Enhancement of Astaxanthin Content in Mixed Culture of Dunaliella sp. and Azospirillum sp. under Light Intensity Treatment

Abstract

Dunaliella sp. is a potential natural source of carotenoid pigments such as as-taxanthin, β-carotene, and lutein. Dunaliella sp. can also accumulate other valu-able products such as glycerol and protein. Another species is Azospirillum sp., which is known as microalgal growth-promoting bacteria. These bacteria are often cultured with microalgae because they contain indole-3-acetic acid, which can significantly increase the growth of microalgae. This study aimed to exam-ine the pigment content in mixed culture of Dunaliella sp. and Azospirillum sp. after being treated with different light intensity treatment. In this study, Dunaliel-la sp. were cultivated by mixing with Azospirillum sp. under light stress. Two treatments were performed at light stress intensity of 3000 and 6000 lx. Light intensity is widely used as an important parameter in cultivation, which can affect the growth and production of microalgal biomass. In addition, spectropho-tometric UV-Vis based measurement was conducted to investigate every single pigment content in all treatments under light stress for eight days. The number of cells, carotenoid pigments, and astaxanthin had increased significantly. Pigments of chlorophyll a and chlorophyll b also significantly increased at lower light treatments. Based on the results, the bacterium Azospirillum sp. and high light intensity significantly increased the growth and cell division of microal-gae. Therefore, the combination of Azospirillum sp. and light stress intensity in microalgae cultivation could increase the growth and pigment of Dunaliella sp.