Cultivation of Monascus purpureus (CCRC 31615) for the production of natural pigments was investigated. Traditionally, Monascus species were grown on rice by solid-state culture. For large-scale cultivation, solid-state cultures were associated with some problems such as contamination and scale-up. By using submerged cultures with rice particles, a stirred-tank fermentor was not suitable for submerged cultures as the impeller tended to break the particles into small pieces. A conventional bubble column was also unsuitable as its mixing capability was poor. In the present study, a modified bubble column with wire-mesh draft tubes was employed for the cultivation of M. purpureus. The proposed column had a shorter mixing time and a higher oxygen transfer rate relative to the conventional bubble column. The production of pigments using the proposed column was up to 80% higher than that achieved using the conventional bubble column.

A process taking advantages of combined solid-state and submerged cultivation of Monascus for red pigment production and integration of a product removal unit was developed. The solid-state cultivation was carried out in a 5 l fermentor, with rice being used not only as the substrate but also the support for Monascus. The inclusion of rice submergence and integration of product separation were achieved by intermittently rinsing the rice with monosodium glutamate (MSG) solutions every 12 h followed by an adsorptive extraction of the red pigment dissolved in the rinsing solution. With this new process, the Monascus red pigment production was increased by 24% as compared with that by the plain fixed-bed cultivation.