Improvement of Medium Composition and Utilization of Mixotrophic Cultivation for Green and Blue Green Microalgae towards Biodiesel Production

Abstract

A possible source of biological material for the production of biodiesel is represented by microalgae, in particular by their lipid content. The aim of the present work was to optimize culture medium composition for improving growth and lipid content of green microalgae Chlorella sorokiniana , Scenedesmus acuminatus and blue green Cyanobacterium aponicum . Lipids were quantitatively determined by spectrofluorometric method using Nile red flurometric stain. Initially, the effect of two different medium types, Bold ’ s and optimized culture medium (OCM), four types of carbon source (glucose and sodium acetate, molasses, glycerol, control) and four nitrogen concentrations (100%, -75%, -50%, -25%) on the enhancement of biomass and lipid content and lipid productivity were studied; indeed, optimized culture medium significantly improved growth, CDW for three microalgae, beside increasing lipid content and lipid productivity for S. acuminatus and C. aponicum by 7.5 and 5 folds respectively at 25 th day compared to Bold ’ s medium. Moreover, 25% nitrogen deficient medium significantly increased lipid content and lipid productivity for both C. sorokiniana and C. aponicum at 2 nd week of re-propagation to 10.6 and 2.6 folds over control (100% nitrogen). While S. acuminatus recorded the significant lipid content & productivity at 2 nd week under recommended nitrogen dose in medium (100% N) by 4.4 folds over 25% deficient medium. Meanwhile 0.3% glycerol medium enhanced CDW, lipid content of S. acuminatus to 1.68 gL - 1 . While C. sorokiniana and C. aponicum recorded significant CDW under 0.3% acetate medium 1.37 and 0.76 gL - 1 . C. aponicum exhibited no growth under glycerol medium. The highest lipid content and lipid productivity were obtained under glycerol medium for C. sorokiniana and S. acuminatus (64.3 and 52.8 mg·g ·g &#45 1 ·d &#45 1 ).