Overview on stress-induced strategies for enhanced microalgae lipid production: Application, mechanisms and challenges

Microalgae have been proposed as a potential renewable energy source for biofuel production. However, owing to the low biomass concentration and lipid productivity, the sustainable and industrialized production of microalgae biofuels is still limited. New lipid improvement strategies have appeared at the technology forefront to overcome the bottlenecks. This review comprehensively illustrates the stress-induced strategies of recent studies and achievements in promoting the lipid accumulation of microalgae. Different stress-induced strategies for improving lipid production such as the use of phytohormone, change of cultivation strategies, combined chemical additives and abiotic stresses (nutrient stress, metal ions and wastewater, etc.) are addressed. After a comprehensive analysis, it is shown that the use of phytohormone combined with abiotic stress under two-stage culture condition is a promising stress-induced strategy to promote the microalgae lipid accumulation. Furthermore, the possible mechanisms of using phytohormone and abiotic stress to enhance the microalgae lipid biosynthesis are discussed. This review is dedicated to further accelerate the sustainable development and practical application of microalgae-based biofuel production.