Production Of Natural Food Pigments From Chinese Rice Wine Wastes In Submerged Fermentation By Monascus

Monascus pigments（MPs）are natural pigments metabolized by Monascus and have functional properties such as anti-cancer,anti-oxidation and anti-obesity.The brewing process of Chinese rice wine will generate a large amount of waste.At present,its comprehensive utilization level is very low,and low-value utilization is common.The random discharge of Chinese rice wine wastes has caused waste of resources and seriously affected the safety of the ecological environment.The purpose of this study is to explore the process of using Chinese rice wine waste to produce MPs,so as to realize the high-value utilization of Chinese rice wine wastes.In this study,Monascus purpureu ZK-2 was used as the starting strain.Under the condition of submerged fermentation in shake flask,the effects of the ratio of solid to liquid and the amount of broken rice on the yield of MPs were discussed,and the effect of stirring speed on the yield of MPs was discussed in pilot scale fermentation.In addition,the bioconversion of organic matter during fermentation and the physicochemical properties of MPs were also discussed.This work provides a green way for the high-value utilization of agricultural waste and helps to realize the industrialized production of MPs.The main findings are as follows:（1）The main nutritional components of Chinese rice wine wastes were analyzed and the process of producing MPs by submerged fermentation in shake flasks was explored.The main components of Chinese rice wine lees were crude protein（46.7±1.8%）,crude starch（10.5±0.2%）and crude fat（11.3±0.4%）,also included a small amount of crude fiber and residual reducing sugar,aflatoxin B₁was not detected.The contents of total solids and total suspended solids in rice soaking water were 72.1±5.6 g·L^-1 and 15.3±2.1 g·L^-1,respectively,including reducing sugars,soluble proteins,organic acids and a small amount of NH₄⁺-N.Rice soaking water contains more organic substances,the soluble chemical oxygen demand（SCOD）is 64.3±4.6 g·L^-1.By exploring the submerged fermentation process in shake flasks,first of all,it is determined that the optimal solid-liquid ratio is 1:10,the highest concentration of MPs was38.52 U·m L^-1,and biomass was 6.37 g·L^-1.Then,the effect of the addition amount of broken rice on the production of MPs was further explored.Based on the solid-liquid ratio of 1:10,when the initial addition amount of broken rice was 30 g·L^-1,the concentration of MPs reached the highest 120.1 U·m L^-1,and biomass was 12.6 g·L^-1.（2）In the pilot scale experiment,the effect of stirring speed on the yield of MPs was explored.It was found that the mycelium ball with small diameter and large specific surface area was a better form of MPs production.Through the analysis of fermentation kinetics,at 400rpm,the yield of MPs reached the maximum value,which was 8174 U·g^-1;the MPs concentration was 128.4 U·m L^-1;the specific product yield was the highest,which was 421.32U·g^-1·h^-1.At a stirring speed of 600 rpm,the specific growth rate was the largest at 0.362 h^-1.Using the two-stage stirring speed control strategy in a 50 L stirring fermenter,the maximum specific growth rate and specific product yield of MPs were 0.518 h^-1 and 567.00 U·g^-1·h^-1,respectively,which were increased by 43.1%and 34.6%;the fermentation time of MPs was advanced by 12 h;the maximum MPs concentration was 158.9 U·m L^-1,an increase of 23.8%;the highest MPs yield was 9914 U·g^-1,an increase of 23.3%.When studying the bioconversion of organic matter in the fermentation broth,Monascus ZK-2 can’t utilize NH₄⁺-N.In prophase of fermentation,the hydrolysis rate of carbohydrates by Monascus is greater than the consumption rate,result in a decrease of reducing sugar concentration,then the hydrolysis rate is less than the consumption rate,causes a rapid reducing sugar drop.The trend of soluble protein concentration increased first and then decreased,which was caused by its own metabolic decomposition and intracellular protein secretion.The SCOD removal rate of Monascus ZK-2to the fermentation broth was 78.7%,and it had a certain ability to treat fermentation wastewater.（3）The MPs fermentation broth was treated by spray drying,and the physicochemical properties of the MPs powder were determined.The valuecontents of total arsenic,heavy metals and citrinin in MPs powder were 0.13 mg·kg^-1,0.0532 mg·kg^-1 and 0.27 mg·kg^-1,respectively,which were far lower than the national standard.Aflatoxin B₁and GABA were not detected in MPs powder,and the content of color value was 1934.0 U·g^-1.The results of FT-IR analysis showed that MPs powder contained more red pigments and more characteristic bands of carbohydrates,which proved that MPs had typical structural characteristics of polysaccharides.The results of SEM analysis showed that under low magnification,the spray-prepared MPs powder had a round granular appearance,and the surface roughness was not strong,and it was not easy to form agglomerates,wrinkling,possibly caused by rapid evaporation of water during spray drying or the absence of pigment carriers and protectants.DSC analysis results show that the melting temperature of red yeast rice powder is 93.5℃,which is mainly related to the endothermic evaporation of water and the breaking of hydrogen bonds,and there is an exothermic peak at 281.4℃in the curve,which may be MPs powder caused by thermal degradation of polysaccharide in flour.