Enhanced Carotenoid Production in Chlamydomonas reinhardtii by Overexpression of Endogenousand Exogenous Beta-Carotene Ketolase (BKT) Genes

Abstract

Chlamydomonas reinhardtii is a unicellular green alga that can grow heterotrophically by using acetate as a carbon source. Carotenoids are natural pigments with biological activity and color, which have functions such as antioxidant, anti-inflammatory, vision protection, etc., and have high commercial value and prospects. We transformed Chlamydomonas reinhardtii with the BKT genes from Phaffia rhodozyma (PrBKT) and Chlamydomonas reinhardtii (CrBKT) via plasmid vector, and screened out the stable transformed algal strains C18 and P1. Under the condition that the cell density of growth was not affected, the total carotenoid content of C18 and P1 was 2.13-fold and 2.20-fold higher than that of the WT, respectively. CrBKT increased the levels of β-carotene and astaxanthin by 1.84-fold and 1.21-fold, respectively, while PrBKT increased them by 1.11-fold and 1.27-fold, respectively. Transcriptome and metabolome analysis of C18 and P1 showed that the overexpression of CrBKT only up-regulated the transcription level of BKT and LCYE (the gene of lycopene e-cyclase). However, in P1, overexpression of PrBKT also led to the up-regulation of ZDS (the gene of ζ-carotene desaturase) and CHYB (the gene of β-carotene hydroxylase). Metabolome results showed that the relative content of canthaxanthin, an intermediate metabolite of astaxanthin synthesis in C18 and P1, decreased. The overall results indicate that there is a structural difference between CrBKT and PrBKT, and overexpression of PrBKT in Chlamydomonas reinhardtii seems to cause more genes in carotenoid pathway metabolism to be up-regulated.

Enhancing astaxanthin biosynthesis and pathway expansion towards glycosylated C40 carotenoids by Corynebacterium glutamicum

“…1 ). Pathway engineering strategies by overexpressing of the β-carotene ketolase or hydroxylase genes 18 , balancing their expression 19 , translational fusions or modularized complexes of carotenogenesis genes 20 – 22 as well as blocking of competing pathways have been shown to be effective for increasing astaxanthin production 23 . Moreover also bioprocess parameters such as temperature, pH 24 , light 25 and process optimization have been used to enhance astaxanthin production 26 , 27 .…”

Evaluation of Cellular Responses by Chlamydomonas reinhardtii in Media Containing Dairy-Processing Residues Derived from Cheese as Nutrients by Analyzing Cell Growth Activity and Comprehensive Gene Transcription Levels

“…For several decades now, Saccharomyces cerevisiae and Escherichia coli have been representative industrial microorganisms with merits such as safety [16] and capability of modification by genetic engineering [17], resulting in their use as bio-converters for value-added production [18,19]. In recent years, not only these heterotrophic microorganisms but also autotrophic microorganisms including green algae such as Chlamydomonas reinhardtii and Chlorella vulgaris have attracted attention for use as material producers [20][21][22]. These green algal species can be additionally useful as bio-converters because these species can convert inorganic carbon sources such as carbon dioxide and organic carbon sources like acetic acid into useful metabolites [23].…”