Carotenoids are a large class of pigments usually located
in the thylakoid membranes of the grana in chloroplasts,
in the form of carotenoprotein complexes.
The general structure of carotenoids is that of
aliphatic and aliphatic-alicyclic polyenes with a few
aromatic-polyenes. They are widely distributed in plants
and act as photosynthetic pigments in cells that lack
chlorophyll. They have the same basic structure as
vitamin A, and are converted into vitamin A in animal
livers. More than 300 carotenoids are known and this
number is on the rise.
There are several biochemical functions in which
carotenoids play a role, apart from their well-known role
as photosynthetic pigments. Carotenoids act as blue light
harvesting pigments, protect biological systems from
photodynamic damage and are safe food colorants.
Biotechnological Applications
Carotenoids are used commercially as food colorants, feed supplements, nutraceuticals, and for cosmetic and pharmaceutical purposes. The main dietary sources of carotenoids are fruits and vegetables. Microbial processes are developed for the production of carotenoids using bacterial, fungal, and algal strains (Schmidt- Dannert et al. 2009). The genetically modified Y. lipolytica has been developed and patented as an alternative source of bio-based carotenoids (Groenewald et al. 2014).
The genotoxic and subchronic toxicity potential of b-carotene from Y. lipolytica was determined to support the use of this compound as a food ingredient. The b-carotene administered orally to Sprague Dawley rats for 90 days was considered to be at least 500 mg/kg body weight. Adverse effects were not observed following clinical, clinical pathology, and histopathological evaluations of dosed rats. All results show no significant difference in the safety of the product derived from Y. lipolytica (Grenfell-Lee et al. 2014).
Matthäus et al. produced lycopene in a recombinant Y. lipolytica strain. The codon optimized genes crtB and crtI of Pantoea ananatis were expressed in Y. lipolytica under the control of the TEF1 promoter. The rate limiting genes for isoprenoid biosynthesis in Y. lipolytica, GGS1 and HMG1, were overexpressed to increase the lycopene production. All genes were also expressed in a Y. lipolytica strain with POX1, POX2, POX3, POX4, POX5, POX6, and GUT2 deletions, which led to an increased size of lipid bodies and a further increased lycopene production. Lycopene is mainly located within lipid bodies and increased lipid body formation leads to increased lycopene storage capacity in Y. lipolytica. This yeast produced 16 mg/g lycopene in fed-batch culture (Matthäus et al. 2014).
Anticancer Research
These are one of the major plant pigments in green-yellow vegetables. These includingα-carotene, β-carotene, halocynthiaxanthin, fucoxanthin, β-cryptoxanthin, lactucaxanthin,and lutein are being explored as cancer-preventive agents (Murakami et al. 1996).
