Cancer Lett. The in vitro synthesis of soluble -1,3-glucans could be an alternative to the hydrolysis approach. 2016, Gissibl et al. doi: 10.1371/journal.pone.0191462, Takeda, T., Nakano, Y., Takahashi, M., Konno, N., Sakamoto, Y., Arashida, R., et al. doi: 10.3389/fenrg.2016.00036, Andreani, L., and Rocha, J.D. However, an in-depth proteomic analysis recently revealed a unique pathway for arginine biosynthesis in E. gracilis, which is independent from the urea cycle commonly utilised by other eukaryotic organisms (Hasan et al., 2017). Phycol. Life Sci. The promising future of microalgae: current status, challenges, and optimization of a sustainable and renewable industry for biofuels, feed, and other products. saccharophila. Anti-fibrotic effect of paramylon nanofibers from the WZSL mutant of Euglena gracilis on liver damage induced by CCl4 in mice. Microbiol. Furthermore, substantial research has been performed to improve the WE yields specifically. Increased synthesis of -tocopherol, paramylon and tyrosine by Euglena gracilis under conditions of high biomass production. Accordingly, the cells synthesise FAs, fatty alcohols (FAlcs) and ultimately WEs in larger quantities from paramylon under oxygen-limiting conditions (Inui et al., 1984; Tucci et al., 2010; Furuhashi et al., 2015; Yoshida et al., 2016). Eng. Fatty acid synthesis in mitochondria of Euglena gracilis. doi: 10.1016/0014-4827(64)90071-0, Marechal, L.R. Suppression of DYRK ortholog expression affects wax ester fermentation in Euglena gracilis. (1964). It has secondary chloroplasts, and is a mixotroph able to feed by photosynthesis or phagocytosis. 2, 113. Biological, and Environmental Sciences, Faculty of Agriculture, Tottori . Hepatogastroenterology 56, 547550. (2015). Univ. 64, 817. PLoS ONE 13, 117. doi: 10.1080/10408398.2016.1160362, Yadavalli, R., Rao, C.S., Rao, R.S., and Potumarthi, R. (2014). For example, HT growth in a medium supplemented with external nitrogen (ammonium) has resulted in the production of cell mass with a protein content of close to 0.7 g/g DW, whereas PT cultivation maximally yields 0.5 g/g DW (Chae et al., 2006; Rodrguez-Zavala et al., 2010). doi: 10.1111/j.1440-1835.2006.00416.x, Ramos, M.J., Fernndez, C.M., Casas, A., Rodrguez, L., and Prez, . Biotechnol. 18, 10171029. doi: 10.1016/j.bbrc.2017.09.167, Nakashima, A., Yamada, K., Iwata, O., Sugimoto, R., Atsuji, K., Ogawa, T., et al. J. Vet. Food Chem. They also act as a dietary fibre and have been shown to lower blood cholesterol levels (Nakashima et al., 2018b). Phycol. doi: 10.1111/and.13088, Al Abdallah, Q., Nixon, B.T., and Fortwendel, J.R. (2016). All authors listed have made a direct and intellectual contribution to the work and approved it for publication. Ferment. 494, 379383. 21, 114. Med. Immunomodulation and anti-cancer activity of polysaccharide-protein complexes. J. Microbiol. Carbohydrate Polymers 196, 339347. J. Clin. There are several factors influencing -tocopherol levels in E. gracilis, for example, cultivation under light conditions or the addition of ethanol to the medium have been shown to increase -tocopherol production (Table 1) (Kusmic et al., 1998; Fujita et al., 2008). doi: 10.1038/s41598-017-14077-6, Torihara, K., and Kishimoto, N. (2015). 13, 5965. (2010). Algal Res. In the absence of complete genetic information, transcriptomic and proteomic studies have provided valuable insights into the complex metabolic pathways of E. gracilis and their regulation under different growth conditions (O'Neill et al., 2015b; Yoshida et al., 2016; Hasan et al., 2017). However, the actual yields observed outdoors were much lower and the factors that were responsible for the discrepancy have not been reported (Suzuki, 2017). (2018). a platform for investigating the contributions of E. gracilis and its relatives to the biosphere. The unicellular phototrophic protist E. gracilis is ubiquitous in most freshwater biotopes. doi: 10.1016/j.fsi.2018.04.003, Yamane, Y.-,I., Utsunomiya, T., Watanabe, M., and Sasaki, K. (2001). Catalytic cracking of wax esters extracted from Euglena gracilis for hydrocarbon fuel production. Acta (BBA) Lipids Lipid Metab. For example, when preneoplastic aberrant crypt foci (marker for colon cancer risk) were induced in the colon of mice by 1,2-dimethylhydrazine treatment, the subsequent inclusion of 2% (w/w) paramylon into their diet reduced the development of colon cancer by 50% (Bird, 1995; Watanabe et al., 2013). Fuel 80, 747756. Both - and -tocopherol are, amongst - and -, the major forms of dietary vitamin E. The -form is one of the most abundant lipophilic antioxidants and considered more important for mammalian physiology. doi: 10.1016/j.fsi.2012.04.009, Sonck, E., Stuyven, E., Goddeeris, B., and Cox, E. (2010). Euglena Gracilis is one of the microalgae that has the most potential in helping humanity reach the 5 F's goal. -1,3-glucan chain (~700 n 3,000) (Miyatake and Kitaoka, 1983; Koizumi et al., 1993; Barsanti et al., 2011). Another way to produce biogas consisting mostly of methane from microalgal biomass is through anaerobic digestion by a consortium of microorganisms. Identifying what control mechanisms make E. gracilis so efficient in producing -tocopherol could lead to strategies for the modification of higher plants to increase their -tocopherol yields. Multi-stage Process for Production of Immune Modulator. Nutr. (2013). For example, expression of the Synechococcus elongatus PCC 7942 fructose-1,6-/sedoheptulose-1,7-bisphosphatase gene in E. gracilis chloroplasts was shown to significantly enhance its photosynthetic activity, as well as the paramylon yield (by almost 2-fold), the WE yield under anaerobic conditions (~100-fold) and the biomass yield (~2-fold) (Ogawa et al., 2015). For example, Levine et al. Biochim. doi: 10.1292/jvms.71.885, Sumida, S., Ehara, T., Osafune, T., and Hase, E. (1987). 57, 37033714. As another target for a metabolic engineering approach, trans-2-enoyl-CoA reductase has been identified as a potentially rate-limiting enzyme in the FA synthesis pathway of E. gracilis (Inui et al., 2017). doi: 10.1016/j.algal.2018.08.007, Traber, M.G. doi: 10.1007/s00449-015-1363-1. Biotechnol. (2010). J. Biol. Phycol. Attempts to enhance E. gracilis biomass production under PT conditions, for example with the use of a photobioreactor, resulted in maximum titres similar to those of shake flask cultures, which are several times lower than those of some microalgal species grown under closed PT conditions (Table 1) (Richmond et al., 2003; Chae et al., 2006; Hasan et al., 2017). doi: 10.1016/S0016-2361(00)00142-3, Maxwell, J.R., Douglas, A.G., Eglinton, G., and McCormick, A. This enzyme converts -tocopherol to -tocopherol using S-adenosyl methionine (SAM) as the methyl group donor and also shows promiscuity towards - and -tocopherol (Shigeoka et al., 1992). Recent insights into the complex metabolism of E. gracilis have highlighted unique metabolic pathways, which could provide new leads for product enhancement by genetic modification of the organism. 6, 8493. 11, 28082820. The direct contribution to prey capture represents a novel function . Lytic polysaccharide monooxygenases: the microbial power tool for lignocellulose degradation. Method for Production of Euglena Containing Wax Ester at High Content, and Method for Production of Wax Ester. as a suitable source of lipids for potential use as biofuel and sustainable wastewater treatment. Omega-3 fatty acid biochemistry: perspectives from human nutrition. Biotechnol. doi: 10.4172/2167-7972.1000102, Gissibl, A., Care, A., Parker, L.M., Iqbal, S., Hobba, G., Nevalainen, H., et al. Microalgae can accumulate large quantities of proteins intracellularly and therefore represent an attractive alternative to more traditional sources of dietary protein like meat and fish (Henchion et al., 2017; Ritala et al., 2017). BioSyst. ATCC 31749 by addition of low-polyphosphates. doi: 10.2965/jwet.2015.195, Tossavainen, M., Katyal Chopra, N., Kostia, S., Valkonen, K., Sharma, A.K., Sharma, S., et al. Am. 13, 10781082. It should be noted that ascorbate production by E. gracilis has not attracted much attention, probably because consumption of just 100 to 200 mL of juice from citrus fruits like oranges (Table 1) is enough to fulfil the daily recommended intake of adults (75 and 90 mg for females and males, respectively) (Grosso et al., 2013; US Department of Agriculture., 2018). Nutr. doi: 10.1186/s12864-016-2540-6, Yu, L., Wu, J.-R., Liu, J., Zhan, X., Zheng, Z., and Lin, C.-C. (2011). Received: 28 December 2018; Accepted: 29 April 2019; Published: 15 May 2019. Production of paramylon, a -1,3-glucan, by heterotrophic cultivation of Euglena gracilis on potato liquor. This increase could be a response to ROS generated in the chloroplasts or in the mitochondria. Euglena cells contain bio-compounds like Paramylon (-glucan) which enhances the immune system, helps remove undesirable substances like fats and cholesterol, and also reduces the level of uric acid in the blood. BMC Plant Biol. (2013). BMC Genomics 17, 110. Front. Adv. Nippon Nogeikagaku Kaishi 51, 483488. 343, 1018. antek, B., Felski, M., Friehs, K., Lotz, M., and Flaschel, E. (2010). However, unlike higher plants, E. gracilis produces almost exclusively the -form of tocopherol (Shigeoka et al., 1986; O'Neill et al., 2015b; Fritsche et al., 2017; Hasan et al., 2017). The enzymatic conversion of major algal and cyanobacterial carbohydrates to bioethanol. Oral delivery and gastrointestinal absorption of soluble glucans stimulate increased resistance to infectious challenge. 185186, 922. Biotechnol. Beneragama) Curr. 35, 5868. E. gracilis has been a popular model organism and of considerable biotechnological interest, but the absence of a gene catalogue has hampered both basic research and translational efforts. Implications for the recognition of fungi by innate immunity. Isolation of a 5 desaturase gene from Euglena gracilis and functional dissection of its HPGG and HDASH motifs. Eng. doi: 10.1016/j.biortech.2005.02.037, Chen, C.-Y., Zhao, X.-Q., Yen, H.-W., Ho, S.-H., Cheng, C.-L., Lee, D.-J., et al. . Creation of straight-chain cationic polysaccharide-based bile salt sequestrants made from euglenoid -1,3-glucan as potential antidiabetic agents. One of the highest paramylon titres reported (16 g/L culture) was obtained in a repeated-batch cultivation under HT conditions in the dark (Table 1), using a medium supplemented with potato liquor, vitamins, and a high concentration of glucose (30 g/L) (antek et al., 2012; Grimm et al., 2015). doi: 10.1016/j.algal.2018.11.022, Kim, D., Filtz, M.R., and Proteau, P.J. doi: 10.1186/s12934-018-0879-x, Khatiwada, B., Kautto, L., Sunna, A., Sun, A., and Nevalainen, H. (2019). USDA National Nutrient Database for Standard Reference. A comprehensive assessment of the biosynthetic pathways of ascorbate, -tocopherol and free amino acids in Euglena gracilis var. doi: 10.1002/mnfr.201100230, Williams, R.R., and Cline, J.K. (1936). Automated solid-phase synthesis of oligosaccharides. 58, 532538. doi: 10.1023/a:1008187514624, Barsanti, L., and Gualtieri, P. (2018). Industrial potential of Euglena gracilis. Alternatively, conventional mutagenesis could be used to generate 'natural' mutant strains with desired traits, a process which is generally not considered GM. Engineering solutions for open microalgae mass cultivation and realistic indoor simulation of outdoor environments. de Oliveira, M.A.C.L., Monteiro, M.P.C., Robbs, P.G., and Leite, S. (1999). Algae need their vitamins. 245, 274282. (2014). Advanced aviation fuels: a look ahead via a historical perspective. Biomol. -glucan in foods and its physiological functions. (2015). 61, 207212. However, local legal regulations could prevent (outdoor) cultivation of genetically modified E. gracilis strains (Beacham et al., 2017). Accordingly, the supplementation of both vitamins, produced either by chemical synthesis (thiamine) or extracted from bacterial sources (cobalamin), would be a factor in a scaled-up E. gracilis cultivation and contributing to the overall costs of the process (Williams and Cline, 1936; Fang et al., 2017). 293, 28652876. Influence of fatty acid composition of raw materials on biodiesel properties. Carbohydrate Polymers 93, 499505. doi: 10.1016/j.algal.2018.02.001, Barsanti, L., Passarelli, V., Evangelista, V., Frassanito, A.M., and Gualtieri, P. (2011). 304, 508514. Rep. 28, 457466. Importantly, animal and in vitro studies have shown an excellent digestibility of protein derived from E. gracilis biomass (Hosotani and Kitaoka, 1977). doi: 10.1007/s10811-013-9979-5, Malkoff, D.B., and Buetow, D.E. Food Res. doi: 10.1080/00021369.1986.10867518, Shigeoka, S., Toshio, O., Yoshihisa, N., and Shozaburo, K. (1987). Chloroplast transformation in Euglena gracilis: splicing of a group III twintron transcribed from a transgenic psbK operon. (2011). Algal Res. (Table 1) (de Oliveira et al., 1999; Tokuoglu and nal, 2003; Ramazanov and Ramazanov, 2006;Rodrguez-Zavala et al., 2010). (2009). 52, 203210. (2006). Algae acquire vitamin B12 through a symbiotic relationship with bacteria. Structure. Paramylon, a -1,3-glucan storage polysaccharide derived from Euglena gracilis, has various health benefits, such as anti-obesity effects and modulation of immune function.However, whether paramylon intake affects the circadian clock remains unknown. However, there are a number of prerequisites for open PT cultivation, including the availability of at least 3,000 ha of usable land area, 3 h of average sunlight per day, 500 mm annual rainfall and a tropical/dry/temperate climate. ( 1936 ) its relatives to the biosphere Cox, E. ( 1987 ) hydrolysis approach innate immunity capture a! 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