Expression of Synthetic Phytoene Synthase Gene to Enhance β-Carotene Production in Scenedesmus sp CPC2

beta-carotene is a valuable pigment abundant in some microalgal species but the low beta-carotene productivity of microalgae has become the major obstacles against its commercialization. This work aims to improve the productivity of algae-based beta-carotene via genetic engineering approaches. First, a synthetic psy gene construct (891 bp) encoding 297 amino acids is expressed in Scenedesmus sp. CPC2 host to enhance the beta-carotene production. The synthetic psy gene is designed by considering the highest consensus of amino acids (i.e., 62% identity) from Chlamydomonas reinhardtii, Dunaliella salina, and Mariella zofingiensis. The original beta-carotene content in wild-type Scenedesmus sp. CPC2 is 10.8 mg g(-1)-cell when grown on BG11 medium under 2% CO2 aeration, 150 mu mol m(-2) s(-1) light intensity and 25 degrees C. After transformation of the psy gene into the microalgal host, the beta-carotene content of the best recombinant strain (i.e., transformant CPC2-4) significantly increased to over 30 mg g(-1)-cell. The optimal production of beta-carotene with the CPC2-4 recombinant strain was achieved when the strain is grown on BG11 medium amended with 0.075 g of MgSO4, giving approximately 3-fold higher beta-carotene content than that of the wild-type strain. The best cellular beta-carotene content obtained (i.e., 31.8 mg g(-1)) is superior to most algae-based beta-carotene production performance reported in the literature.