Due to consumer demand, food manufacturers worldwide are moving to produce more natural colours, in an effort to replace potentially harmful artificial colourings now used in many foods and beverages.
Food colouring now represents a $1.2 billion global market, with natural colours capturing 31% of the food market, but growing at a rate of 5%. However, these natural colours are largely plant extracts that have the disadvantage of variability and seasonal supply. Microbial cell production, in contrast, offers a reliable and scalable pigment production technology.
The aim of this research project has been the screening of pigment-producing microbes from New Zealand environment to select those presenting potential for production of food-grade colorants. Our selection has been based on the microorganisms (e.g. bacteria, fungi and microalgae) producing pigment molecules that fit current market demands for specific colour shades and pigment chemical properties.
The iconic deep sky-blue pink gill mushroom of New Zealand, Entoloma hochstetteri, and its crude pigment extract in methanol.
We have so far screened 286 pigment-producing microbial strains isolated in New Zealand. Among those, we have tested the stability to light, temperature and pH of 121 pigment extracts. A total of 43 microbial strains have been short-listed based on the chemical properties and colour-shades of their pigments. Molecular identification of the selected strains using ribosomal DNA sequencing showed the presence of 12 undetermined genera and 31 known genera including 37 bacteria, 5 fungi and 1 microalga.
Bacterial strain SVB-B15 isolated from New Zealand stream water produces a water-soluble orange pigment mostly formed by hydrophilic carotenoids.
Colour shades in methanol solutions of the pigments extracted from short-listed microbial strains and their respective water solubility.