Chlorophyll is a commercially important natural green pigment responsible for the absorption of light energy and its conversion into chemical energy via photosynthesis in plants and algae. This bioactive compound is widely used in the food, cosmetic, and pharmaceutical industries. Chlorophyll has been consumed for health benefits as a nutraceutical agent with antioxidant, anti-inflammatory, antimutagenic, and antimicrobial properties. Microalgae are photosynthesizing microorganisms which can be extracted for several high-value bioproducts in the biotechnology industry. These microorganisms are highly efficient at adapting to physicochemical variations in the local environment. This allows optimization of culture conditions for inducing microalgal growth and biomass production as well as for changing their biochemical composition. The modulation of microalgal culture under controlled conditions has been proposed to maximize chlorophyll accumulation. Strategies reported in the literature to promote the chlorophyll content in microalgae include variation in light intensity, culture agitation, and changes in temperature and nutrient availability. These factors affect chlorophyll concentration in a species-specific manner; therefore, optimization of culture conditions has become an essential requirement. This paper provides an overview of the current knowledge on the effects of key environmental factors on microalgal chlorophyll accumulation, focusing on small-scale laboratory experiments.

The findings acquired in this work are of great biotechnological importance to extend knowledge of choosing the right culture condition to stimulate the effectiveness of microalgae strains for chlorophyll production purposes.

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SUMMARY Biodiesel is a renewable fuel produced mostly from edible and non‐edible vegetables, by transesterification of neutral lipids (triacylglycerols). However, vegetable oil‐based biodiesel production competes with food crops for arable land, increasing food prices and leading to biodiversity loss. The production of biodiesel from oleaginous microorganisms – particularly microalgae – has attracted attention due to the higher lipid productivity of these organisms, when compared with vegetables. Several environmental factors – including light, temperature, pH and the presence of nutrients (particularly nitrogen, phosphorus and iron) – influence directly the ability of microalgae to produce and store triacylglycerols and other lipids, and also modulate microalgal growth. Although some environmental factors affect several species in a similar manner, differential responses between species are frequent, highlighting the importance of identifying optimal cultivation conditions for each species, to balance growth and lipid productivity for biodiesel production. Here, we reviewed the particular influence of the physicochemical and nutritional factors on the growth and lipid productivity of different green oleaginous microalgae species.