Abstract: This study aimed to optimize the solid-state fermentation process of a mixture of highland barley bran and coix seed (1:1, m/m) by Monascus purpureus (CICC.5046) for improved production of Monacolin K as a hypolipidemic agent by the combined use of one-factor-at-a-time method and response surface methodology. The changes in the main substances with physiological activities were investigated during the fermentation process. The one-factor-at-a-time experiments selected fermentation temperature, inoculum size and filling quantity as the main factors that affect the production of Monacolin K, and these factors were optimized by response surface methodology to be 29 ℃, 8% and 40 g of substrates with 60% water added contained in a 250 mL beaker, respectively. After fermentation for 12 d under these conditions, the Monacolin K yield was 110.556 mg/kg. During the fermentation, Monacolin K, pigments and soluble polyphenols were significantly increased whereas soluble polysaccharides, total flavonoids and β-glucan were decreased significantly. In general, the substance with hypolipidemic activity was increased more significantly.

Key words: highland barley bran, coix seed, Monascus purpureus, Monacolin K, response surface methodology