A kind of potential food additive produced by Streptomyces coelicolor: Characteristics of blue pigment and identification of a novel compound, λ-actinorhodin

The blue pigment produced by Streptomyces coelicolor 100 with a yield as high as 3 g/l is a mixture of 10 components. The structure of one of the components was identified and it is a new actinorhodin analogue, named as λ-actinorhodin. The natural pigment can be dissolved in alkaline water solution and a number of organic solvents in common use. The color of a water solution of the pigment changes with pH value. The pigment is stable to light, heat and food additives in common use, and resistant to oxidants and reducers under acidic conditions and to reducers under alkaline conditions. Most inspected metal ions hardly affected pigment stability except for Fe2+ at high concentration and Pb2+. The pigment is nontoxic with LD50 > 15,000 mg/kg in an acute toxicity trial. The good characteristics of the pigment make it potential useful in the food processing industry as an additive.