Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech Novel photobioreactor design for the culture of Dunaliella tertiolecta – Impact of color in the growth of microalgae José Rebolledo-Oyarce a, ⁎ , José Mejía-López b,c,d , Griselda García b,c , Leonardo Rodríguez-Córdova a , César Sáez-Navarrete a,c,e a Departamento de Ingeniería Química y Bioprocesos, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago, Chile b Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago, Chile c Centro de Investigación en Nanotecnología y Materiales Avanzados CIEN-UC, Facultad de Física, Pontificia Universidad Católica de Chile, Santiago, Chile d Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Santiago, Chile e UC Energy Research Center (CE-UC), Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago, Chile ARTICLE INFO Keywords: D. tertiolecta Tubular photobioreactor Light colors Transference of light Growth model ABSTRACT Microalgae are affected by the amount of light received. This parameter can be controlled by changing the light source and altering the reactor used for their growth. In this study, the effect of different colors of light was analyzed in the growth of Dunaliella tertiolecta, observing that blue lighting systems reached a biomass 10 times superior to the one generated by orange lightning systems. This growth effect was seen in a novel tubular internally illuminated photobioreactor. In this photobioreactor, the blue reactor produced 1.7 times the biomass of the red reactor, with the particularity that the latter showed an oscillating behavior in its growth. From irradiance models, the light dispersion coefficient is higher than the absorption coefficient when using red light. In contrast, with blue light, the value of the scattering coefficient is almost null. 1. Introduction For the last few decades, microalgae have been an object of study due to their ability to produce compounds of high commercial interest, such as biofuels (Leong et al., 2018; Rodionova et al., 2017), β -car- otene, astaxanthins, medicines, biopolymers and nutritive supplements (Borowitzka, 2013; Patel et al., 2017). In addition, these microorgan- isms are used as biofilters to capture industrial CO 2 and NO x from wastewater (Kumar et al., 2016; Markou et al., 2018; Vo et al., 2019a). For the production of these compounds, the microalgae are har- vested from cultivation systems in order to obtain algal biomass. This biomass can be applied different methods of extraction to recover the compounds of interest. These extraction methods are three: physical (drying, sonification, and pulsed electric field), mechanical (bead mil- ling, homogenization) and chemical/biological (acid, base and en- zymes) (Soto-Sierra et al., 2018; Šoštarič et al., 2012; Likozar et al., 2016). In addition to the possibility of extracting high value com- pounds, the biomass can be subjected to chemical process to obtain different compounds, such as bioplastics, ethanol, biohydrogen, among others Patel et al. (2017). However, to produce the different products mentioned, a stable and economically viable biomass production system is necessary, therefore, studies about microalgae have focused on the scaling up of different bioreactors. These bioreactors are divided into two types: open and closed. The first one are open to the environment so the possibility of contamination is high, and the temperature control is low, however, they are very easy to scale up (Adeniyi et al., 2018). In contrast, closed systems allow a high control of the environmental variables, but they are expensive to scale up (Dasgupta et al., 2010). Nevertheless, the closed systems have been emerging as the best reactor design for the production of any type of microalgae (Vo et al., 2019b; Dasgupta et al., 2010). In this category, there are five types: flat plate reactors, column reactor, tubular reactors, soft-frame reactor and hybrid reactor (Vo et al., 2019b; Dasgupta et al., 2010). Flat plate photobioreactors have a large illumination surface area and high biomass productivity rates. In addition, these reactors are easy to scale up (Dasgupta et al., 2010). However, these reactors require a large space available difficult to apply in the industry and causes photoinhibition in cultures generating damage in microalgae (Dasgupta et al., 2010). Column photobioreactors have high gas transfer rates, are compact, easy to scale up. However, due to their design they present a moderate surface area of lighting and high mixing costs, causing the industrial application of these reactors to be slowed down (Dasgupta et al., 2010). https://doi.org/10.1016/j.biortech.2019.121645 Received 11 April 2019; Received in revised form 10 June 2019; Accepted 11 June 2019 ⁎ Corresponding author. E-mail address: jtrebolledo@ing.puc.cl (J. Rebolledo-Oyarce). Bioresource Technology 289 (2019) 121645 Available online 18 June 2019 0960-8524/ © 2019 Elsevier Ltd. All rights reserved. T