Study On Immobilization Of Monascus Purpureus By NaCS-PDMDAAC Microcapsules

Cultivation of Monascus purpurpeus for production of natural pigments was investigated. A strain of Monascus with high-throughput of pigments in submerged culture named Monascus sp. was obtained through two-step screening strategy, plate selecting and shaking culture determining. The yield of red pigment by Monascus sp. obtained in liquid culture was 1.59 (OD500)The fermentation conditions were optimized to gain the maximum yield of pigments in submerged culture of Monascus sp.. In the first optimization step, the influence of external factors, such as dissolved oxygen and temperature, on pigment production was evaluated and the optimal external conditions were determined. In the second step, the concentrations of initial pH and initial concentrations of glucose, NaNO3 and yeast extract were further optimized to determine the ingredients of the medium. The optimized conditions allowed the pigment production to be increased from 1.59 to 1.93 (OD500) A bubble column, with the diameter and height of 3.5 cm and 25 cm respectively, was made from glass. In comparison with flasks and conventional bioreactor, the bubble column was applied to culture encapsulated Monascus sp. due to its better oxygen transfer property and less stress on microcapsules.Production of pigment in submerged culture was much less than that in solid-state fermentation, since the solid-state culture provided a support for the mycelium. The fermentation of Monascus sp. immobilized in polyelectrolyte complex (PEC) microcapsules, which were prepared by sodium cellulose sulphate and poly-dimethyldiallylammonium chloride, was a good substitute for submerged culture because it mimicked the solid-state environment. The repeated-batch process with encapsulated cells was studied in flasks and a bubble column. It was found that the bubble column was more suitable for encapsulation culture than conventional bioreactor and flasks because of its excellent mass transfer properties and minor breaking stress on microcapsules. Owing to the protection of the microcapsules, the biomass in microcapsules increased to approximately 3 times that in free culture with negligible cell leakage to the medium. And the pigment yield in the bubble column finally reached 3.82 (OD500) which was 2-fold augment, while the period of each batch was shortened to 15% of that in free culture. In the repeated-batch process, the mean productivity of pigment by encapsulated Monascus sp. was 0.158(OD500 h-1), which was nearly 10 times that by free cells. In the kinetic analysis of metabolite production, some changes in pigment production were observed in the repeated-batch process.