A number of studies have recently been focusing on the potential of microalgae for bioremediation of wastewater and as feedstock for biofuel production. Compared to crop plants, microalgae farming requires lesser resources, non-arable land and does not compete economically with the food industry. Lipid yield from microalgae is reported to be higher than current biofuel producing crops. However, biofuel production from algae is yet not sustainable or economical enough to compete with fossil fuels. This thesis highlights the importance of oxidative stress pathway in microalgae and how better knowledge of this area may help to engineer robust and sustainable strains of microalgae, capable of thriving in toxic wastewater conditions. Focus of the thesis is largely towards the expression of anti-oxidative stress pathway genes in microalgae, under influence of various oxidative stress- inducers.