proline

4.2
3.9
3.9
Serine

5.1
4.2
4.5




Data on Amino Acid Composition of Spirulina Protein in Comparison to Data of the Literature and the Recommended Pattern by FAO/WHO (g/16N)
Protein Based Nutritional Value
Ø  By using Protein Efficiancy Ratio (PER), Biological Value (BV), Digestibility Coefficient (DC) and Net Protein Utilization (NPU) the nutritional quality of sun-dried Spirulina will be established.
Protein Source
Drying Method
Protein Level (%)
PER
DC
BV
NPU
Spirulina platensis
Sun drying
10
2.5
95.3
94.4
89.9
Spiruina sp. (Mexico)
Spray drying
10
2.18
-
-
56.6
Spirulina sp. (Chad)
Spray drying
10
1.86
-
-
52.6
Spirulina sp. (Mexico)
Spray drying
10
2.08
-
-
-
Spirulina sp.
Sun drying
10
1.80
82.7
75.0
62.0
Spirulina maxima
Raw
10
-
76.0
63.0
47.7
Spirulina maxima
Stewed
10
-
74.0
51.0
38.0
Spirulina maxima
Spray drying
10
2.00
84.0
68.0
57.0
Supplementary effect of Protein from Spirulina to Other protein sources


Protein Source
Protein Level %
PER
Spirulina
10.0
1.88
Rice
6.3
2.19
Wheat
10.0
1.13
Baker’s yeast
10.0
1.05
Rice + Spirulina (3:1)
8.0
2.33
Rice + Spirulina (1:1)
9.0
2.39
Wheat + Spirulina (3:1)
10.0
1.41
Wheat + Spirulina (1:1)
10.0
1.83
Yeast + Spirulina (1:1)
10.0
1.50



  • The values in the above table indicate that Spirulina represents a naturally good quality protein concentrate which has promising supplementary values to cereals.
  • Both mixtures of Spirulina with wheat and rice had a protein quality higher than cereals alone.
Conclusion
Monoculture of one algal species using the conventional methods is an expensive project. However, Spirulina cultivation can be projected with small investment since costly agitation, aeration nor sophisticated harvesting and drying technology is not required. The simple cultivation technology as well as the good protein value of Spirulina could promote its cultivation to be done in large scale of production.
Spirulina seems to be the most promising strain for developing countries to be added to the array of armaments to nourish the nation’s economical values. The advantages of these algae are easy cultivation, good yields per unit area, good quality of its protein and absence of any harmful or inconvenient side effects.
Refferences
  1. Becker, E.W & Venkataraman L.V. 1984. Productiona and utilization of the blue-green alga Spirulina in India. Biomas., 105-125. 
  2. Clemet, G., Giddey, C., & Menzi, R. 1967. Amino acid composition and nutritional value of the alga Spirulina maxima. J.Sci.Fd.Agric., 18, 497-501.
  3. Wu, J.F. & Pond, W.G. 1981. Amino acid composition and microbial contamination of Spirulina maxima, a blue-green alga, grown on the effluent of different fermented animal wastes. Bull.Environm.Contam.Toxicol., 27, 151-9.
By
Tevan Ramanathan

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