Optimization of β-carotene production by an indigenous isolate of Dunaliella salina under salinity-gradient stress

Dunaliella salina has significant industrial aspects, especially for the accumulation of high amounts of β-carotene, which is the main natural source in aquatic food webs. The first step of commercial production is accurate identification owing to phenotypic plasticity in the genus Dunaliella and lack of rigid cell wall. In this study, D. salina was isolated from Sirjan Kafe Namak of Iran when algal bloom had occurred and then identified based on morphological and molecular properties. Morphological characteristics bore a close resemblance to the species D. salina, including cell size, cup-shaped chloroplast, large basal pyrenoid, and stigma position. Moreover, phylogenetic analysis of internal transcribed spacer (ITS) region (~700 bp) corroborated morphological features by confirming the isolate at the species level. Under five different salinity concentrations, this strain could accumulate β-carotene in the range of 0.51-2.78 μg/mL with optimum growth at 2 M NaCl comparable with reported data for D. salina.