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Polysaccharide production and antioxidant activity of Pectodictyon cubicum Taft, a mucilaginous microalga

Ferreira J.D.1*, Assunção M.F.G.1, Varejão J.M.T.B.2 and Santos L.M.A.1
  • 1 University of Coimbra, Department of Life Sciences, Portugal
  • 2 Instituto Politécnico de Coimbra, Escola Superior Agrária de Coimbra, Portugal

Microalgae are photosynthetic organisms regarded as a source of raw material to take into account for various branches of industry (Borowitzka, 2013; Pignolet et al, 2013). Microalgal polysaccharides, for example, are a group of carbohydrates with great potential for applications in medicine and nanobiotechnology. The increased interest in this group of molecules by biomedical and chemical researchers is due to their good biocompatibility, biodegradability, nontoxicity, low cost and abundance (Manivasagan & Oh, 2016). Furthermore, microalgae have the ability to withstand the exposure to aquatic environmental stresses, such as high oxygen concentrations and light, that increase cellular levels of oxygen reactive species (ROS), by stimulation of their antioxidant defence mechanisms (Guedes et al, 2013; Nathra et al, 2007). As a consequence, these organisms produce protective compounds, namely carotenoids and phenols, which may be suitable as supplements for human nutrition against the damaging effect of naturally produced ROS (Munir et al, 2013). Pectodictyon cubicum Taft is a poorly studied chlorophyte surrounded by a dense mucilage envelope that forms cubical net-structured mucilaginous colonies (Lang et al, 1987). Based on the high amounts of exopolysaccharide produced to support the live habit, we may question whether some biotechnological potential of this species lies in its mucilage. The studied strain Pectodictyon cubicum ACOI 1651 was isolated from a central lake in the Botanical Garden of Coimbra and is held at the Coimbra Collection of Algae (ACOI). Growth was assessed by dry weigh (DW), for a period of 31 days, under controlled conditions (culture medium M7, air bubbling, at room temperature of 23ºC, an average light intensity of 21.62μmol m-2 s-1 and a photoperiod of 16h: 8h light/dark) and showed a very long exponential phase followed by an immediate decline phase with absence of a stationary phase. The biomass had an increment of 1.34 g/L after that period. The polysaccharide content and antioxidant activity of P. cubicum were evaluated in the exponential and decline growth phases, on days 15 and 30, respectively. Alkaline extraction of the polysaccharides produced was performed and followed by acidic hydrolysis (Okajima-Kaneko, 2007; Pereira et al, 2003). The analysis of the obtained monosaccharides was performed in high pressure liquid chromatography (HPLC). Polysaccharide production was determined as a % DW of biomass. A small difference was noted in both growth phases, with an increase of 6% from day 15 (39%) to day 30 (45%). The identified monosaccharides were mainly arabinose, rhamnose and galactose, commonly found in green algae (Park et al, 2011; Bayona & Garcés, 2013). The most abundant was arabinose with 94.8% and 91% (relative %) at days 15 and 30, respectively. The antioxidant activity of the strain was tested by two methods, ABTS and DPPH (Brand-Williams et al, 1995; Guedes et al, 2013a) and the results compared with extracts obtained from fruits and vegetables. The antioxidant activity inferred by the ABTS method for day 30 (4.85 mg/L equivalent ascorbic acid) was lower than that measured on day 15 (7.85 mg/L equivalent to ascorbic acid), values close to those of fresh carrot (5.98mg/L equivalent to ascorbic acid). However, an opposite tendency was found when antioxidant evaluation was performed by DPPH method, with better antioxidant activity of extracts obtained in 30 days. In conclusion, the strain P. cubicum ACOI 1651 demonstrated a high production of polysaccharides at both times of growth considered, however the increase between them was surprisingly low. This shows that, under the established cultivation conditions, the mucilage production slows down after reaching a maximum value. Regarding the possible biotechnological potential of the strain, alongside with its appreciable antioxidant activity, the composition of monosaccharides is similar to the Arabic gum (Vázquez-Ortíz et al, 2011), indicating application capabilities of P. cubicum mucilage for purposes of thickening, gelling and emulsification.

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Keywords: Microalgae, ACOI, Growth, Polysaccharides, antioxidant activity

Conference: IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016.

Presentation Type: Poster presentation

Topic: Blue Biotechnology

Citation: J.D. F, M.F.G. A, J.M.T.B. V and L.M.A. S (2016). Polysaccharide production and antioxidant activity of Pectodictyon cubicum Taft, a mucilaginous microalga. Front. Mar. Sci. Conference Abstract: IMMR | International Meeting on Marine Research 2016. doi: 10.3389/conf.FMARS.2016.04.00001

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Received: 05 Jul 2016; Published Online: 05 Jul 2016.

* Correspondence: Miss. Ferreira J.D., University of Coimbra, Department of Life Sciences, Coimbra, 3000-456, Portugal, ferreirajoanadias@gmail.com