<span style="font-size:15.0pt;mso-bidi-font-family:"Times New Roman";mso-bidi-font-weight: bold" lang="EN-GB">Screening, phenotypic and genotypic identification of β-carotene producing strains of <i style="mso-bidi-font-style:normal">Dunaliella</i> <i style="mso-bidi-font-style:normal">salina</i> from Thailand </span>

Abstract

2198-2216<i style="mso-bidi-font-style: normal">Dunaliella salina is a salt-loving microalga that accumulates high amounts of β-carotene when cultivated under unfavorable conditions. In this study we aimed to screen <span style="mso-bidi-font-weight:bold; mso-bidi-font-style:italic">β-carotene producing strains of D.salina <span style="mso-bidi-font-style: italic">from salt soil samples collected from 19 provinces in the northeastern part of Thailand. For preliminary screening 70 pure isolated strains were screened by using 18S rDNA conserved primers (MA1&MA2), only 15 isolates produced a band (~2100 bp) as that of <i style="mso-bidi-font-style: normal">D.salina.  For the o<span style="mso-bidi-font-style: italic">bservation of β-carotene production, these 15 isolates were grown on agar plate containing modified Ramaraj medium with 1.0 M NaCl under continuous illumination.  After a month only 3 isolates completely turned red. However, by using the banding pattern produced by 18S rDNA primers, the 15 isolates could not be differentiated between the β-carotene and non β-carotene producing strains. Comparing the above results we found that the <span style="mso-bidi-font-style: italic">observation of β-carotene production on agar plate is more easy and suitable method than molecular technique to screen β-carotene producing strains. Morphological characteristics of the 3 screened Thai isolates clearly delineated that it belongs to the genus Dunaliella. ITS-RFLP banding pattern, 18S rDNA, ITS and RuBisCo large subunit (rbcL) sequences were used to confirm at the species level. These results indicated that these 3 isolates are D.salina and were named <i style="mso-bidi-font-style: normal">D.salina strain KU07, D.salina strain KU11 and D.salina strain KU13. Under non-stress conditions these 3 strains had an ability to accumulate β-carotene up to 5.61±0.25, 7.58±0.19 and 6.73±0.32 pg/cell, respectively. </span