Isoelectric point of amino acid: Importance for monascus pigment production

This study aimed to determine the effect of pH on radial growth rate and pigments production from Monascus ruber CCT 3802. Fermentations were carried out in solid medium and submerged fermentations under different pH conditions and the pigments produced were submitted to scanning in spectrophotometer. Higher radial growth rate was obtained when M. ruber   was growing at pH 4.0 and the production of yellow pigment was obtained at low pH (2.0–3.0), while the production of orange and red pigments were in the pH range from 3.0 to 4.0 and above of 5.0, respectively. The results showed that pH has a significant influence on the radial growth rate, pigment production and particularly on the profile of orange and red pigments. pH proved to be an extremely important factor for obtaining orange (precursor) or red pigment, since the isoelectric point of NH3+ sources is critical to converting orange pigment into red pigment.