# Extraction of Pigments from Microalgae and Cyanobacteria--A Review on Current Methodologies
## 9 Novel Extraction Methodologies  
Novel methodologies have been suggested for cell disruption and extraction of valuable compounds from microalgae and cyanobacteria in special pigments. These methodologies are usually adaptations of the already-mentioned technologies or have the same  
Figure 7: Schematic representation of cell milking in microalgae and cyanobacteria cells. fundamental principles as a basis. The next few paragraphs will detail the applicability of laser, hydrodynamic cavitation, flotation, high-voltage electrostatic fields, and ohmic heating for the extraction of microalgae and cyanobacteria products. Laser is a wave-based mechanical method for cell disruption, as with ultrasounds and microwaves. [PERSON] et al. [75] showed the use of laser as alternative for cell disruption in _Nannochloropsis oculata_. The laser (1064 nm) used a third of the energy of microwave extraction in order to obtain the same yield of disruption (95%). The biggest issue with using laser for large-scale production is the difficulty of scaling-up. In that study, the laser extraction was performed in only 30 \(\upmu\)L of matrix. Regarding hydrodynamic cavitation, cell disruption occurs after the formation of microbubbles in the medium, which produce shock waves upon collapsing, momentarily inducing higher pressure and temperature. These environmental changes created by those shock waves are responsible for cell breakage. [PERSON] and [PERSON] [76] applied hydrodynamic cavitation to _N. salina_ for cell wall disruption and lipid extraction, and this method seems to be as suitable as ultrasonication. On the other hand, hydrodynamic cavitation requires an efficient cooling system, proper facility design, and maintenance of high fluid velocity for the cavitation effect, leading to significant increases in the cost of the process [30]. Also based on bubble formation, the liquid biphasic flotation combines solvent sublimation and a liquid biphasic system. The extraction occurs by selective adsorption of target compounds on air bubbles connecting a two-phase system: one salt-rich aqueous phase and the other an organic phase. Liquid biphasic flotation has been suggested for the extraction of astaxanthin from _H. pluvialis_ by using 2-propanol as the organic phase and (NH4)2 SO4 as salt for the aqueous phase [77]. The system can be scaled-up, although it requires a large amount of salt and organic solvents. Moreover, the use of novel methodologies of electric field extraction--high voltage electrical discharge and ohmic heating--seems to present the most scalable and economically viable options. High voltage electrical discharge (HVED) uses continuous electric field of high intensity (\(E>10\) kV.cm\({}^{-1}\)) for extraction, which can also preserve the compounds' stability and the overall quality of the final product. However, only a few studies have used this methodology for extraction [78]. In addition, the requirement for high amounts of energy makes this method less attractive than other electric-based systems. [PERSON] et al. [79] used HVED for extraction in _N. oculata_, and suggested a two-phase extraction for chlorophyll, carotenoids, and lipids using HVED as a pre-treatment with aqueous washing, followed by vacuum drying and an organic solvent extraction. In the case of ohmic heating (OH), an electric field of low to moderate intensity is applied with an alternate current, causing internal heat generation (the Joule effect) that can enhance cell breakage or electroporation [80]. This methodology does not have restrictions in processing times and is currently used in foods thermal processing, mainly due to the uniformity of heating, controllable heating rate, cost, and energy efficiency [47]. Although the use of ohmic heating has been suggested for the extraction of pigments in plants [81; 82], only a few studies have suggested the use of this methodology in algae matrices. [PERSON] et al. [83] suggested the use of OH as a pre-treatment of _Chorella_ sp. biomass for the production of biodiesel.