The pigment characteristics and productivity shifting in high cell density culture of Monascus anka mycelia

Abstract

Background: Monascus mycelia and pigments are promising sources of food and medicine with their potential pharmaceutical values and health-improving functions. Using high cell density fermentation of Monascus spp. to achieve higher mycelium and yellow pigment production is worthy to be researched. In this study, the characteristics and productivity shifting of pigments in high cell density culture of Monascus anka GIM 3.592 were investigated.

Results: The high yield of Monascus mycelia up to 39.77 g/L dry cell weight (DCW), which was achieved by fed-batch fermentation with the feeding medium containing C, N, P and trace elements, was four times higher than that of conventional batch culture. But the total pigment production decreased by 14.6 %, which suggested non-coupled growth. Potential novel yellow pigments accumulated constantly at the late stage of the fed-batch culture, which resulted in a shift in pigment characteristics so that yellow pigments became the dominant pigments. Citrinin production was extremely low and independent of feeding ingredients.

Conclusions: This study provided a suitable fermentation strategy to produce functional Monascus mycelia with a high proportion of yellow pigments in high cell density culture. For the first time, it reported the pigment productivity and characteristics shifting in high cell density culture of Monascus.

Fig. 1

The patterns of residual glucose and DCW with different feeding media in the fed-batch culture. a No.1 medium, (b) No.2 medium, (c) No.3 medium, (d) No.4 medium. Error bars represent the standard deviation of duplicate measurements

Fig. 2

The absorbance of intracellular and extracellular pigments with different feeding media in the fed-batch culture. a No.1 medium, (b) No.2 medium, (c) No.3 medium, (d) No.4 medium. Error bars represent the standard deviation of duplicate measurements

Fig. 3

HPLC determination of citrinin with different feeding media in the fed-batch culture. a Batch culture (control), (b) No.1 medium, (c) No.2 medium, (d) No.3 medium, (e) No.4 medium

Fig. 4

The visual spectra of intracellular pigments with different feeding media in the fed-batch culture. a No.1 medium, (b) No.2 medium, (c) No.3 medium, (d) No.4 medium

Fig. 5

The variation of tone and TLC analysis with different feeding media in the fed-batch culture. a The rate of intracellular yellow pigments to red pigments (Y/R). b The rate of intracellular yellow pigments to orange pigments (Y/O). c TLC atlas in visible light. Lane 1-4: intracellular samples with four different feeding media (from No.1 to No.4) in the 5^th days; Lane 5-8: intracellular samples with four different feeding media (from No.1 to No.4) in the 16^th days; a and b presented the two yellow pigments at R_f values of 0.75 and 0.71, c and d presented the two orange pigments at R_f values of 0.67 and 0.63. d The scanning spectrum of the novel yellow substance