Extraction of Bacterial Pigments and Analysing Their Potential as Natural Food Colourants

Pigments isolated from natural sources like bacteria have garnered attention over the last few decades because they are non-carcinogenic, environmentally friendly, and non-toxic as compared to their synthetic counterparts.They have immense potential to be employed for industrial purposes including food and feed industry.The aim of this study was to isolate pigmented bacteria from soil, extract their pigments and to analyze their potential to be used as natural food colorants.Three pigmented bacteria were isolated (green, orange, and yellow).These isolated bacterial cells were characterized using standard biochemical assays like Gram's staining, catalase, oxidase, citrate, MR-VP, urease, indole and starch hydrolysis tests.Following this, the bacterial pigments were extracted using submerged fermentation technique.Different techniques of bacterial cell lysis were tested (like detergent lysis, alkaline lysis and ultrasonication based) and pigments were extracted from these cells after fermentation.The extracted pigments were added to sooji (porridge) and were also tested for their effects on cell-membrane integrity (through LDH leakage assay) and for their biological properties (like trypan blue dye-exclusion, antioxidant and antibacterial assays).The pigments gave good and stable coloration when added to sooji (porridge).The effect of extracted and purified pigments on cell viability of hepatocytes upon exposure to pigments was evaluated by Trypan blue dye exclusion assay and also on cell integrity was assessed by Lactate Dehydrogenase (LDH) assay.Upon exposure to hepatocytes, orange pigment preserved the membrane integrity of hepatocytes and had high percentage of viable cells (93.8%), followed by yellow pigment which had 87.6% of viable cells.The blue pigment (suspected as Pyocyanin) was found to be moderately cytotoxic to cells with decreased cell viability.Dark green pigment was highly cytotoxic and not suitable for use in food items.All the four pigments had good antioxidant activity.The pigments did not show antibacterial effects against Escherichia coli and Staphylococcus aureus.Orange and yellow pigments showed promising results and can be used as food pigments.However, further research on toxicology and organoleptic properties of these pigments is crucial to procure regulatory approval for use in human food.