Microorganisms as sources of biobased colorants. Going deep into the rainbow of colorful fungi, yeasts, microalgae and bacteria
Résumé
Ingredients derived from microbial fermentation or extracted from microalgae are steadily gaining ground in the food industries (the food industry being taken here as an example of industrial application, among many others). Thickening or gelling agents (e.g. polysaccharides such as xanthan, curdlan, gellan), flavour enhancers (yeast hydrolysate, monosodium glutamate), polyunsaturated fatty acids (PUFAs), flavour compounds (gamma-decalactone, diacetyl, methyl-ketones), vitamins, essential amino acids, and acidulants (lactic acid, citric acid) are some examples illustrating this trend of the biobased economy. Efforts have been made and continue to be done in order to reduce the production costs of pigments produced by algal ponds and microbial fermentation, since synthetic pigments or those extracted from natural plant sources can often be produced more economically. The successful marketing of natural pigments such as -carotene, lutein, and astaxanthin derived from microalgae (i.e. non-conventional sources) or extracted from flowering plants (conventional sources), both as food colorants and nutritional supplements, reflects the presence and importance of niche markets in which consumers are willing to pay a premium for ‘natural healthy ingredients’. Among other non-conventional sources, filamentous fungi and bacteria are known to produce an extraordinary range of pigments that include several chemical classes such as carotenoids, melanins, azaphilones, flavins, phenazines, quinones, and more specifically, monascins, violacein, and indigo. The success of any class of pigment produced by fermentation depends on its acceptance by the consumers, regulatory approval, and the capital investment required bringing the product onto the market. Twenty years ago, influential representatives from food industry expressed doubts about the successful commercialization of microalgae-derived and fermented food grade pigments due to the high investment required for open ponds, photo-bioreactors and fermentation facilities, and the extensive and lengthy toxicity studies required by the regulatory authorities. Poor public perception of fungal-derived products for food use had also to be taken into account. Nowadays, some microbial and algal food grade pigments obtained by fermentation are existing on the market worldwide. Among them, fungal Monascus pigments, Arpink red™ (now Natural Red™) produced by Penicillium oxalicum, microalgal phycocyanin from Arthrospira (Spirulina) platensis, riboflavin from the mold fungus Ashbya gossypii, lycopene and -carotene from the tropical mold Blakeslea trispora, carotene from the microalgae Dunaliella salina, and astaxanthin from the bacterium Paracoccus carotinifaciens and microalgae Haematococcus pluvialis, respectively. As an example, the production yield of -carotene may be as high as 17g/L of the Blakeslea trispora culture medium.
Based on proprietary research works conducted on carotenoids and azaphilones for 20 years in our laboratory, the talk will emphasize the crucial role that microorganisms and microalgae are currently playing and are likely to continue to play in future as microbial cell factories for the production of food grade pigments and biobased colourants in general. This is due to the versatility in their pigment colour and chemical profile, amenability for easy large-scale cultivation, and a long history of production by well-investigated production strains.
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