With increase in population and potential worldwide plant and animal protein shortage the use of microbial biomass as food is gaining commercial interest globally. Single-cell proteins (SCPs) like algae, fungi, yeast and bacteria can be used as a protein supplements or full replacement of plant and animal proteins in human foods or animal feeds. These SCPs can utilize in-expensive feedstock and by-product wastes, including gaseous substrates, such as carbon dioxide (CO2) or methane (CH4) as sources of carbon and energy for growth to produce protein.SCPs have a high nutritive value due to higher protein, vitamin, essential amino acids and lipid content and can be produced at industrial scale using  biotechnology. This can be an alternative to traditional protein sources such as meat, dairy and soy, which possibly cannot be sustainably produced in the long term to satisfy a growing population. The use of SCPs as a source of food can help to meet the increasing demand for protein, and can do so with minimal environmental impact using renewable energy and sustainable feedstock, reducing the need for land, water, and other finite resources. Initial nutritional trials of SCPs show promising results which can now be scaled up.