Improvement of red pigment production and citrinin reduction from Monascus purpureus using dairy sludge: potential health benefits and fermentation strategies

Abstract

This study aimed to explore the production of red pigment from Monascus purpureus and its potential health benefits. The research started with the cultivation of M. purpureus in an environment containing dairy sludge. Subsequently, the extracted pigment was purified and subjected to various analyses, including liquid chromatography mass spectrometry (LCMS) and nuclear magnetic resonance (NMR) to verify its purity, high-pressure liquid chromatography (HPLC) to measure the citrinin levels, microbial testing, and assessment of antioxidant activity. Finally, fermentation was conducted in a batch system using a fermenter. M. purpureus was grown in a medium composed of dairy sludge, monosodium glutamate, and glucose, resulting in a biomass yield of 26.15 g/l. After extraction and purification, the optimal sample yielded 4.85 g of dry color, while the control sample produced 2.5 g. Analysis using NMR revealed similarities between the samples, while HPLC indicated low citrinin levels of less than 0.05 ppm in the optimal sample and 2.5 ppm in the control sample. LCMS analysis demonstrated a purity of 91.9% for the optimal sample, which also exhibited antimicrobial and antioxidant activity. In the fermenter, the sample obtained from optimal culture conditions displayed the highest concentration of the pigment monascorubramine, maximum specific growth rate of 0.029/1/h (µmax), a cell yield (Yx/s) of 0.29 g/g, and a production efficiency of 65% for M. purpureus. Overall, the produced pigment sample exhibited potential for use in the food industry due to its low citrinin content and high concentration of red pigment.