Process Engineering for High-Cell-Density Cultivation of Lipid Rich Microalgal Biomass of Chlorella sp. FC2 IITG
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Process Engineering for High-Cell-Density Cultivation of Lipid Rich Microalgal Biomass of Chlorella sp. FC2 IITG Muthusivaramapandian Muthuraj & Niharika Chandra & Basavaraj Palabhanvi & Vikram Kumar & Debasish Das
# Springer Science+Business Media New York 2014
Abstract In the present study, process engineering strategy was applied to achieve lipid-rich biomass with high density of Chlorella sp. FC2 IITG under photoautotrophic condition. The strategy involved medium optimization, intermittent feeding of limiting nutrients, dynamic change in light intensity, and decoupling growth and lipid induction phases. Medium optimization was performed using combinations of artificial neural network or response surface methodology with genetic algorithm (ANN-GA and RSM-GA). Further, a fed-batch operation was employed to achieve high cell density with intermittent feeding of nitrate and phosphate along with stepwise increase in light intensity. Finally, mutually exclusive biomass and lipid production phases were decoupled into twostage cultivation process: biomass generation in first stage under nutrient sufficient condition followed by lipid enrichment through nitrogen starvation. The key findings were as follows: (i) ANN-GA resulted in an increase in biomass titer of 157 % (0.95 g L−1) in shake flask and 42.8 % (1.0 g L−1) in bioreactor against unoptimized medium at light intensity of 20 μE m−2 s−1; (ii) further optimization of light intensity in bioreactor gave significantly improved biomass titer of 5.6 g L−1 at light intensity of 250 μE m−2 s−1; (iii) high cell density of 13.5 g L −1 with biomass productivity of Electronic supplementary material The online version of this article (doi:10.1007/s12155-014-9552-3) contains supplementary material, which is available to authorized users. M. Muthuraj : N. Chandra : B. Palabhanvi : D. Das (*) Department of Biotechnology, Indian Institute of Technology, Guwahati, Assam 781039, India e-mail: [email protected] D. Das e-mail: [email protected] V. Kumar : D. Das Centre for Energy, Indian Institute of Technology, Guwahati, Assam 781039, India
675 mg L−1 day−1 was achieved with dynamic increase in light intensity and intermittent feeding of limiting nutrients; (iv) finally, two-phase cultivation resulted in biomass titer of 17.7 g L−1 and total lipid productivity of 313 mg L−1 day−1 which was highest among Chlorella sp. under photoautotrophic condition. Keywords Microalgae . Optimization . Artificial neural network . Genetic algorithm . Light intensity . Fed-batch
Introduction Photosynthetic microbes like microalgae have gained major attraction as a renewable feedstock for biofuel generation and as a cellular factory for synthesis of various therapeutic molecules and fine chemicals [1]. These organisms are also believed to be the potential alternative, renewable, and sustainable source of biodiesel attributed to their higher lipid content, photosynthetic efficiency, and CO2 sequestration ability in comparison to other photosynthetic systems like plants [2]. Neutral lipids
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