Long-term reliable culture of a halophilic diatom, Amphora sp. MUR258, in outdoor raceway ponds

Abstract

The microalgal industry as a source of high-value products (i.e. β-carotene, astaxanthin) was established over 50 years ago. However, only a very small number of species have been commercialised. There is a need for new species and new products to expand this industry. The objective of this study was to examine the reliability and productivities of long-term outdoor culture of a newly isolated halophilic diatom, Amphora sp. MUR258 (Bacillariophyceae), in raceway ponds in Perth, Western Australia. The Amphora sp. was grown in outdoor raceway ponds as a semi-continuous culture for about 13 months at a culture salinity between 8.6 and 14.9% (w/v) NaCl. The highest cell density (167 × 104 cells mL−1), specific growth rate (0.29 day−1) and biomass and lipid productivities (24 and 6.8 g m−2 day−1, respectively) were achieved in summer. The annual average of biomass (ash-free dry weight) and lipid productivities was 7 and 2.2 g AFDW m−2 day−1, respectively. Minor contamination by a Navicula sp. was seen during winter, but was not a significant problem. No major protozoan contamination was seen. These results indicate the potential of reliable large-scale cultivation of Amphora sp. MUR258 as a potential source of diatom lipid and/or fucoxanthin.