Development Of A Gastrointestinal Simulation Reactor And Its Preliminary Application

Gastrointestinal reactor has great application value in the research of human digestive tract,intestinal microbes and probiotics.In addition to the characteristics and functions of ordinary bioreactor,gastrointestinal reactors also need to simulate the physiological environment and dynamic characteristics of the gastrointestinal tract.Dynamic digestion model reactor simulating the stomach and small intestine and dynamic fermentation model reactor simulating the large intestine are two kinds of gastrointestinal reactors with complex structure,perfect function and good simulation results.In recent years,several domestic and foreign scientific research teams have developed their dynamic digestion and fermentation model reactors,and some of the reactors have been widely used in the research of intestinal microbes and probiotics.However,the existing dynamic digestion model reactor and dynamic fermentation model reactor have different structures and are not universal.Combining the separated reactors would increase the complexity and the cost of experiments.In this study,the dominant features of the two kinds of reactor were integrated,and a gastrointestinal simulation reactor?GSR?with programmable logic controller?PLC?was developed.The effect of GSR in simulating the digestive function of the stomach and small intestine was verified,and GSR was also preliminarily applied to the fermentation of Lactobacillus acidophilus.Firstly,the structure of reaction chambers was optimized designed by structure comparison and mathematical calculation.Through exhaust gas discharge and collection device,the collection time of 10 mL air in GSR was 15 min and the volume recovery rate were85.7%.The collection time of 50 mL air was 7 min and the volume recovery rate were 96.4%.This device could prevent outside air from entering the reactor,which helped maintain the anaerobic condition.Currently,no device with the same function has been reported in the gastrointestinal reactors.GSR was operated automatically through a control system based on PLC.Secondly,the performances of GSR during simulating peristalsis,emptying and mixing were tested through cold model experiments.In order to increase the similarity between pressure curves in GSR and in vivo,the parameters of GSR simulating peristalsis was optimized.It showed that the contraction frequency and pressure curves were accord to the data in vivo.The contraction frequencies of GSR simulating the peristalsis of stomach,small intestine,and colon were 3 times·min^-1,10-11 times·min^-1,and 12 times·h^-1,respectively.The structure of GSR and its control parameters were optimized by analyzing the results of curve fitting between the emptying curves in GSR and the Elashoff's model describing the gastrointestinal emptying.The results of curve fitting were significantly better after optimization.The results of mixing in GSR was analyzed.It showed that the mixing process of inulin solution in GSR was accord to the theoretical pattern of complete mixing flow,and it was also accord to the mixing of low-viscosity nonnutrient meal in human stomach.Thirdly,the reliability of GSR as an in vitro fermentation device was verified through the process of automatic adjustment of pH value and sterility experiment.PID algorithm was adopted to realize the automatic adjustment of the pH value in GSR.Within the range of pH4⁷,the maximum relative error between online and offline pH value was 2.88%.It took 100min to adjust and stabilize pH value from 4.6 to 5.7 automatically.The sterility of GSR was verified.Lastly,GSR was applied to the fermentation of Lactobacillus acidophilus.The viable biomass was maintained at about 3×107 cfu·mL^-1 in 6.5 days,which showed that GSR had the advantage of maintaining the viability of Lactobacillus acidophilus for a long time.Online pH value was used as an index to determine the growth status of Lactobacillus acidophilus,which was testified to be reliable.The circulation function of diluent could prevent viable biomass from reducing effectively,which means this function played an important role in maintaining the viability of Lactobacillus acidophilus.It was preliminarily demonstrated that GSR had the potential in the application in in vitro fermentation of intestinal micldrobes.