Preparation of Extracellular and Intracellular Water-Insoluble Monascus Pigments during Submerged Fermentaion

Abstract

Monascus pigments (MPs) are a group of secondary metabolites produced by the filamentous fungus Monascus. In this study, the dominant MPs in the submerged cultures of Monascus ruber M7, rubropunctatin and monascorubrin, were found to be produced both intracellularly in the cell-bound state and extracellularly in the form of free crystals. To prepare and quantify the extracellular and intracellular water-insoluble MPs (wiMPs), separation of the extracellular crystalline MPs (ecMPs) and mycelia from the fermentation broth was carried out by filtration using filter papers (FPs), nylon mesh filters (NMFs), and sand core funnels (SCFs). Subsequently, the collected ecMPs and mycelia were subjected to microscopic observation and MPs quantitative analysis to evaluate the separation efficiency. Results showed that 200 to 300 mesh/inch NMFs were the optimum filters for separating the ecMPs and the mycelia. This study is the first comparative analysis of different filters for the preparation of extracellular and intracellular wiMPs. It would lead further investigations on the production and secretion of wiMPs by Monascus.