Impact of microalgal cell wall biology on downstream processing and nutrient removal for fuels and value-added products

Recent development in strategies to overcome the environmental adversities are focused mainly on lowering the carbon footprints and to decrease the global temperature rise. Bioprocesses based on microalgae are promising due to a large spectrum of possible products, like platform chemicals, proteins and higher value products that can directly impart a fall in the carbon emission. Another promising approach towards sustainability is the integrated bio refinery cultivation of microalgae for waste water treatment with simultaneous production of fuels (alcohol and biodiesel), high value chemicals (Astaxanthin, Lutein, polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA)etc.), proteins etc, but the technology readiness level are rather low and therefore are not established. However, for sustainable, economical and feasible bioprocess strategies using microalgae intra and extracellular bio-components extraction and cell wall disruption techniques should be optimized whereas challenges like high energy consumption involving these stages in the process makes it futile. The efficiency of cell disruption techniques and product extraction varies within different microalgae and depends mainly on the growth conditions and cell wall composition. The current review describes the cell wall structure and its composition of green freshwater microalgae such as Botryococccus braunii, Scenedesmus obliquus, Desmodesmus sp., Chlamydomonas reinhardtii, Chlorella vulgaris, Haematococcus pluvialis and marine forms like Dunaliella salina and Nannocholoropsis gaditana. Further, it highlights the green cell lysis technologies to disrupt cell walls and the future perspectives and challenges of algae in integrated wastewater treatment, CO2 capture, and energy-efficient algal cell wall disruption for utilizing microalgae for fuel production is discussed.