Research On The Effect Of Free Gossypol In Edible Fungi And The Formaldehyde Content In The Lentinus Edodes

This paper includes two parts:one is about the effects of free gossypol on growth of edible mushroom;the other is decreasing the formaldehyde content in Lentinus edodes by adding L-cysteine.(1)In order to study the effects of free gossypol on mushroom growth,the growth rates of mycelia of six kinds of mushrooms were determined after addition of free gossypol to the substrate in different concentrations;1.0,10.0,20.0,50.0 and 100.0 mg/kg.The results showed that free gossypol affected the growth rate of mycelia of all six tested mushroom species.The tolerance for free gossypol in the six mushrooms ranked:Agrocybe aegirit>Auricularia polytricha>Pleurotus eryngi>Flammulina velutiper>Pleurotus geesteranus>Pleurotus ostreatus.Next,we determined differences in free gossypol content in cottonseed hulls(used for mushroom production)from different regions,and from different factories from the same region.The contents of free gossypol varied between 172?4364 mg/kg in the tested cottonseed hulls.We then determined the contents of free gossypol in mushroom fruiting bodies by HPLC after addition of free gossypol to the substrate.The results showed that free gossypol was present in fruit bodies of Pleurotus geesteranu,Pleurotus ostreatus,Flammulina velutipes and Pleurotus eryngii,but not in Agrocybe aegirit and Auricularia polytricha.The contents of free gossypol did not increase after addition of free gossypol in higher concentrations than 1.0 mg/kg.For example,the content of free gossypol in the fruit bodies of P.ostreatus reached 96.47 mg/kg after the addition of 1.0 mg/kg,as well as after all other tested concentrations free gossypol.(2)In order to find a way to decrease the formaldehyde content in Lentinus edodes,we designed two ways to add L-cysteine to substrate of growing L.edodes mycelia;dipping and injecting.Different L-cysteine solutions(0.01,0.02,0.05,0.1,0.2 mol/L)showed that injecting L-cysteine effectively decreases the content of formaldehyde in L.edodes fruiting bodies with an optimal content and volume of 0.2 mol/L and 100 mL L-cysteine.Under these conditions,the content of formaldehyde in the fruit bodies of L.edodes was lowest(35.38mg/kg).(3)For the detection of free gossypol and formaldehyde,we optimized the parameters for HPLC.The optimal organic solvent for free gossypol was 70%acetone.Chromatographic analysis conditions for the determination of free gossypol were 40? for column temperature,a wavelength of 235 nm,and a mobile phase with:0.1%methanol to aqueous phosphoric acid 90:10,a flow rate of 1.0 mL/min and an injection volume of 5 ?L.The free gossypol standard curve equation was y=47904x-151356 with a correlation coefficient of 0.9998.The optimal conditions for formaldehyde were a mobile phase with an acetonitrile-water volume ratio of 65:35,an injection volume of 5 ?L,a column temperature of 30?,a flow rate of 1.000mL/min,a detection time of lO.Omin.The 2,4 Dinitrophenylhydrozone standard curve linear equation was y=28129x-7903.0,and the correlation coefficient was 0.9998.