Biochemical composition and antioxidant capacity of marine microalgae Chlorella salina Butcher and Isochrysis maritima Billard and Gayral isolated from Penang coastal waters
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Date
2014-08
Authors
Shahar, Siti Syazwina
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Abstract
Chlorella salina and Isochrysis maritima were successfully isolated, purified and cultured in Conway medium. Morphology and ultra-structures of strains were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Changes in growth profile, analytical analyses, pigments, biochemical compounds as well as fatty acid compositions were investigated during a batch culture growth. C. salina and I. maritima were cultivated in conventional batch culture method with up scaling from 100 mL starter culture to 1 liter experimental culture. Larger scale volume cultures displayed higher biomass concentration (only in I. maritima), higher specific growth rates and faster doubling times. Dry weight, ash free dry weight of both species and moisture content of I. maritima were significantly influenced by growth phase (p<0.05) while total ash content was unaffected. The green algae, C. salina contained both pigments of chlorophyll a and chlorophyll b whereas only chlorophyll a was detected in I. maritima. Protein content in both isolates decreased whereby more carbohydrate and lipid accumulated in C. salina and I. maritima, respectively as culture aged. In total, the proximate biochemical compound of C. salina was found in the sequence where protein had the highest content, followed by carbohydrate and the lowest content was lipid whilst I. maritima had highest protein content followed by lipid and least amount of carbohydrate regardless of the growth phases. A clear define pattern of variations in fatty acid profile was exhibited in the green algae, C. salina with major fatty acids fraction where highest content was PUFA followed by SFA and lowest
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was MUFA throughout the growth phases whereas I. maritima had highest content of SFA followed by PUFA and least amount of MUFA during the exponential phase and subsequently had similar content of PUFA and SFA while MUFA remained as lowest content obtained in the stationary phase. Relative abundance of important PUFA detected in C. salina namely linoleic acid (LA) and α-linolenic acid (ALA) with low occurrence of γ-linolenic acid (GLA) and docohexanoic acid (DHA) while I. maritima relatively high in ALA, GLA and DHA with minor presence of arachidonic acid (ARA) and ecosapentanoic acid (EPA). The potential of these marine microalgae as natural antioxidant source were evaluated using DPPH free radical scavenging test at different extract concentrations. The results showed maximum values of 43.37 ± 2.20% and 11.64 ± 2.61% were achieved during stationary phase at highest concentration (25 mg mL-1) in C. salina and I. maritima, respectively, indicating both strains were weak radical scavenger. The present study provides deeper knowledge and better understanding on growth profiles, variation of nutritional compositions and antioxidant capacity associated with the growth phases of tropical marine microalgae.
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Marine microalgae , Penang coastal waters