Table 1.

Comparison of the production titres of various bioproducts between Euglena gracilis and other source organisms or respective concentrations in alternative products.

Bioproduct	Maximum production titre in Euglena gracilis	Alternative source organism or product	Maximum production titre or concentration in alternative source organism or product	References
Dietary protein	0.5 g/g DW; (continous PT cultivation); 0.7 g/g DW; (HT cultivation for 5 d)	Chlorella spp.; Spirulina spp. (grown for 15 d); Beef (lean, cooked); Chicken (cooked); Fish (cooked tuna)	0.6 g/DW; 0.7 g/DW; 0.4 g/g; 0.3 g/g; 0.3 g/g;	(de Oliveira et al., 1999; Tokuşoglu and Ünal, 2003; Chae et al., 2006; Ramazanov and Ramazanov, 2006; Rodríguez-Zavala et al., 2010; US Department of Agriculture., 2018)
Provitamin A (β-carotene)	3.5 mg/g DW or 3.5 mg/L culture; (PT cultivation); 1.4 mg/g DW or 11.4 mg/L culture; (MT cultivation); 3.4 mg/g DW or 71 mg/L culture; (MT/PT fed-batch two-step cultivation for >3 d)	Carrots, dehydrated	0.3 mg/g DW	(Takeyama et al., 1997; US Department of Agriculture., 2018)
Vitamin C (ascorbate)	4 mg/g DW or 8 mg/L culture; (PT cultivation for 1 d or 2 d); Negligible; (HT cultivation); 86.5 mg/L culture; (MT/PT fed-batch two-step cultivation)	Orange juice	50 mg/100 mL	(Shigeoka et al., 1980; Takeyama et al., 1997; Hasan et al., 2017; US Department of Agriculture., 2018)
Vitamin E (α-tocopherol)	2.6 mg/g DW or 8.6 mg/L culture; (PT cultivation for 3 d); mg/g DW or 44.2 mg/L culture; (HT fed-batch cultivation with ethanol for 18.5 d); 3.7 mg/g DW or 40 mg/L culture; (HT batch cultivation with ethanol for 5 d, bleached strain)	Wheat germ oil; Sunflower oil; Olive oil	1.5 mg/g; 0.4 mg/g; 0.1 mg/g	(Ogbonna et al., 1998; Rodríguez-Zavala et al., 2010; Grimm et al., 2015; Hasan et al., 2017; US Department of Agriculture., 2018)
PUFAs (DHA and EPA)	EPA: 5.8 mg/g DW; (MT cultivation for 4 d); DHA: 3.4 mg/g DW; (MT cultivation for 4 d)	Fish oil (e.g. from salmon)	0.2 g/g	(Barsanti et al., 2000; US Department of Agriculture., 2018)
Total lipids and WEs	0.2 g total lipids/g DW; (HT cultivation for 4 d and hypoxic cultivation for 6 d, mutant strain); 0.7 g total lipids/g DW; and 0.6 g WEs/g DW; (Anaerobic HT cultivation for 6 d using an elongase inhibitor)	Botryococcus braunii	0.8 g total lipids/g DW; (mostly FAs or similar compounds)	(Maxwell et al., 1968; Tucci et al., 2010; Yamada et al., 2016; Matos, 2017; Khan et al., 2018)
Paramylon	16 g/L culture; (HT repeated-batch cultivation for 17 d)	Agrobacterium sp. (grown for 3 d)	30 g/L culture of curdlan; (β-1,3-glucan)	(Yu et al., 2011; Šantek et al., 2012; Grimm et al., 2015)
Biogas (produced by anaerobic digestion)	650 mL/g DW; (after PT cultivation for 10 d); 800 mL/g DW; (after MT cultivation for 4 d)	Chaetomorpha litorea; Chlamydomonas reinhardtii; Durvillaea antarctica; Macrocystis pyrifera; Scenedesmus obliquus	80 mL/g DW; 590 mL/g DW; 180 mL/g DW; 180 mL/g DW; 290 mL/g DW	(Behera et al., 2014; Grimm et al., 2015)
Biomass	2–3 g DW/L culture; (PT cultivation for 3 d, shake flask); 12–13 g DW/L culture; (HT cultivation for 2 d, shake-flask); 23 g DW/L culture; (HT repeated-batch cultivation for 17 d, 5 L bioreactor); 48 g DW/L culture; (HT fed-batch cultivation for 7.6 d, 2 L bioreactor)	Nannochloropsis sp.; Chlorella sp.; Crypthecodinium cohnii	≥12 g/L culture; (PT cultivation, photobioreactor); 166 g/L culture; (HT fed-batch cultivation for 2.5 d, 6 L bioreactor); 109 g/L culture; (HT fed-batch cultivation for 16.7 d, 2 L bioreactor)	(Ogbonna et al., 1998, 2002; Richmond et al., 2003; Bumbak et al., 2011; Šantek et al., 2012; Grimm et al., 2015; Hasan et al., 2017)

DHA, docosahexaenoic acid; DW, dry weight; EPA, eicosapentaenoic acid; FA, fatty acid; HT, heterotrophic; MT, mixotrophic; PT, photoautotrophic; PUFA, polyunsaturated FA; WE, wax ester.