Abstract—Colorants produced by various Monascus sp. are well established in Asiatic foods. Industrial production of Monascus pigments involves expensive submerged culture fermentation. A less expensive alternative is the use of solid state fermentation. This study reports on color production by Monascus ruber ICMP 15220 in packed bed solid state culture. The fungus was grown in packed beds (0.05 m in diameter and 0.17 m in depth of substrate) of moistened rice. The bed of rice was continuously aerated by sparging with humidified air (95–97% relative humidity). The effects of different aeration rates (0.05-2.0 L min-1) and initial moisture level (45, 57.5, 70% (w/w)) in the substrate, on color production are reported. The packed bed solid state fermentations were carried out at a nominal temperature of 30oC. A forced aeration rate of higher than 0.5 L min-1 reduced the production of the pigments and biomass as a consequence of water loss from the bed. Highest levels of pigments were obtained at forced aeration rates of between 0.05 and 0.2 L min-1. Under these conditions, the pigment content reached ≥ 98 AU per g dry matter in the bed. An initial moisture level of 45% (i.e. g water per 100 g wet substrate) resulted in very low production of pigments and biomass with final moisture content of 29.6%. An initial moisture level of 70% gave the highest pigment production in the fermented dry solids and also the highest pigment productivity, which were 1,415 AU per g dry matter and 101 AU per g dry matter per day, respectively. The results suggest that forced aeration rate and initial moisture level in the substrate have a strong influence on pigment production in solid sate fermentation of M. ruber.

Index Terms—Aeration rate, food colorants, Monascus ruber, solid state fermentation.

Farhan M. Said is with the School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand, on study leave from University Malaysia Pahang, Malaysia (e-mail: farhan_msaid@yahoo.co.uk).
Yusuf Chisti is a Professor with the School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand (Tel:+64-6-350 5934; fax: +64-6-350-5604; e-mail: Y.Chisti@massey.ac.nz.).
John Brooks is a Professor with the Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, New Zealand(e-mail: john.brooks@aut.ac.nz).

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Cite: Farhan M. Said, Yusuf Chisti and John Brooks, "The effects of forced aeration and initial moisture level on red pigment and biomass production by Monascus ruber in packed bed solid state fermentation," International Journal of Environmental Science and Development vol. 1, no. 1, pp. 1-4, 2010.