Study Of Submerged Fermentation And Growth Kinetics Of Morchella

Morchella are well known as a kind of rare edible and officinal fungi all overthe world. Scientific research indicates that Morchella possess high nutritionalvalue and multi-officinal function. At present, Morchella are badly lacking so theprice is high all the time. Artificial planting of fruit body of Morchella can not beeffectively repeated and verified, therefore industrialization production ofMorchella has not succeeded yet. In this paper, we mainly study on cultivatingmycelium of Morchella by the method of submerged fermentation, in order tosearch a new way of exploiting Morchella. By optimizing the parameters, we canobtain the maximum yield 16.28g/L, which can be a foundation forindustrialization production. At the same time we establish the model of growthkinetics of Morchella, which is prepared for forecasting and optimizing control.Our main research work and conclusions are as following:1. Research on the difference between fruit body and mycelium. Contrast onthe main chemical component of fruit body and the mycelium, the results showthat they do not have much difference in ash, total saccharides, protein, Vitamin B1and Vitamin B2, which is consistent with the conclusion in other literatures. Theconclusion proves the feasibility of cultivating mycelium instead of planting fruitbody of Morchella.2. Optimizing the components of medium. By the method of shake-flaskfermentation, carrying on single-factor test about carbolic medium, nitric medium,and growth gene, choose corn flour, soybean flour and wheat bran as nutritionmedium. Then carrying on the Orthogonal experiment about the concentration ofcorn flour, soybean flour, wheat bran and MgSO4 ,KH2PO4, we find the optimummedium is that: wheat bran 4%, corn flour 2%, soybean flour 1%, MgSO40.1%,KH2PO4 0.1%.3. Optimizing the conditions of shake-flask fermentation. Carrying on theOrthogonal experiment about the factors of temperature, frequency of shake-flask,load capacity and fermentation cycle, we found the sequence of factors influencingthe yield is fermentation cycle> temperature> frequency of shake-flask> loadcapacity, and the optimum fermentation conditions are 28 ℃ , 120 rpm ,50ml /250ml , fermentation for 5 days. We research on the influence for yield ofdifferent initialized pH. The results indicate that the optimum initialized pH rangeis 5.5-6, and the nature pH of the culture medium is 5.8, which is in the optimumrange. CMC is being used to adjust the viscidity of medium, in order to analyzethe effect for yield of different viscidity. We found that the yield decrease as thefermentation viscidity increasing, so we need not add CMC to the fermentationliquid. Under the optimum condition, we can obtain the maximum yield 5.7 g Lofshake-flask fermentation .4. Optimizing parameters of liquid seed cultivating. Through experiment, wechoose the optimum culture medium for liquid seed is potato 10%, sucrose 3%,peptone 0.1%, zymoid grease 0.5%, KH2PO40.05%,MgSO40.05%. The optimumfrequency of shake-flask is 100rpm and the optimum inoculating quantity is 1/2cuvette. At the same time we established a new way of using image analysemethod to plot growth curve. The relative error between model and experiment iswithin 10%, which could meet the precision of this experiment. Using this methodwe plot the growth curve of liquid seed, and choose the optimum inoculating age94-100 hours.5. Drawing the growth curve of Morchella. Under the condition of fermentingby Biostat.B, we draw the growth curve. The results indicate that Morchellafermention is a typical batch fermentation process, which contains four periods:stagnant period, fast-growth period, steady period and declining period. Due to thegrowth curve, we stop fermentation at fermentating for 120 hours. The maximumyield of mycelium reach to 13.86 g L.6. Research on the effect for fermentation of stir rate and aeration rate. Underthe condition of fermenting by Biostat.B, Applying quadric saturated D-optimalexperiment design, we established the equation between mycelium yield and stirrate, aeration rate: Y = 8. 3489?0.00014X1′ +1.04X2′+0.000012X1′2?0.00068X1′X2′?0.14X2′2.Significance test proves that the equation accord well with experiment datas. Bythe program of Matlab, we found that when stir rate is 500 r minand the aerationrate is 2.5 L min, the maximum yield is 14.06 g L.7. Research on the effect for fermentation of constant pH. Using the autosupplying system of the fermenter, acid (alkali) is added to the medium, so we cankeep constant pH (5.0,5.5,6.0,6.5) during the fermentation process. The resultsindicate that pH has obvious effect to mycelial yield. When pH is 5.5 , we canobtain the maximum mycelium yield 14.96 g L, which is 7.9% higher thannormal fermentation.8. Tracking the parameters during fermentation process. The concentration ofdeoxidize saccharides and amino azote show declining trend during the wholeprocess, the concentration of amino azote increased a little after fermentating for120h . At first deliquescent oxygen (DO) declines slowly, 24h later it declines fast,fermentating for 90h DO reach to the minimum value, 120h later it increased alittle. The minimum of DO is 46%, which proves that deliquescent oxygen isenough during the whole fermentation process. pH declines all the time, whichproves that acidic substance is created, at last pH is unaltered at 4.2. During thefermentation process we found that the mycelium yield come to the maximumnearly at the same time when degressive velocity changed from bigger to smallerof concentration of deoxidize saccharides, pH and the concentration of DO andamino azote come to the minimum. So we should terminate fermentation at thistime.9. Establishing growth kinetic model of Morchella. Comparoing Monodequation with Logistic equation as the growth model of Morchella, we chooseLogistic equation to describe the growth of Morchella and Apply GeneticAlgorithm to estimate the parameters. Establishing the growth kinetic model ofMorchella for submerged fermentation:CxCxdtdCx )= 0. 04457(1?14.01, ? ddCts =d0C. 5x7/5 d6t+0.00217Cx, the average error of this modelis 5.8%, which inosculate well with the experimental datas.