Microalgae contain both chlorophyll a and chlorophyll b. Intracellular chlorophyll a content can vary from 0.0041 g/g dried microalgae (Synechococcus sp.) to 0.0185 g/g dried microalgae (Nannochloropsis gaditana) [53]. In green microalgae, the ratio of chlorophyll a/chlorophyll b ranges broadly from 0.64 to 5, in contrast to higher plants which have a narrower range from 1 to 1.4. The chlorophyll content and profile of a microalgal species continuously change depending on its life cycle and cultivation conditions (medium composition, nutrient availability, temperature, illumination intensity, ratio of light and dark cycle, aeration rate). Certain green microalgae, such as Chlamydomonas, Chlorella, and Scenedesmus sp., have mutants that can synthesize chlorophyll in the dark during heterotrophic growth [53] .

Figure 2 shows the downstream processing steps required to produce chlorophyll from microalgae, while Table 1 provides a list of different technologies currently

available for each step. After the microalgal culture is harvested from its cultivation system, it is concentrated in the dewatering step to yield a wet paste. Afterwards, the microalgal pellet undergoes a pre-treatment step for preparation towards chloro­phyll extraction. The chlorophylls are then extracted from cellular materials before being purified in a fractionation step [24].