Red bacterial cellulose production by fermentation of Monascus purpureus

Red and yellow pigments are secondary metabolic products secreted by Monascus purpureus strains on bacterial cellulose Acetobacter xylinum TISTR 975. In this paper, we study pigments secreted by the strains M. purpureus TISTR 3002, M. purpureus TISTR 3180 and M. purpureus TISTR 3385 grown in Modified Yeast Malt Extract. The experiment was carried out on a rotating shaker at 250 rpm under 30°C for 14 days. The results showed that the rate of red pigment production by 3385, 3002 and 3180 are 0.093, 0.036 and 0.029 UA, respectively. TISTR 3385 revealed the highest pigment production with a ratio of 1.18 times 3002 and 1.68 times 3180. The substrate consumption decreased with increasing fermentation time. The results also showed that 3385 substrate consumption of 0.168 g/L/day was 1.22 times higher than that of 3180 (0.138 g/L/day) and 1.85 times higher than 3002 (0.091 g/L/day). Total color differences were also evaluated and showed that 3002 exhibited a 2.25 times higher color yield (1.51 unit/day) than 3385 (0.67 unit/day) and 3.78 times higher than 3180 (0.40 unit/day). Results revealed that this red bacterial cellulose contained 3.41 g/L carbohydrate, 0.054 g/L protein, 20% (w/v) lipid, 95% (w/w) moisture content with mineral values of calcium, iron and phosphorous of 10, 4 and 1 mg/100g, respectively. Monacolin K and citrinin were not found in fermented bacterial celluloses. The pigmented color derived from Monascus bacterial cellulose can therefore be used as a safe food source that is not contaminated by citrinin.