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Sponge-bacteria may yield food-grade pigments, say researchers

By Stephen Daniells , 18-Feb-2009

Food-grade pigments may be obtained by fermenting bacteria sourced from sponge, according to preliminary studies from India.

Tapping into the growing trend for natural colours for food, researchers from the University of Kerala and the Zoological Survey of India report that exposure of the bacteria to fluorescent light leads to production of a range of carotenoids that could be used as food-grade yellow and red colourants.

The findings are published online in Food Research International.

“Colours play a special role with the food we eat. For example, when confronted with an unattractive colour, the consumer assumes that the food is poor or spoiled,” explained the researchers, led by Selvakumar Dharmaraj.

“Nowadays, fermentative production of food grade pigments particularly carotenoids from microorganisms are available in the market.

“All these facts paved way for the present study in which Streptomyces strains are isolated from marine sponge and assessed for the production of carotenoids, by fermentation, which can be used as food-grade pigments,” they wrote.

According to Leatherhead Food International (LFI), natural red pigments are anthocyanins, betalains, and carotenoids sourced from berries and grapes, red beetroot, and red fruit, vegetables and flowers, respectively.

The key natural compounds responsible for yellow colours available to food scientists include annatto, beta-carotene, lutein, mixed carotenoids, riboflavin, and curcumin, said LFI.

Companies such as Wild and Chr Hansen offer a range of yellow and orange pigments based on carotenoids, for example.

Study details

The researchers isolated Streptomyces strain (AQBWWS1) of white series from the marine sponge Callyspongia diffusa, and fermented the bacteria under fluorescent white light. This lead to production of food-grade carotenoids, including lycopene and “an unidentified pigment”, said the researchers.

The preliminary results need further study, added the researchers, including how such pigments could be mass produced for the international food industry.

“The success of any pigment produced by fermentation depends upon its acceptability in the market, regulatory approval, and the size of the capital investment required in bringing the product to market,” wrote the researchers.

“The sponge-associated Streptomyces isolate (AQBWWS1), which on fluorescent light exposure, exhibited carotenoid production.

“If these symbiotic Streptomyces strains, from which secondary metabolites like carotenoids are derived, can be cultured under light, these could be used for mass production of pigments which can then be incorporated as food colourant and also as a feed additive for the growth and colouration of ornamental fishes,” concluded the researchers.

Source: Food Research InternationalPublished online ahead of print, doi: 10.1016/j.foodres.2009.02.006“Food-grade pigments from Streptomyces sp. isolated from the marine sponge Callyspongia diffusa”Authors: S. Dharmaraj, B. Ashokkumar, K. Dhevendaran.

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