Effects Of Light On Growth And Toxin Synthesis Of Aspergillus Flavus

In this article,Aspergillus flavus was taken as the research object,blue,yellow,green,and red LED light was used to treat Aspergillus flavus.The microscopic,submicroscopic structure,utilization rate of nutrient,intracellular oxidoreductase activity,and aflatoxin content of Aspergillus flavus were studied in order to reveal the effects of light on growth and mycotoxins synthesis of Aspergillus flavus,the main findings are as follows:?1?The light had the role of regulating Aspergillus flavus growth and development.Blue and yellow light might inhibite the germination of Aspergillus flavus and green and red light might stimulate the germination of Aspergillus flavus,significantly.The germination capacity of Aspergillus flavus treated with blue light?1500 lx?was lost completely,the number of colony of Aspergillus flavus treated with yellow light?15281.0 lx?decreased by24.1%compared with the control group after 48 hours of continuous culture.The number of colony of Aspergillus flavus treated with green light?6676.47 lx?and red light?1921.64 lx?increased by 33.92%and 25.00%compared to the control group,respectively.The studies on microscopic and submicroscopic structure of Aspergillus flavus showed that blue light can cause damage to cell walls,cell membranes,and organelles of Aspergillus flavus,increase the number of mitochondria,and cause intracellular environmental congestion.?2?The light might influence the nutrients absorption and utilization of Aspergillus flavus.The blue light and yellow light might help reduce the absorption of sugar and protein of Aspergillus flavus,and green and red light help facilitate the absorption of sugar and protein of Aspergillus flavus,significantly.Compared with the control group,the utilization rate of reducing sugar of the blue light treatment group?B,750 lx?and the yellow light treatment group?Y,15281.0 lx?decreased by 22.8%and 8.01%,protein utilization rate decreased by 32.4%and 19.6%,respectively.Compared with the control group,the reducing sugar utilization rate of green light treatment group?G,6676.47 lx?and red light treatment group?R,1921.64 lx?increased by 10.68%and 11.16%,respectively,green and red light treatment had similar effect on protein utilization rate.The early stage of the growth?less than 20 h?is a key period when light had a crucial effect on the absorption of nutrients of Aspergillus flavus.Light might affect the activity of SDHase of Aspergillus flavus.Blue light and yellow light might inhibit SDHase of Aspergillus flavus,green and red light might increase SDHase activity of Aspergillus flavus.Compared with the control group,blue light?750 lx?and yellow light?15281.0 lx?can reduce SDHase activity by 47.00%and 25.55%,green light?6676.47 lx?and red light?1921.64 lx?can increase SDHase activity by 22.90%and21.85%,respectively.The light quality has significant effect on MDHase activity of Aspergillus flavus after 48 hours of continuous culture.Compared with the control group,there were significant differences in B,G,and R.The MDH enzyme activity in group B was reduced by 6.54 U?8.3%?,Y group was equal to CK group,and G,R was increased by 9.8 U?increased by 12.5%?.It can be seen that the light quality has less effect on MDH enzyme activity than SDH.?3?A HPLC-MS/MS measurement method was developped for analysis 10 kinds of mycotoxins including aflatoxin B₁,B₂,G₁,G₂,cyclopiated acid,penicillic acid,patulin,sterigmatocystin,citrinin,penicillin.The method had a wide linear range,the recovery of the method was between 80-120%,and RSD is lower than 8%.The light might influence synthesis of mycotoxins of Aspergillus flavus.Compared with the control group,the contents of AFB₁,AFB₂,CPA,STR,AFG₁ and AFG₂ of B group?750 lx?decrease by 96.33%,91.56%,92.27%,90.74%,61.78%,28.22%,and Y group?15281.0 lx?decrease by 89.00%,75.58%,92.27%,90.74%,61.78%,45.41%,respectively.Compared with the control group,the contents of AFB₁,AFB₂,STR,AFG₁ and AFG₂ of G group?6676.47 lx?increased by 22.37%,21.81%,42.96%,61.11%and 33.06%except for a8.7%decrease in CPA,the contents of AFB₁,AFB₂,CAP,STR,AFG₁ and AFG₂ of R group increased by 68.51%,5.73%,2.2%,58.15%,54.86%and 34.68%,respectively.