ABSTRACT
Stimulation of carotenogenesis in carotenoid producing red yeasts, algae, or bacteria for enhanced carotenoid production has been achieved by mevalonic acid addition. Recently, carotenoid-enriched feed was produced by Phaffia rhodozyma fermentation of inexpensive animal feeds. Because mevalonate improves carotenoid yield in P. rhodozyma in synthetic medium, this study tested whether a similar enhancement was possible in biobased substrates. Four concentrations, 0, 0.02, 0.04, and 0.1% of mevalonate as a precursor of P. rhodozyma production of astaxanthin and β-carotene were evaluated in five substrates: defatted rice bran, full fat rice bran, wheat bran, corn whole stillage, and synthetic media. Additionally, four concentrations, 0, 0.05, 0.1, and 0.5% of apple pomace and tomato pomace were also evaluated as precursors of carotenogenesis in P. rhodozyma fermentation of corn whole stillage and rice bran. Mevalonic acid, tomato pomace, and apple pomace enhanced carotenoid yields in all substrates in that order. However, the optimal concentration of precursor and the percent increase of carotenoid yield in each substrate were variable, potentially indicating substrate influence on carotenoid stimulation. Among animal feed substrates, mevalonic acid in corn whole stillage resulted in the best astaxanthin yield of 220 μg/g and β-carotene of 904 μg/g. Tomato pomace resulted in 29% astaxanthin and β-carotene enhancement in corn whole stillage, and apple pomace increased β-carotene production by 26% in whole stillage. The use of expensive mevalonate is offset by the inexpensive process of producing carotenoid-enriched DDGS. Optimization of tomato or apple pomace addition may further enhance the carotenoid yields.
