Cultivation of <i>Spirulina </i>in Gas Induced Photobioreactor and Isolation of Phycobiliproteins

Abstract

A novel design of Gas Induced Mechanically Agitated Photobioreactor (GIMAP) using the principle of hollow shaft impeller to sparge air is tested with <i>Spirulina </i>as model system. Gas induced impeller is a lesser-explored type of mechanically agitated contactor. It possesses unique characteristics like no separate power requirement for the sparging of the gas, moderate values of mass transfer coefficient and relatively low values of shear stress. These

characteristics make it suitable as a photobioreactor although it may not be the best choice for the classical fermentations. GIMAP exhibited good performance giving biomass concentration and high specific growth rate of 4.44 g/l and 1.33 d^-1, respectively. Hydrodynamic stress developed in GIMAP was found to have favourable effect

that resulted in production of biomass with more permeable cell walls. As a result it was possible to extract phycobiliproteins without cell rupture by simply changing the <i>p</i>H<i> </i>of the buffer. Further it was possible to recover 23% of phycobiliproteins (92% yield) from the GIMAP culture along with a by-product namely exhaust cell mass with 25% proteins. Simpler downstream processing, additional byproduct coupled and higher growth rates of

<i>Spirulina </i>than the conventional cultivation methods indicate the commercial potential of the proposed GIMAP design as photobioreactor.