Screening Of High-yielding Strain In Cordycepin And Study On The Fermentation Technology In Cordyceps Militaris

Cordyceps militaris (L.Fr) Link.is one of the precious traditional Chinese medicineswith high value for medicine and economy purposes, which belongs to Ascomycota,Pyrenomycete, Sphaeriales, Clavicipitaceae and Cordyceps.The object of this work is to obtain one cordyceps strain with high yield ofcordycepin from 9 candidate strains of cordyceps. The media of liquid fermentation,culture condition and liquid fermentation technology were optimized and the yield ofcordycepin was elevated prominently, reaching almost 3000μg/ml. Theseexperimentations put forward the industrial production of cordycepin.1. Using the same medium and fermentation technology, 9 strains were screened for theyield of cordycepin. The result showed No.8 was the strain with the highest yield.2. There are 5 factors which can influence the fermentation of cordycepin: seed sources,the time of submerged fermentation, the time of surface fermentation, inoculum sizeand the initial pH. After optimization of the five factors individually, the improvedtechnics was as follows: the suspension of conidium was prepared as seed after 15days plate culture away from light plus 5 days culture with illumination, thefermentation cycle was 20 days including 4 days of submerged fermentation and 16days of surface fermentation, the inoculum size was 2%(suspension of conidium (3.2×10~9/ml)), the initial pH was 6.45-6.95.3. Using the concentration of cordycepin and the weight of mycelium as indicators,carbon sources and nitrogen sources were screened and an optimized medium was asfollows: 5% of glucose, 5% of soybean meal.4. To obtain the optimized medium, the orthogonal test of glucose, soybean meal, potatoextract and adenosine was carried out. The results showed that the four factors all hadsignificant influence on the fermentation of cordyceps. The optimized medium was:2% of glucose, 8% of soybean meal, 2% of potato extract and 0.4% of adenosine.5.0.6% of adenosine was considered as the optimal concentration of adenosine throughthe verification of single factor test. 2% of glucose was considered as the optimalconcentration through the verification of single factor test.6. This research demonstrated that the submerged fermentation technology combined withthe surface fermentation could favor the growth of Cordyceps in the liquid medium. High biomass density could be reached and the biosynthesis of cordycepin could bepromoted in the late stage of growth.7. The precursor of cordycepin, adenosine was added into the liquid medium forexperiment. The results indicated that the addition of adenosine could reinforce theCordysceps’s ability of transformation of adenosine into cordycepin when the initialconcentration of glucose was low. The elevation of concentration of soybean mealcould further strengthen the transformation ability of Cordysceps. A large amount ofadenosine is demanded when Cordysceps produces cordycepin. The ability ofbiosynthesis of adenosine of Cordysceps is limited and extra adenosine needs to beadded into the medium appropriately to improve the productivity of cordycepin. In thefuture, how to improve the transformation ability of cordysceps is one key object.