Thermophilic algae: A new prospect towards environmental sustainability

Microorganisms are ubiquitous in their habitat inhabiting almost every corner of the earth. The expanding demand and knowledge for sustainability and biotechnological approach for fulfilling food, health and environmental needs have led to study organisms found in extreme conditions. Thermophilic algae are found in hot springs present at globally distinct places with extreme environmental conditions of temperature (>50 °C), light, pH and nutrient composition. Thermophilic algae like Mastigocladus laminosus, Galdieria sulphuraria, Cyanidium caldarium, species of Synechococcus and Thermosynechococcus has been found to have more thermostable enzymes and high GC (guanine-cytosine) content than mesophilic algal forms. Having potential of high CO2 sequestration, thermophilic algae can be used in nutraceuticals, cosmeceuticals, pharmaceuticals, agricultural and fuel industries along to combat global warming and climate change problems and helps to attain sustainable environment. Some members of thermophilic algae including Synechococcus, Mastigocladus and Thermosynechococcus have shown to contain CRISPR-Cas systems in their genome which can be exploited in various genetic engineering tools. Therefore, the present review article discusses the cultivation and harvesting techniques of thermophilic algae using different culturing media. Further, applications on pilot-scale and/or project-scale in terms of fuel (biodiesel) and non-fuel (pigments, thermostable enzymes, nitrogen fixation, wastewater treatment, removal of dyes and heavy metals from industrial effluents etc) of thermophilic algae along with their CO2 sequestration potential are also highlighted. Nitrogen fixation ability of thermophilic algae makes them promising candidates for biofertilizers and their characteristics providing stability in such harsh conditions are also highlighted. Their recent advances in terms of CRISPR-Cas as a genetic tool, challenges and future prospects are also elaborated while preparing the present review article.