Effects of fluctuating temperature and silicate supply on the growth, biochemical composition and lipid accumulation of Nitzschia sp. Yuelu Jiang a,⇑ , Katherine Starks Laverty a , Jola Brown b , Marcella Nunez a , Lou Brown b , Jennifer Chagoya c , Mark Burow c , Antonietta Quigg a,d a Department of Marine Biology, Texas A&M University at Galveston, Galveston, 77553 TX, USA b Texas Agrilife Research, Texas A&M University, Pecos, 79772 TX, USA c Texas AgriLife Research, Texas A&M System, Lubbock, 79403 TX, USA d Department of Oceanography, Texas A&M University, College Station, 77843 TX, USA highlights  Low Si limited growth in both growth and lipid formation media under 3 seasons.  Winter condition introduced higher percentage of unsaturated fatty acids.  Saturated fatty acids and monounsaturated fatty acids were most abundant in summer.  In winter, poly-unsaturated fatty acids increased with the increase of Si. article info Article history: Received 14 October 2013 Received in revised form 11 December 2013 Accepted 14 December 2013 Available online 22 December 2013 Keywords: Seasonal variation Nitzschia sp. Growth Lipid Silicate limitation abstract Nitzschia sp. (Bacillariophyceae) was grown under temperature and photoperiods mimicking those, typical during summer, spring/fall and winter conditions in the southern United States, and using five sil- icate (Si) concentrations. In general, higher Si concentrations resulted in higher growth rates in summer and spring/fall conditions and lower organic content. Si-deficient Nitzschia sp. had higher levels of neutral lipid compared to those growing in Si replete media. Under summer conditions, the proportion of satu- rated fatty acids (SFA) and monounsaturated fatty acids (MUFA) was relatively stable compared with spring/fall and winter conditions, and the proportion of polyunsaturated fatty acids (PUFA) was low. In the winter condition, SFA and MUFA showed a gradient of decreasing abundance while PUFA gradients increased with increasing Si concentrations in the medium. Cumulative productivity (optimization of growth and lipid content) would be best in the spring/fall but less so in the other conditions for this strain of Nitzschia sp. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Microalgae efficiently convert CO 2 to potential biofuels, feeds and high-value byproducts using a small foot print (Chisti, 2007). Microalgae can grow on non-arable land and use non-potable water without displacing food crops. This growth is considered environmental friendly as microalgal biofuels can take advantage of nutrients in wastewater and CO 2 from power plants; while crop plants cannot use these resources (Chisti, 2007). Other factors, which should be considered simultaneously for sustainable biofuel production include but are not limited to: lipid and high added-va- lue chemicals production (e.g. for pharmaceutical or cosmetic industry), extraction economics (solvents, ultrasound application, electromagnetic field use, etc.), incineration/pyrolysis/gasification of residual biomass, its anaerobic digestion for biogas production, etc. These factors have been reviewed recently in Chisti (2007), Schenk et al. (2008) and Šoštaric ˇ et al. (2012). Issues in large scale biofuels production with microalgae in open ponds are contamination, lack of control over temperature and light, loss of water by evaporation, grazing by protozoa and zooplankton, fungal parasites and viral infections. Pulz and Gross (2004) reported that successful algal biotechnology mainly depends on choosing the right alga with relevant properties for specific culture conditions and products. Large-scale production 0960-8524/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2013.12.068 Abbreviations: AFDW, ash-free dry weight; C, carbon; DW, dry weight; FAMEs, fatty acid methyl esters; GC, gas chromatography; MS, mass spectrometer; MUFA, mono-unsaturated fatty acids; NR, Nile Red; N, nitrogen; OD, optical density; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; Si, silicate. ⇑ Corresponding author. Present address: Institute of Ocean Science and Tech- nology, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China. Tel.: +86 755 2603 6257; fax: +86 755 2603 6322. E-mail address: jiang.yuelu@sz.tsinghua.edu.cn (Y. Jiang). Bioresource Technology 154 (2014) 336–344 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech