Investigation of relationship between lipid and Monascus pigment accumulation by extractive fermentation

Abstract

Fermented Monascus pigments have been utilized as traditional Chinese medicine and food colorant for thousands of years. Under the limited nitrogen concentration and/or low initial pH 2.5 conditions, it was observed that production of intracellular pigments and accumulation of microbial lipids (high content reaching to approximately 50% in dry cell weight) by edible Monascus anka exhibited a positive correlated relationship. Extractive fermentation in nonionic surfactant micelle aqueous solution selectively exported the intracellular Monascus pigments into its extracellular broth, in which the concentration of intracellular pigments was negligible while the extracellular one was enhanced. The extractive fermentation provides a novel strategy for shifting of the metabolic channeling from intracellular lipid accumulation to Monascus pigment production. High pigment concentration, i.e., approximately 40 AU of extracellular Monascus pigments, was achieved by extractive fermentation at a relatively high nonionic surfactant concentration 10g/l. This phenomenon might be attributed to the nonionic surfactant micelles acting as pigment reservoirs by biomimetic of intracellular lipids.