Process Optimization of Microwave-Assisted Extraction of Chlorophyll, Carotenoid and Phenolic Compounds from _Chlorella vulgaris_ and Comparison with Conventional and Supercritical Fluid Extraction  
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pigments is also considered remarkable [8]. The aforementioned biocomponents are well-known for demonstrating curative and repairing effects and exhibiting antibacterial, antifungal, and antioxidant activity [9].  
In recent years, microwave-assisted extraction (MAE) has been applied to extract biocomponents from microalgae biomass [10]. MAE is considered a non-conventional method [11], during which microwave radiation is rapidly absorbed by the biomass and converted into thermal energy. The biomass is heated through dipole rotation and ionic conduction [12]. The microwave energy absorption and, thus, heat generation can be measured through the dissipation factor (tan \(\delta\)). This term is proportional to the dielectric loss (\(\varepsilon^{\prime\prime}\)) and inversely proportional to the dielectric constant (\(\varepsilon^{\prime}\)) of the solvent, indicating that the presence of polar solvents is considered necessary [13]. In contrast to the conventional solid-liquid extraction, the non-conventional method of MAE offers reduced thermal gradients and instant heating of the biomass, as well as enhanced extraction yield during rapid extractions and decreased solvent quantities [14; 15]. In the case of _Chlorella_, the studies of MAE are mainly focused on lipid extraction [16; 17; 18; 19] followed by carotenoids [20; 21], whereas few studies have dealt with the extraction of bioactive compounds such as proteins [22] and polysaccharides [23].  
The studies of MAE concerning _Chlorella_ biomass have been limited to the investigation of individual component categories. Nevertheless, studying a multitude of bioactive compounds derived from _Chlorella_'s extracts, along with their antioxidant activity, would be considered useful for the utilization of such products in demanding industrial fields.  
The aim of the present work is the study of the non-conventional microwave-assisted extraction (MAE) of high value-added biocomponents from _Chlorella vulgaris_ biomass, utilizing the green solvent aq. ethanol 90% \(v/v\). MAE's study included the investigation of essential process parameters, quantitative and qualitative effect study, data correlation and process optimization. The variations of extraction temperature (40-60 \({}^{\circ}\)C), duration (5-25 min), solvent-to-biomass ratio (20-90 mL\({}_{\text{solv}}/\text{g}_{\text{biom}}\)), and microwave power (300-800 watts) were investigated regarding the effect on the extraction yield, extract's total phenolic and pigment (chlorophylls and carotenoids) content, and antioxidant activity. The advantageous acquaintance of this work is not only the effect study of MAE's operational conditions on extract's several bioactive compounds and antioxidant activity but also the beneficial comparison of MAE with different extraction methods. More specifically, the results of optimized MAE were compared with the conventional solid-liquid extraction (SLE) and the novel supercritical fluid extraction (SFE).