Effects of exogenous ascorbic acid on yields of citrinin and pigments, antioxidant capacities, and fatty acid composition of Monascus ruber

Monascus pigments considered as safe coloring agents had been widely used in food industries until citrinin, a nephrotoxic mycotoxin, was detected in Monascus products. Here, the effects of exogenous ascorbic acid (EAA) both on citrinin and pigments production in submerged cultures of Monascus ruber M2013082 were studied. With the addition of 16 mg/L EAA to the media, the yield of citrinin was reduced by 67.6 ± 0.02% and Monascus pigments was increased by 29.3 ± 0.21% at the culturing time of 132 h. The cultures with EAA showed excellent intracellular antioxidant enzyme activities and extracellular antioxidant activities including free radical scavenging, iron-chelating, and the reducing power, which suggested EAA protected cells from excess free radical damage and then inhibited pigments degradation and citrinin synthesis. Further fatty acid composition analysis showed the increased unsaturated/saturated fatty acid ratio from 1.25 ± 0.02 to 1.40 ± 0.03 and the IUFA value from 77.66 ± 0.32 to 80.67 ± 0.45 facilitated the secretion of intracellular pigments and therefore enhanced pigments production accordingly. Significant increase of fumaric and succinic acids indicated EAA activated Creb cycle resulted in less citrinin precursor of malonyl-CoA formation, which led to the reduction of citrinin synthesis.