Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej A novel investigation of the growth and lipid production of the extremophile microalga Coccomyxa melkonianii SCCA 048 under the efect of diferent cultivation conditions: Experiments and modeling Santina Soru a , Veronica Malavasi a , Alessandro Concas b, ⁎ , Pierluigi Caboni c , Giacomo Cao a,d, ⁎ a Interdepartmental Center of Environmental Science and Engineering (CINSA), University of Cagliari, Via San Giorgio 12, 09124 Cagliari, Italy b Center for Advanced Studies, Research and Development in Sardinia (CRS4), Loc. Piscina Manna, Building 1, 09010 Pula, CA, Italy c Department of Life and Environmental Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy d Department of Mechanical, Chemical and Materials Engineering, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy HIGHLIGHTS • The extremophile strain Coccomyxa melkonianii SCCA048 was investigated. • The pH and nitrate dependent kinetics were investigated for the frst time. • The strain demonstrated to be able of growing under a wide range of pH conditions. • Good lipid productivity and FAMEs composition were achieved under specifc conditions. • Experimental results were successfully interpreted by a novel mathematical model. ARTICLE INFO Keywords: Extremophile microalgae Coccomyxa melkonianii pH efect screening Nitrate efect Lipid biosynthesis Mathematical modeling ABSTRACT In the present study, the efect of nitrogen manipulation on the growth of the extremophile microalgal strain Coccomyxa melkonianii SCCA 048 was investigated for the frst time to study its ability to produce marketable products, such as lipids. To identify the best strategies for cultivating this alga in large scale systems, the nitrate- and pH-dependent growth kinetics and the corresponding kinetic parameters were frst evaluated in a multiwell screening. Subsequently, the efects of initial nitrogen concentration on the growth rate, nitrate uptake, as well as the synthesis of lipids and their corresponding quality, were investigated in batch photobioreactors. The experimental results were then successfully interpreted by a simple, albeit novel and exhaustive, mathematical model which takes into account the efects of light intensity, nitrate concentration and pH on the growth and lipid synthesis of this strain. By assessing the pH-dependent kinetics, it was confrmed that Coccomyxa melk- onianii is extremophile as far as pH conditions are concerned. Moreover, the obtained growth rates and lipid productivities were high enough to permit sustainable cultivation at large scale. In particular, a quite interesting lipid content (about 40 %wt) was achieved under nitrogen starvation conditions. The fatty acids obtained by transesterifcation of the extracted lipids might be potentially exploited in diferent industrial sectors. In addi- tion, the proposed model represents a frst step towards the development of a useful tool for the optimization and the design of raceway-type bioreactor where Coccomyxa melkonianii would be cultivated. 1. Introduction Microalgae are currently considered a potential feedstock for the sustainable production of a wide range of consumer goods such as biofuels, nutraceuticals, pharmaceuticals, bioplastics, functional food, lubricants for industrial applications and food for aquaculture systems [1,2]. When compared to traditional crops, microalgae are character- ized by higher photosynthetic efciency and biomass productivity, as well as the capability to grow in non-arable/arid lands by exploiting wastewaters and CO 2 as a source of nutrients. Accordingly, microalgae cultivation may lead to positive side efects related to the reduction of water and atmospheric pollution [3]. https://doi.org/10.1016/j.cej.2018.12.049 ⁎ Corresponding authors at: Interdepartmental Center of Environmental Science and Engineering (CINSA), University of Cagliari, Via San Giorgio 12, 09124 Cagliari, Italy (G. Cao). E-mail addresses: aconcas@crs4.it (A. Concas), giacomo.cao@dimcm.unica.it (G. Cao). Chemical Engineering Journal xxx (xxxx) xxx–xxx 1385-8947/ © 2018 Elsevier B.V. All rights reserved. Please cite this article as: Soru, S., Chemical Engineering Journal, https://doi.org/10.1016/j.cej.2018.12.049