Production Of Monacolin K By Solid-state Fermentation Of Monascus Ruber 9901 Using Pomelo By-products

With the development of economy,the improvement of national living standard and the change of life style,the number of people suffering from hyperlipidemia,hypertension and other cardiovascular diseases has increased sharply.Monacolin K,the main component of functional Monascus,has significant lipid-lowering effects and is increasingly favored by the health industry with broad development prospects.In previous reports,grain is often used as the fermentation substrate for Monacolin K production by Monascus,with higher cost.How to reduce the cost and increase the yield of Monacolin K by broadening the sources of raw materials for the production of functional Monascus is the research trend of solid-state fermentation of Monacolin K.So it is worth exploring how to control cost reasonably,broaden the source of raw materials for the production of functional Monascus,and improve its yield.The comprehensive utilization of food processing by-products can avoid the waste of resources,improve the economic utilization rate of products,and reduce environmental pollution.Microorganisms use food by-products for solid state fermentation to produce various active substances,which have been studied and applied for many years However,the production of Monacolin K by solid state fermentation of food processing byproducts by Monascus is less studied and the yield is generally low,so there is still a large space for research and development.Thus,a further research is inevitable.In this study,the yield of Monacolin K was increased by selecting the food by-product fermentation substrate and optimizing the process conditions.Meanwhile,the change of substrate during solid-state fermentation was analyzed to preliminarily explore the reason why pomelo by-products promoted the synthesis of Monacolin K.In this experiment,Monascus ruber 9901,a strain with high yield of Monacolin K,was used as the experimental bacteria to optimize the initial water content,inoculation amount,carbon source type,nitrogen source type,lactose addition amount,and fermentation time was designed.Based on among results,the response surface was optimized by Design-Expert method for the inoculation amount,lactose addition amount,initial water content.The results showed that the optimal conditions for the production of Monacolin K were 46.4%initial water content,8.5%inoculation amount,3.4%lactose content,and incubated at 30℃for 2 d followed with 25℃until 22 d.Under the optimal conditions,the maximal yield of Monacolin K is 6984.9 mg·kg^-1.In the second stage,the biotransformation effect of Monascus 9901 was further investigated.The morphology,chemical composition and antimicrobial of pomelo by-products before and after fermentation were analyzed.After fermentation,the morphology of pomelo by-products become greatly than initial stage,and the gap structure of pomelo by-products was basically retained.In contrast,the specific surface area of pomelo by-products after fermentation increased,and the more material consumption in the matrix was obvious.After dynamic monitoring of fermentation process,it was found that Monascus could effectively use the nutrients in the pomelo by-products.The dry weight,pectin,total sugar,protein and total polyphenols were decreased by 32.1%,69.1%,89.2%,89.3%and 12.1%respectively after fermentation.Similarly,the content of total flavonoids and naringin increased by 525.5%and 100%,respectively.The antibacterial effect of the fermented product was evaluated preliminarily.The antimicrobial of pomelo by-products after fermentation was detected.The antimicrobial of pomelo by-products was 18.1 mm against Bacillus subtilis and 14.5mm against Staphylococcus aureus,but it had no antimicrobial against Escherichia coli.To explore whether pomelo by-products extract could promote the production of Monacolin K from other low-yielding food by-products using Monascus ruber 9901.In this experiment,the water and alcohol extracts of pomelo by-products were added to the fermentation substrate of Lentinus edodes stem and orange cores for solid state fermentation.The results showed that both the water and alcohol extracts of pomelo by-products could enhance the production of Monacolin K.This paper can open up a new utilization way for the high-value utilization of pomelo by-products,and provide a beneficial reference for promoting the development of functional Monascus industry.It has important research significance and practical application potential.