New report of Halamphora subtropica (Bacillariophyta) from the Strait of Malacca and its growth and biochemical characterisation under nutrient deprivation

Abstract

A symmetrical bi-raphid pennate diatom isolated from tropical coastal waters in the Strait of Malacca was identified as Halamphora subtropica, which is significant given that the distribution of this species was until now limited to subtropical waters in western Atlantic Ocean and western Pacific Ocean, hence its etymology. To assess its potential as biodiesel feedstock, the alga was cultivated, and its growth and biochemical composition compared under nutrient replete and nutrient (N, P, Si) deprived conditions. The growth of H. subtropica was more suppressed under N- conditions but was less affected under P- and/or Si- conditions. The highest biomass and lipid productivity of 19.7 ± 0.8 and 4.0 ± 0.4 mg L−1 day −1 respectively, were achieved under nutrient replete condition followed by P- and Si- conditions. Cells grown in nutrient-deprived media contain higher monounsaturated fatty acids while higher polyunsaturated fatty acids were observed in the complete medium. Palmitic acid, palmitoleic acid and stearic acid accounted for over 60% of the total fatty acids. The strain used in this study showed comparable values of biomass productivity, lipid productivity and lipid content (≈30% dw) to diatom strains reported previously, suggesting that H. subtropica may be considered as a candidate for biofuel feedstock. These results contribute additional evidence on the potential of using tropical marine diatom strains as feedstock for biofuel, given that existing literature tend to focus on subtropical or temperate strains.