Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech Exploring the potency of integrating semi-batch operation into lipid yield performance of Chlamydomonas sp. Tai-03 Chung Hong Tan a , Pau-Loke Show a, ⁎ , Tau Chuan Ling b , Dillirani Nagarajan c,d , Duu-Jong Lee d , Wei-Hsin Chen e,f , Jo-Shu Chang c,f,g,h a Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham Malaysia Campus, Jalan Broga, Semenyih 43500, Selangor Darul Ehsan, Malaysia b Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia c Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan d Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan e Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, Taiwan f Research Center for Circular Economy, National Cheng Kung University, Tainan 701, Taiwan g Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan h College of Engineering, Tunghai University, Taichung 407, Taiwan GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Biodiesel Microalgae Organic carbon Medium replacement Semi-batch ABSTRACT Third generation biofuels, also known as microalgal biofuels, are promising alternatives to fossil fuels. One attractive option is microalgal biodiesel as a replacement for diesel fuel. Chlamydomonas sp. Tai-03 was pre- viously optimized for maximal lipid production for biodiesel generation, achieving biomass growth and pro- ductivity of 3.48 ± 0.04 g/L and 0.43 ± 0.01 g/L/d, with lipid content and productivity of 28.6 ± 1.41% and 124.1 ± 7.57 mg/L/d. In this study, further optimization using 5% CO 2 concentration and semi-batch operation with 25% medium replacement ratio, enhanced the biomass growth and productivity to 4.15 ± 0.12 g/L and 1.23 ± 0.02 g/L/d, with lipid content and productivity of 19.4 ± 2.0% and 239.6 ± 24.8 mg/L/d. The major fatty acid methyl esters (FAMEs) were palmitic acid (C16:0), oleic acid (C18:1), and linoleic acid (C18:2). These short-chain FAMEs combined with high growth make Chlamydomonas sp. Tai-03 a suitable candidate for bio- diesel synthesis. https://doi.org/10.1016/j.biortech.2019.121331 Received 7 February 2019; Received in revised form 7 April 2019; Accepted 8 April 2019 ⁎ Corresponding author at: The University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia. E-mail address: PauLoke.Show@nottingham.edu.my (P.-L. Show). Bioresource Technology 285 (2019) 121331 Available online 11 April 2019 0960-8524/ © 2019 Elsevier Ltd. All rights reserved. T