Effect of ultrasonication, high pressure homogenization and their combination on efficiency of extraction of bio-molecules from microalgae Parachlorella kessleri

Abstract

The disintegration efficiencies of microalgal Parachlorella kessleri cells by ultrasonication (US) and high pressure homogenization (HPH) treatments were investigated. The applied procedures included individual US, individual HPH, or combined US followed by HPH treatments. The test concentrations of cell suspensions were 1% and 10% dry matter. The microstructures of cell suspensions were analyzed using scanning electron microscopy, light microscopy and light scattering techniques. Extraction was characterized by the ionic, Zi, carbohydrate, Zc, protein, Zp, and pigment (dyes), Zd, extraction indexes. Application of US treatment (1% dry matter, 400 W, 30 min) gave Zi ≈ 0.10, Zc ≈ 0.45, Zp ≈ 0.16, and application of HPH treatment (1% dry matter, 400 bar, 4 passes) gave Zi ≈ 0.10, Zc ≈ 0.20, and Zp ≈ 0.11. In both cases, the efficiency of extraction can be arranged as follows: Zi < Zp < Zc. Application of a preliminary US treatment with 10% dry matter and a final HPH treatment with 1% dry matter allows increasing the extraction efficiency and decreasing the energy consumptions. For example, US (1% dry matter, 400 W, 30 min) + HPH (1% dry matter, 1200 bar, 4 passes) treatment (≈105.6 kJ/g dry matter) gave Zi ≈ 0.49, Zc ≈ 0.69, and Zp ≈ 0.32, whereas US (10% dry matter, 400 W, 30 min) + HPH (1% dry matter, 1200 bar, 4 passes) treatment (≈53.8 kJ/g dry matter) gave Zi ≈ 0.76, Zc ≈ 0.83, Zp ≈ 0.74.