[SagarikaGhosh]

Since ancient times, people near Lake Chad Africa and the Aztecs near Lake Texcoco, Mexico harvested the filamentous blue green alga, Spirulina, from the lake, dried in the sun and used as food. Such kinds of food are known as single cell proteins. Other than Spirulina, microbes like baker’s yeast, Brevibacterium sp, Candida utilis, and K. fragilis are also being used as SCP.

Given below is the basic production process for a SCP:

1. Provide a carbon source e.g. carbon dioxide in case of Spirulina. Some carbon sources may require physical or chemical pretreatments.

2. To the carbon source add nitrogen, phosphorous and other nutrient sources needed for optimal growth of the microorganisms.

3. Maintain sterile or hygienic conditions to prevent contamination.
Autoclave the equipments used and filter the medium.

4. Inoculate the selected microorganism in a pure state.

5. Provide adequate aeration in case of aerobic processes (not required in case of algae). Also ensure that the optimum temperature is maintained and heat generated is quickly dissipated.

6. Recover the microbial biomass from the medium. This depends on the type of microorganism being used but in case of filamentous organisms like algae and fungi, filtration is done followed by pressing. Sun drying is a slow but cheap process for biomass recovery. However, it reduces the quality of the SCP.

7. Process the biomass for enhancing the quality and stability. This may include techniques for reducing the nucleic acid content, protein isolation and purification.

After the microbial mass has been harvested and recovered, it has to be evaluated for its nutritional quality. Some of the characteristics that need to be considered are protein, amino acid, nucleic acid, lipid, vitamin etc contents. Also the SCP has to be analyzed for presence of any heavy metals or toxins, polycyclic hydrocarbons etc. In order to pass the evaluation the SCP produced has to have specific density, particle size, texture color- all of which are standardized and regulated by the health regulatory bodies. It is mandatory that the microbiological description be provided. This may include species, strain, information on contamination etc. The most important quality however that needs to be evaluated and mentioned clear on the packaging is the nutritional value with regard to the target species. Apart from all these evaluations, any product has to undergo a variety of tests before being made available commercially for human consumption.