Potential saffron substitute discovered

Saffron can bring a distinctive colour, aroma and taste to many food industry applications but it is also one of the world’s most expensive spices to produce. Obtained from the stigma of Crocus sativus flowers, it takes around 150,000–200,000 flowers to produce one kilogram of saffron. Now, KAUST researchers have found an alternative to saffron’s active ingredient using a common garden plant.

The colour of saffron comes from crocins: water-soluble pigments derived from carotenoids by a process that is catalysed by enzymes known as carotenoid cleavage dioxygenases (CCDs). Crocins are said to have therapeutic potential and they also have an important role as natural food colourants.

The researchers have now identified an efficient carotenoid cleavage dioxygenase enzyme from Gardenia jasminoides that produces the crocin precursor crocetin dialdehyde. They have also established a system for investigating CCD enzymatic activity in plants and developed a multigene engineering approach for sustainable biotechnological production of crocins in plant tissues.

“The enzyme we have identified and the multigene engineering strategy could be used to establish a sustainable plant cell factory for crocin production in tissue culture of different plant species,” said lead author of the study Xiongie Zheng.

“Our biotechnological approach can also be used on crops, such as rice, to develop crocin-rich functional food.”

Team leader Salim Al-Babili said the study paves the way for efficient biotechnological production of crocins and other high-value compounds derived from carotenoids (apocarotenoids) as pharmaceuticals in green tissues as well as other starch-rich plant organs. It also highlights the contribution of functional diversification among CCD genes to the independent evolution of alternative apocarotenoid biosynthesis routes in different plants.

“Most of our knowledge about CCD enzymatic activity and substrate specificity comes from experiments using E. coli engineered to produce different carotenoids,” he said.

“Functional characterisation in plants, for example by using a transgenic approach such as we have here, is important for deducing the role of CCDs in carotenoid metabolism and unravelling their real contribution to the carotenoid/apocarotenoid pattern.”

The platform technology could be used to produce other important carotenoid-derived compounds, including widely used scents and colourants.

“It could be used to produce safranal and picrocrocin, for example, which give rise to the taste and characteristic aroma of saffron. These could be used as flavour additives and they also have a bioactive potential awaiting exploration,” Zheng added.

The findings have been published in the Plant Biotechnology Journal.

Image credit: iStock.com/Vingeran