Microbial Biopigment Production by Rhodotorula sp. Using Horticultural Waste; Its Functionality, Stability and Applications

Potato waste can serve as the growth media component for microorganism’s growth owing to its nutritional profile. The study evaluates different horticultural wastes to utilize it as media component to develop a cheaper media formulation for biopigment production using Rhodotorula sp. MTCC 1446. Proximate analysis of wastes revealed the optimum level of total sugars, reducing sugars, titratable acidity, macro and micronutrients in potato waste for growth of Rhodotorula sp. yeast culture. Concentration optimization showed the 5.0% (w/v) potato waste as media component resulted in 2.82 ± 0.8 g/kg biomass and 259.46 ± 9.5 µg/g biopigment productions. Standardization of growth conditions were carried out implementing Response Surface Methodology. Optimized growth conditions for Rhodotorula sp. were found to be pH 7.0, 30 °C, 66 h incubation time and 362.5 g DAHP addition that lead to production of 34.60 g/L biomass and 3345.82 µg/g biopigment. Validation at 3L scale showed the production of 32.6 g/L biomass and 3152.42 µg/g biopigment with the desirability of 98%. Characterization discovered the presence of carotenoids having antimicrobial, anticancerous, antioxidant properties and stability studies revealed the thermostable (up to 70 °C) and UV light and sunlight stability for 4 h of biopigment. Utilization of biopigment in food products increased the nutraceutical value of the product by increasing its phenolic content as well as appearance of the respected food items. In conclusion, the biopigment produced growing Rhodotorula sp. on potato waste based media under optimal conditions represents a viable natural substitute to artificial food colors in food industry.