Statistical optimization of process variables for anti-hypercholesterolemic metabolites production from Monascus purpureus MTCC 369 fermented finger millet

Abstract

Monascus purpureus fermented rice has been used for centuries to treat hypercholesterolemia, indigestion, and diarrhea in East Asian countries. Monacolin K, also known as lovastatin, a secondary metabolite synthesized by Monascus sp. in fermentation, is mainly responsible for reducing the level of blood lipids. Besides statins, sterols produced in this process have also been reported to have hypolipidemic effects. In the current study, statin and total sterol production by M. purpureus microbial type culture collection and Gene Bank MTCC 369 on finger millet (FM) substrate were investigated. The central composite design of the response surface methodology (RSM) was used for the optimization of different fermentation process independent variables such as fermentation time period, temperature, inoculum volume, and pH for maximum production of statins and total sterols by M. purpureus MTCC 369. The maximum statin (9.78 mg/g) and sterol (0.46 mg/g) production was achieved at a temperature of 29.44°C, pH 5.0, inoculum size 5.37 ml, and fermentation time of 13.8 days. Fermentation process factors such as fermentation time period and temperature were significant positive factors, while pH and inoculum volume were found to be insignificant factors. The interactive effects of the positively influencing variables have been demonstrated. Compared with the traditional production of these metabolites, using FM as a substrate is promising for the high production of anti-hypercholesterolemic metabolites. The current study was aimed at optimization of the solid-state fermentation process of statin and total sterol using RSM for nutritional FM so as to improve M. purpureus-fermented FM (like red yeast rice) with health-promoting properties. This is the first report on the optimization of statin and sterols from M. purpureus MTCC 369 fermented FM with a significant yield that is on par with that reported so far.