Biotechnology Advances 37 (2019) 193–222 Contents lists available at ScienceDirect Biotechnology Advances journal homepage: www.elsevier.com/locate/biotechadv Research review paper New horizons in culture and valorization of red microalgae T Clement Gaignarda,1, Nesrine Gargoucha,b,1, Pascal Dubessaya, Cedric Delattrea, ⁎ Guillaume Pierrea, Celine Larochea, Imen Fendrib, Slim Abdelkafic, Philippe Michauda, a CNRS, SIGMA Clermont, Institut Pascal, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France b Laboratoire de Biotechnologies Végétales appliquées à l'amélioration des cultures, Life Sciences Department, Faculty of Sciences of Sfax, University of Sfax, Sfax, Tunisia c Unité de Biotechnologie des Algues, Biological Engineering Department, National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia ARTICLE INFO ABSTRACT Keywords: Research on marine microalgae has been abundantly published and patented these last years leading to the Red microalgae production and/or the characterization of some biomolecules such as pigments, proteins, enzymes, biofuels, Polysaccharides polyunsaturated fatty acids, enzymes and hydrocolloids. This literature focusing on metabolic pathways, Pigments structural characterization of biomolecules, taxonomy, optimization of culture conditions, biorefinery and Porphyridium downstream process is often optimistic considering the valorization of these biocompounds. However, the ac- Rhodella cumulation of knowledge associated with the development of processes and technologies for biomass production and its treatment has sometimes led to success in the commercial arena. In the history of the microalgae market, red marine microalgae are well positioned particularly for applications in the field of high value pigment and hydrocolloid productions. This review aims to establish the state of the art of the diversity of red marine mi- croalgae, the advances in characterization of their metabolites and the developments of bioprocesses to produce this biomass. 1. Introduction mixotrophic even if they are mainly photoautotrophic organisms. Their systemic classification is based on their pigment composition leading to Microalgae constitute a diverse group of eukaryote photo- nine classes in which the main groups are Phaeophyceae, Chlor- autotrophic single cell-organisms present in many ecosystems including ophyceae, Pyrrophyceae, Bacillariophyceae, Chrysophyceae and Rho- terrestrial, aquatic and airborne environments (Flechtner, 2007; dophyceae or red microalgae. It has been estimated that about Rajvanshi and Sharma, 2012; Tesson et al., 2016; William and Laurens, 200,000–800,000 species exist (including Cyanobacteria) of which 2010). They are able to live in harsh conditions (Lewis and Flechtner, 50,000 species are described (Guiry, 2012; Richmond, 2004; Norton 2002; Pushkareva et al., 2016) and use solar energy, water, and in- et al., 1996). The large diversity of microalgae species is correlated with organic nutrients to reduce CO2 into complex organic compounds. a large variety of enzymes and metabolites including amino acids, Some of them have also the ability to use some organic carbon dividing peptides, proteins, carbohydrates (notably complex poly- and oligo- their metabolism into three types: photoautotrophic, heterotrophic and saccharides), polyunsaturated fatty acids (PUFAs), carotenoids, sterols, Abbreviations: AA, Arachidonic acid; ACP, Acyl-transporter-protein; APC, Allophycocyanin; ATP, Adenosine triphosphate; B-PE, B-Phycoerythrin; BPS, Bound polysaccharide; CA, Carbonic anhydrase; CCM, CO2 concentrating mechanism; Chl a, Chlorophyll a; Chl b, Chlorophyll b; Chl c, Chlorophyll c; Chl d, Chlorophyll d; Ci, Inorganic carbon; C-PC, C-Phycocyanin; C-PE, C-Phycoerythrin; DHA, Docohexaenoic acid; DNA, Deoxyribonucleic acid; DW, Dry weight; EMP, Embden- Meyerhof pathway; EPA, Eicosapentaenoic acid; FACS, Fluorescence-activated cell sorting; FRET, Fluorescence resonance energy transfert; Gc, Compensation ir- radiance; GLA, γ-linolenic acid; GOGAT, Glutamate synthase; GS, Glutamine synthetase; Gs, Saturation point; IPS, Intracellular polysaccharide; Ma, Million years ago; MW, Molecular weight; MWCO, Molecular weight cut off; NADH, Nicotinamide adenine dinucleotide; NADPH, Nicotinamide adenine dinucleotide phosphate; Ni, Nitrite reductase; NR, Nitrate reductase; PAR, Photosynthetic active radiation; PBR, Photobioreactor; PC, Phycocyanin; PE, Phycoerythrin; PEC, Phycoerythrocyanin; PES, Polyethersulfone; PEG, poly(ethylene glycol); PFD, Photon flux density; PPP, Pentose phosphate pathway; PS, Polysaccharide; PUFA, Polyunsaturated fattyacid; PVC, Polyvinyl chloride; q0, incident light flux; RNA, Ribonucleic acid; R-PC, R-Phycocyanin; R-PE, R-Phycoerythrin; RPS, Released polysaccharide; RuBisCo, Ribulose-1,5-bisphosphate carboxylase/oxygenase; sPS, Sulphated polysaccharide; TAG, Triacylglyceride; TCA, Tricarboxilic acid; TUF, Tangential ultrafiltration; VLDL, Very low density lipoprotein ⁎ Corresponding author. E-mail address: [email protected] (P. Michaud). 1 C. Gaignard and N. Gargouch contributed equally to this work. https://doi.org/10.1016/j.biotechadv.2018.11.014 Received 18 May 2018; Received in revised form 26 November 2018; Accepted 26 November 2018 Available online 28 November 2018 0734-9750/ © 2018 Elsevier Inc. All rights reserved. C. Gaignard et al. Biotechnology Advances 37 (2019) 193–222 saturated lipids and others. The industrial exploitation of these meta- called blue-green algae) and eukaryotic microorganisms. The eu- bolites for the sustainable production of biomolecules, biofuel, food or karyotic microalgae emerged phylogenetically later than Cyanobacteria feed is at its early stages (Pignolet et al., 2013). Indeed, the maximum and resulted from succession of two independent endosymbiosis steps, theoric photosynthetic efficiency of microalgae in terms of conversion the first giving rise to the red (Rhodophyceae) and green algae of light energy into biomass energy is between 3 and 10% against (Chlorophyceae) and the second leading to the Dinoflagellates, Cryp- 0.2–6% for C3 and C4 plants (Barsanti and Gualtieri, 2018). How- tophytes, Euglenida and Heterokont groups, consisting of brown algae ever, < 100 genera of microalgae have been cultivated at the labora- (Phaeophyceae), yellow-green algae (Xanthophyceae), golden algae tory scale and no > 10 were produced in an industrial context. They (Chrysophyceae) and diatoms (Baciliarophyceae). include Chlorella, Nannochloropsis, Isochrysis, Muriellopsis, Odontella, The red algae (macro- and microalgae) are one of the most distinct Dunaliella, Haematococcus, Porphyridium or Rhodella genera which are eukaryotic groups whose origin resulted from the acquisition of a exploited for food/feed production (nutraceutical industries, poultry plastid from a cyanobacterium through primary endosymbiosis ap- aquaculture and nutrients), pharmaceutical and ecological applications proximately 1600 Ma. Most of the Rhodophyta live in marine en- (bioenergy, water treatment, CO2 emissions remediation, chemicals, vironments and are macroscopic (macroalgae). Their diversity is esti- materials, pharmaceuticals care) and also in the cosmetic industry mated around 700 genera and > 10,000 species (Kraft and (personal care) (Barsanti and Gualtieri, 2018; Liu et al., 2016; Vigani Woelkerling, 1990; Silva and Moe, 1997). They constitute a mono- et al., 2015). The producers clearly focus on niche markets for high phyletic eukaryotic group whose member's affiliation is based on phy- value microalgal products capable of counterbalancing the production logenetic analysis of nuclear, plastid and mitochondrial genes (Burger costs as well as biomass treatments. Large markets like those related to et al., 1999; Freshwater et al., 1994; Ragan et al., 1994). In the 1970s the production of biofuels are not currently economically viable and the and 1980s, morphology and molecular markers (16S, 18S, SSU and new challenge is to propose an innovative framework for microalgal rbcl) based on taxonomy led to classification of Rhodophyceae into biorefinery. So, special attention has been paid to obtaining biofuel and subclasses including the Bangiophycidae and the Florideophycidae high value biomolecules via systems integration and engineering (Zhu, (Dixon, 1973; Gabrielson et al., 1985; Garbary and Gabrielson, 1990). 2015). More recently, the classification of red algae was revised and anew Among the microalgae exploited at the industrial scale, red micro- taxonomic model was proposed by Saunders and Hommersand (2004), algae (Rhodophyta) such as those belonging to the genera Porphyridium and Yoon et al. (2006). In their classification scheme (Table 1), Saun- and Rhodella are of increasing interest as a source of valuable com- ders and Hommersand proposed, next to the phylum Rhodophyta, a pounds such as extracellular polysaccharides, phycobiliproteins and new phylum called Cyanidiophyta, including a single class named Cy- long chain PUFAs (Guihéneuf and Stengel, 2015; Pignolet et al., 2013). anidiophyceae. The phylum Rhodophyta was for its part divided in Among the phycobiliproteins which constitute the major accessory three subphyla (Rhodellophytina, Metarhodophytina and Eur- light-harvesting pigments, the phycoerythrin (PE, 540–570 nm) gives a hodophytina) where four classes (Rhodellophyceae, Compsopogono- pink/red color to the microalgae. Phycocyanin (PC, 610–620 nm) and phyceae, Bangiophyceae and Florideophyceae) were identified. In allophycocyanin (APC, 650–655