Study On The Fermentation Technology Of Theabrownin Produced By Crushed Tea

Theabrownine refers to a high polymer composed mainly of catechins in tea,which is oxidized under enzymatic action.It is a macromolecular brown water-soluble pigment with phenolic properties.It has lipid-lowering weight loss,anti-oxidation,antitumor,and anti-tumor properties,improve immunity and other functions.At present,theabrownine are mainly extracted from Pu’er tea which is fermented in a solid state.The solid state fermentation period is long and the production process is prone to contamination by bacteria,resulting in low production efficiency.Therefore,the rapid and efficient acquisition of theabrownine has gradually become a research hotspot in the utilization of tea plant resources.In this paper,the crushed tea extract is used as raw material to inoculate Aspergillus niger to establish a low-cost microbial liquid fermentation.From the shake flask test to the 100 L fermenter to expand the culture,and the solid-state fermented theabrownine from the chemical composition and antioxidant activity are analyzed.Provide feasible experimental data for the industrialization of liquid fermented theabrownine products.The specific research content is as follows:(1)Optimization of the culture conditions for the shake-flask test of Aspergillus niger liquid fermentation of theabrownine.Preliminarily determine the value of each factor through a single factor test;Subsequently,the material-to-liquid ratio,bacterial liquid concentration and rotational speed were selected as significant influencing factors through the Plackett-Burman test design;Finally,response surface optimization was used to obtain the best culture parameters of liquid fermented theabrownine: The ratio of material to liquid is 1:31(32.26g/L),the concentration of sucrose is 8%(80g/L),the concentration of bacterial solution is about 4.141×106CFU/mL,the speed is187r/min,the fermentation temperature is 28℃,and the content of theafuscin under the conditions of 5d fermentation The theoretical value is 29.341%,after optimizing the conditions,the actual value of the theabrownine content was 29.07%,and the error value from the theoretical prediction value was only 0.93%,which realized the optimization of the culture conditions for the production of the theabrownine on the shake flask.(2)Aspergillus niger liquid fermentation of theabrownine from shake flask test to100 L fermenter expands the culture.On the basis of the best culture conditions in the shake flask experiment,set the oxygen flow rate of the fermenter to 0.5V(V,min),about 168 h of fermentation,the content of theabrownine and the dry weight of mycelium reached the highest,respectively 28.34% and 2.268g/100 mL,which initially realized the expansion of cultivation.(3)Analysis of the chemical composition of theabrownine in the liquid fermentation of Aspergillus niger.Compared with solid-state fermentation,there are significant differences in total sugars,proteins,total phenols and amino acids in theabrownine(P<0.05),and theabrownine produced by liquid fermentation is higher than that produced by solid-state fermentation.Scanning by UV-Vis spectroscopy,both solid and liquid fermented theabrownine reached the highest peak at 250 nm wavelength,indicating that theabrownine were polyphenols.The acidic functional group determination showed that the phenolic hydroxyl group is the main acidic group of theabrownine.(4)Aspergillus niger liquid fermentation of theabrownine antioxidant activity analysis.Solid-state and liquid-fermented theabrownine have the reducing power of potassium ferricyanide,hydroxyl radical scavenging rate,superoxide anion free radical scavenging rate and DPPH free radical scavenging rate,respectively,all are compared with Vc.The order of antioxidant capacity is Vc>liquid-fermented theabrownine >solid-state fermented theabrownine.