Effect Of Gastrodin On The Production Of Citrinin By Monascus Fermentation And Its Product Preparation

Monascus,a filamentous fungus used for both medicine and food,can produce a large number of metabolites beneficial to human body,such as pigments,Monacolin K and so on.However,at the same time,it is often accompanied by the production of mycotoxin-citrinin,which restricts the application of red yeast products.Therefore,how to effectively reduce the production of citrinin without reducing or even increasing the pigment yield in Monascus fermentation process has become one of the research hotspots.Gastrodin,a small molecule phenolic glycoside compound,is the main active substance of traditional Chinese medicine Gastrodia elata,which has anti-inflammatory and antioxidant effects.It has not been reported whether gastrodin can affect pigments and citrinin in solid and liquid fermentation of Monascus.Therefore,in this paper,rice was used as the main fermentation substrate,and gastrodin was added in the solid and liquid fermentation processes of Monascus to study its influence on the production of pigments and citrinin in fermentation.The possible mechanism of gastrodin was analyzed by transcriptomics in liquid fermentation,providing an important reference for further exploration in the effect of gastrodin on citrinin.The main research content is as follows:(1)Monascus AS3.4384 and Monascus purpureus 30141 were used as the research object.Rice was used as the solid-state fermentation substrates.Solid state fermentation conditions are optimized.The effects of gastrodin on pigment yield and citrinin yield were also studied.The results showed that for AS3.4384,when the rice weight was 15 g/250 m L conical bottle and the dosage of gastrodin was 0.04 g,after7 days of fermentation,the yield of citrinin decreased by 60.08% without reducing the pigments yield.For Monascus purpureus 30141,the weight of rice was 30 g/250 m L conical bottle and the dosage of gastrodin was 0.02 g.After 7 days of fermentation,the yield of citrinin decreased by 70.03%.Based on the optimized fermentation conditions of AS3.4384 strains,the reducing effect of 0.04 g gastrodin on citrinin in indica rice and pearl rice was investigated,and the yield of citrinin decreased by 50.18% and 61.27%,respectively.The residual amount of gastrodin in japonica rice after fermentation was determined by HPLC,and it was found that the residual amount was small.No gastrodin was detected in fermented pearl rice and indica rice.These results indicate that gastrodin can be used as a good exogenous additive in solid fermentation.(2)Monascus AS3.4384 was used as the research object.We optimized the liquid fermentation conditions by optimizing carbon source types,japonica rice powder adding quantity,number of days of fermentation,gastrodin addition to explore the effect of gastrodin for citrinin and pigments yield in liquid fermentation.The results showed that gastrodin had the best effect on citrinin without affecting the pigment yield when the substrate was japonica rice.After optimization,japonica rice flour substrate mass was 20 g/L,gastrodin addition was 10mg/100 m L,and after fermentation for 10 days,it was found that it had the best reduction effect on citrinin,which could reach 56.77%,without affecting the pigment yield.(3)A preliminary investigation of the effect of gastrodin on the reduction of citrinin production in liquid fermentation of Monascus AS3.4384 was carried out by transcriptomics.The data from the different groups were analysed with reference to the gene sequences of Monascus AS3.4384 previously sequenced in our laboratory,and the correlation coefficients were found to be above 0.9 in both groups,providing assurance of the reliability of the data.A total of 128 differentially expressed genes were identified,of which 90 were significantly up-regulated and 38 were significantly down-regulated.No gene involved in citrinin biosynthesis was found in these differentially expressed genes after control analysis.The enrichment analysis showed that the above differentially expressed genes were concentrated in the pathways related to gluconeogenesis in Monascus which has an important physiological metabolic role in Monascus,and it is hypothesized that asparagine may affect the biosynthesis of its secondary metabolites by influencing some of these processes during gluconeogenesis in Monascus.(4)Based on the effect of gastrodin on citrinin reduction in solid-state fermentation in Chapter 2,the red yeast rice flour with low yield of citrinin and high pigment was designed and produced,and its physical and chemical indexes,sensory evaluation and microbial content were determined to provide reference for the combination of gastrodin and red yeast solid-state fermentation and provide a new idea for the development of red yeast rice flour.