Production and optimization of carotenoid-enriched dried distiller's grains with solubles by Phaffia rhodozyma and Sporobolomyces roseus fermentation of whole stillage.

Whole stillage--a co-product of grain-based ethanol--is used as an animal feed in the form of dried distiller's grain with solubles (DDGS). Since animals cannot synthesize carotenoids and animal feed is generally poor in carotenoids, about 30-120 ppm of total carotenoids are added to animal feed to improve animal health, enhance meat color and quality, and increase vitamin A levels in milk and meat. The main objective of this study was to produce carotenoid (astaxanthin and β-carotene)-enriched DDGS by submerged fermentation of whole stillage. Mono- and mixed cultures of red yeasts, Phaffia rhodozyma (ATCC 24202) and Sporobolomyces roseus (ATCC 28988), were used to produce astaxanthin and β-carotene. Media optimization was carried out in shake flasks using response surface methodology (RSM). Macro ingredients, namely whole stillage, corn steep liquor and glycerol, were fitted to a second-degree polynomial in RSM. Under optimized conditions, astaxanthin and β-carotene yields in mixed culture and P. rhodozyma monoculture were 5 and 278, 97, and 275 μg/g, respectively, while S. roseus produced 278 μg/g of β-carotene. Since the carotenoid yields are almost twice the quantity used in animal feed, the carotenoid-enriched DDGS has potential application as "value-added animal feed or feed blends."