Optimization of carotenoids production by Rhodotorula mucilaginosa (MTCC-1403) using agro-industrial waste in bioreactor: A statistical approach Rajan Sharma, Gargi Ghoshal* Dr. S. S. Bhatnagar University Institute of Chemical Engineering and Technology, Panjab University, Chandigarh, India A R T I C L E I N F O Article history: Received 25 October 2019 Received in revised form 30 November 2019 Accepted 1 December 2019 Keywords: Rhodotorula mucilaginosa Agro-industrial waste β-carotene Torularhodin Torulene Antioxidant activity A B S T R A C T Bio-colorants are preferred over synthetic colors as bio-colorants not only impart characteristic color to the food also contain harmless bio-active antioxidant nutrients. The present study was undertaken to investigate the potential of agro-industrial waste (Onion peels, potato skin, mung bean husk and pea pods) for carotenoid production from Rhodotorula mucilaginosa. After screening of appropriate carbon, nitrogen sources from agro-industrial waste, the fermentation conditions (pH, temperature, agitation) were optimized using Response Surface Methodology and optimum conditions were pH 6.1, temperature 25.8  C and agitation 119.6 rpm. Further, to evaluate the effect of aeration on carotenoids synthesis, fermentation was carried out in 3 L bio-reactor under optimum conditions with an air input of 1.0 vvm. Aeration causes elevation of more than 100 mg carotenoids per g of dry biomass. LC-MS of extracted pigment confirmed the presence of some other carotenoids along with β-carotene. The major carotenoid compounds were found from the investigation were torularhodin, β-carotene, and torulene. © 2019 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). 1. Introduction Carotenoids are highly unsaturated isoprene derivatives under the category of tetraterpenoids consisting of eight isoprene units. They contain large C 35 -C 40 polyene chains also known as the backbone of the molecule which is the most crucial feature for the chemical reactivity of the carotenoids towards the free radicals and singlet oxygen molecules [1]. The long carbon chain of alternating single and double bonds is the characteristic feature of carotenoids allowing them to absorb light in the visible range of the spectrum [2]. This feature of carotenoids has significant relevance to eyes with respect to the protection of vision from photo-induced oxidative damage [3]. Along with the use of carotenoids as food colorants, they have also been integrated into nutraceutical bloom especially the β-carotene due to the proven claim of antioxidant properties [4]. Carotenoids, Pro-vitamin A, are one of the most important micronutrients for the proper functioning of eyes and other metabolic processes because their dietary deficiency can result in xerophthalmia, blindness, keratomalacia or in certain cases, death [5]. Most of the natural colors have biologically active chemical compounds known as bioactive compounds or phytochemicals which are categorized as antioxidants. These antioxidants play a very crucial role in the human health as they prevent several types of modern lifestyle diseases such as cancer and cardiovascular diseases (CVDs). This is due to their ability to quench singlet oxygen molecules and scavenge free radicals such as Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) [6]. These free radicals in our body cause oxidative damage of the cells and are responsible for the onset of several degenerative diseases [7–10]. Higher cost of production of natural pigments can be reduced by the use of microorganisms in the synthesis of bio colorants. Among the natural sources, pigment-producing microorganisms are the most efficient candidates to meet the challenges related to the cost and stability. According to Joshi et al. microbial pigments are beneficial over plant pigments due to their availability, higher yield, cost efficiency and convenient down streaming [11]. Similar to plant pigments, colors from microbial sources also possesses anti-inflammatory, antioxidant, anticancer and antimicrobial properties [12]. Carotenoids are primarily produced by several species of yeasts and filamentous fungi. Few bacterial strains along with algae and lichens also produce carotenoids. The variety of colors obtained from microbial sources is far beyond the limits of chemical synthesis and conventional extraction. The important micro- organisms in the synthesis of natural pigments are Monascusroseus producing canthaxanthin (orange, red), Blakesleatrispora, Dunaliella salina, Mucor, Neurospora crassa producing β-carotene * Corresponding author. E-mail address: gargighoshal@yahoo.co.in (G. Ghoshal). https://doi.org/10.1016/j.btre.2019.e00407 2215-017X/© 2019 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Biotechnology Reports 25 (2020) e00407 Contents lists available at ScienceDirect Biotechnology Reports journal homepage: www.else vie r.com/locat e/btre