Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Sat, 10 Nov 2018 15:51:53 Lipid production and mixotrophic growth features of cyanobacterial strains isolated from various aquatic sites Sima Modiri, 1 Hakimeh Sharafi, 1,2 Leila Alidoust, 1 Hamidreza Hajfarajollah, 1 Omid Haghighi, 1 Aisan Azarivand, 1 Zahra Zamanzadeh, 1 Hossein Shahbani Zahiri, 1 Hojatollah Vali 3 and Kambiz Akbari Noghabi 1 Correspondence Kambiz Akbari Noghabi Akbari@nigeb.ac.ir Received 19 December 2014 Accepted 6 January 2015 1 Division of Industrial & Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), PO Box 14155-6343, Tehran, Iran 2 Department of Microbiology, Faculty of Sciences, Alzahra University, Tehran, Iran 3 Facility for Electron Microscopy Research, McGill University, 3640 Street, Montreal, Quebec, Canada The present study was conducted to determine the potential of five cyanobacteria strains isolated from aquatic zones to induce lipid production. The phylogenetic affiliation of the isolates was determined by 16S rRNA gene sequencing. Amongst the isolates, an efficient cyanobacterium, Synechococcus sp. HS01 showing maximal biomass and lipid productivity, was selected for further studies. In order to compare lipid productivity, the HS01 strain was grown in different media to screen potential significant culture ingredients and to evaluate mixotrophic cultivation. Mixotrophic cultivation of the strain using ostrich oil as a carbon source resulted in the best lipid productivity. GC analysis of fatty acid methyl esters of the selected cyanobacterial strain grown in media supplemented with ostrich oil showed a high content of C16 (palmitoleic acid and palmitic acid) and C18 (linoleic acid, oleic acid and linolenic acid) fatty acids of 42.7 and 42.8 %, respectively. Transmission electron micrographs showed that the HS01 cells exhibited an elongated rod-shaped appearance, either isolated, paired, linearly connected or in small clusters. According to initial experiments, ostrich oil, NaNO 3 and NaCl were recognized as potential essential nutrients and selected for optimization of media with the goal of maximizing lipid productivity. A culture optimization technique using the response surface method demonstrated a maximum lipid productivity of 56.5 mg l ”1 day ”1 . This value was 2.82-fold higher than that for the control, and was achieved in medium containing 1.12 g l ”1 NaNO 3 , 1 % (v/v) ostrich oil and 0.09 % (w/v) NaCl. INTRODUCTION Over the last few years, increasing petroleum costs and, more importantly, environmental concerns have driven scientists to develop new technical knowledge and skills about renewable energy sources. Biodiesel is currently receiving considerable attention due to its great potential as a sustainable and environmentally friendly alternative to petroleum-based fossil fuels (Griffiths & Harrison, 2009). Global concern about exhausting petroleum reservoirs is one reason for the increasing level of research on biodiesel production (Schenk et al., 2008). Therefore, searching for renewable energy sources is necessary and finding new clean energy resources has become one of the most daunting challenges of the world. Cyanobacterial lipid could be one of the promising feed- stocks for biodiesel production (Rittmann, 2008; Yang et al., 2011). As common photosynthetic prokaryotic organisms, cyanobacteria can be technologically developed as an excellent microbial cell factory that can harvest solar energy and transform atmospheric carbon dioxide to useful organic compounds (de Loura et al., 1987; Parmar et al., 2011). Lipids, carotenoids, pigments, vitamins and aromatic compounds are amongst the bioproducts of cyanobacteria. Abbreviations: DCW, dry cell weight; FAME, fatty acid methyl ester; FTIR, Fourier transform IR spectroscopy; RSM, response surface method; SEM, scanning electron microscopy; TEM, transmission electron microscopy. One supplementary table and five supplementary figures are available with the online Supplementary Material. Microbiology (2015), 161, 662–673 DOI 10.1099/mic.0.000025 662 000025 G 2015 The Authors Printed in Great Britain