For centuries, Monascus purpureus pigments have been used traditionally as a natural food colorant in Asian countries. However, this way is not practical to use in different products due to the production of citrinin by Monascus sp. Co-culture of Monascus purpureus and Saccharomyces cerevisiae is one of the biological ways which significantly reduces citrinin. In this research, the live cells of S. cerevisiae at three concentrations of 103, 104, and 105 cells/mL were used on the 8th, 11th, and 13th days of the M. purpureus fermentation. Analysis of Citrinin and measurement of pigments absorbance were conducted by HPLC and spectrophotometry, respectively. The result indicated that the addition of live cells of S. cerevisiae to Monascus culture improves pigments production and reduces citrinin. Yellow intracellular pigment on day 8 of fermentation at 105 cells/mL yeast cell with the absorbance of 18.40 AU revealed the highest absorbance which was more than three times greater than the control one (5.54 AU). The HPLC results demonstrated that citrinin content at 105 cells/mL live yeast cell on the 13th day of Monascus fermentation (0.9 ppm) was five fold less than its content in the control (4.43 ppm). Above all, results proved that the co-culture of M. purpureus and S.cerevisiae can play an important role to produce not only more portions of pigments but also can warrant more safety.

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