LAUSR

BACKGROUND Monacolin K, an important secondary metabolite of Monascus, possesses a cholesterol-lowering effect, and is widely used in the manufacture of antihypertensive drugs. In this study, we constructed an extractive fermentation system by adding nonionic surfactant and acquired a high Monacolin K yield. The mechanism was determined by examining both cell morphology and the transcription levels of the related mokA-I genes in the Monacolin K biosynthetic gene cluster. RESULTS Monacolin K yield was effectively increased to 539.59 mg L-1 during extraction, which was an increase of 386.16% compared to that in the control group fermentation. The nonionic surfactant showed good biocompatibility with Monascus. Electron scanning microscopy revealed alterations in the morphology of Monascus. The loosened mycelial structure and increased number of cell-surface wrinkles were found to be related to the increased cell-membrane permeability and extracellular accumulation of Monacolin K. Gene expression levels were measured via RT-qPCR. In contrast with control group, mokA, mokB, mokC, mokD and mokF showed higher-level and longer-term expression in the extractive fermentation group, while mokE and mokG did not present the similar trend. The expression levels of mokH and mokI, encoding a transcription factor and efflux pump, respectively, were also higher than the control levels. CONCLUSION Addition of a nonionic surfactant to Monascus fermentation effectively increases the yield of Monacolin K by transforming the fungus morphology and promoting the expression of Monacolin K biosynthesis genes. This article is protected by copyright. All rights reserved.