Identification of carotenoids biosynthesis pathway in Schizochytrium sp. and utilization in astaxanthin biosynthesis.

Carotenoids, an important kind of natural pigments with great potential commercial value, have been widely used in nutrition and health care, cosmetics and aquaculture industries. Schizochytrium sp. is a potential cell factory for lipid nutrition chemicals production including docosahexaenoic acid and carotenoids. The purpose of this study is to mine and identify the carotenoid biosynthesis genes in Schizochytrium sp. Firstly, based on the genomic information of Schizochytrium sp., we obtained the gene sequences of a trifunctional enzyme (CrtIBY), carotene hydroxylase (CrtZ) and carotene ketolase (CrtO) in carotenoids biosynthesis pathway by bioinformatics analysis. Subsequently, using the lycopene-producing E. coli as the host, 22.77 ug/L of β-carotene and 44.31 ug/L of zeaxanthin were synthesized by overexpression of CrtIBY and further co-expression with CrtZ from Schizochytrium sp. After that, 54.78 ug/L of astaxanthin was synthesized using hydroxylase and ketonase from Haematococcus pluvialis. The key enzymes for carotenoids biosynthesis identified in this study is of great significance for further understanding the metabolic mechanism in Schizochytrium sp, which could also provide the functional elements and theoretical support for astaxanthin production.