Agricultural giant since 1983

Chapter 12: Duck Experiment
When Li Lei assisted his mentor in compiling the "Agricultural History of New China", he read the materials of Wang Shi and Zhengda Kangdi, and one detail impressed him deeply.

Wang Shi earned millions of dollars in a short period of time by supplying Northeast corn to Zhengdakang, but soon a crisis hit them.

Carcinogens were found in the chicken feed supplied by Zhengda Kangdi to Xiangjiang. Not only was Zhengda Kangdi’s feed sales affected, but even Wangshi’s corn was unsalable in large quantities, and it almost didn’t turn around.

Those materials did not point out what the carcinogen was. Li Lei only found it in Zhengda Kangdi's warehouse yesterday. It turned out to be aflatoxin.

In the summer of 1960, more than 10 turkeys died inexplicably in the suburbs of London, England. At that time, no one could tell what the disease was, so it was called "Turkey X disease"; moldy peanut powder cake, and moldy peanut powder cake contains a large amount of aflatoxin.

Scientists quickly started research on this. In 1961, it was discovered that peanut cake contaminated by Aspergillus flavus could induce liver cancer in rats. In 1962, aflatoxin was identified and proved to be a strong carcinogen.

The aflatoxin with a double bond at the end of the difuran ring in the structure is easy to form epoxidation metabolites to enhance its toxicity, carcinogenicity and mutagenicity.

Li Lei showed a plastic bag containing some moldy corn. Aflatoxins are widely distributed in nature. Among them, peanuts and corn are most likely to be polluted. This is also one of the most vigilant problems in the breeding and feed industries.

Xie Liren's expression became extremely serious, and he quickly took the plastic bag and looked at it carefully. He saw that the front color of the colony on the corn was yellow and yellow-green, and it was semi-fluffy, which is the distinctive feature of Aspergillus flavus.

"This is indeed Aspergillus flavus, but Aspergillus flavus and aflatoxin are two different things, right?" Xie Liren still had doubts.

What he said is also true. There are many types of Aspergillus flavus, and 30%-60% of the strains can produce aflatoxin.

And most non-pathogenic strains are often used in the fermentation industry as koji species, mainly for the fermentation production of some organic acids, such as Aspergillus flavus H-98 can be used for the fermentation production of L-malic acid; only see Moldy corn does not necessarily confirm that the corn is infected with aflatoxin.

"Mr. Xie is right, but aflatoxin is highly toxic and has a high carcinogenic rate. If there is a possibility, we can't ignore it. Can we conduct further testing!" Li Lei said.

Aflatoxin is extremely poisonous, and its severe toxicity is 10 times stronger than the well-known poison potassium cyanide, more poisonous than the venom of cobra and krait, and 1605% stronger than the poisonous pesticides 1059 and 28 33 times, a severely moldy corn containing 40 μg of aflatoxin can poison two ducklings to death.

In 1974, corn was the staple food in more than 200 villages in two states in western India. Due to excessive rain that year, the corn was seriously moldy. After the villagers ate moldy corn, 397 people were poisoned and 106 people died. Autopsy and pathological experiments proved that , the cause of this poisoning incident was aflatoxin B1 poisoning.

So Xie Liren didn't dare to be sloppy, and immediately called the technicians, followed Li Lei to the warehouse, and found the batch of moldy corn in the corner of the warehouse.

"Fortunately, these corns haven't been put into production yet!" Xie Liren heaved a sigh of relief after checking them out, but soon became suspicious again, "Whether it's corn from Thailand or the United States, it's impossible for the corn to be moldy when it's shipped? How is this?" What's going on?"

"When the temperature is between 24-28°C and the relative humidity is above 80%, the toxin production of Aspergillus flavus is the highest, so aflatoxin poisoning is prone to occur in spring and summer in Guangdong!" These are the basic common sense of later generations, " I guess it should be because of improper storage of this batch of corn."

"What this gentleman said makes sense." Huang Yaohong, a technician at Zhengda Kangdi, was sweating on his forehead. If Li Lei hadn't discovered it in advance, it would have been a disaster when this batch of moldy corn was put into production.

"Most of our corn is stored in special storage tanks, which can effectively avoid mildew pollution. However, due to the limited number of storage tanks, some corn can only be stored in warehouses. The humidity here is relatively high, and it will disappear after a while. It will go moldy." Generally speaking, it is still due to improper storage.

The problem did not lie in the source of supply, which meant that the damaged corn was relatively limited. Xie Liren felt a little better, "So, is there any aflatoxin in these corn? Let's do a test as soon as possible!"

This batch of moldy corn is definitely not usable, but it is still necessary to determine whether it contains aflatoxin, so that we can formulate a solution.

"Generally speaking, there are several ways to detect aflatoxins, such as thin-layer chromatography, high-performance liquid chromatography, micro-column method and enzyme-linked immunosorbent assay." Huang Yaohong looked distressed.

"However, thin-layer chromatography is cumbersome to deal with samples, the experimental process is complicated, it takes a long time, and it is easily interfered by impurities. Although I have learned it before, I am not sure about the actual operation!" His main work is not in this area.

"High-performance liquid chromatography requires a special test solution. We don't have it yet, and it's too late to buy it from RB."

"The micro-column method is to use the silicon-magnesium-type adsorbent in the micro-column tube to adsorb aflatoxin and display fluorescence under 365nm ultraviolet light, which also requires a special adsorbent."

"Enzyme-linked immunosorbent assay uses antigen adsorbents and enzyme-labeled antibodies to react specifically with the analyte in the specimen for detection, and also requires the purchase of materials."

In short, there are four methods in total. He knows the first method but is not familiar with the operation. The remaining three methods require the purchase of special chemical reagents, and they cannot be bought today and delivered tomorrow.

In addition, seeing Huang Yaohong's embarrassment, I am afraid that these chemical reagents can be delivered on time, and he may not be able to complete the operation proficiently.

Li Lei nodded slightly. What Huang Yaohong was talking about were several commonly used methods at present. In addition to these four methods, there are actually bromide fluorescence spectrophotometry and hyperspectral methods, but these methods have not yet been invented, or There are also problems with technology and testing tools, and it doesn't make sense to speak out.

Xie Liren frowned again. He was not afraid of spending money, but he couldn't afford to waste time. How long would it take to buy chemical reagents from RB and then ship them in?
"Mr. Xie, there is actually another way to carry out the test. Not only does it not take much time, but you don't need to buy additional instruments and reagents." Li Lei interjected.

"Oh? What kind of method?" Xie Liren asked quickly.

"When I was in college, I saw a paper in the first issue of "Journal of BJ Medical College" in 1974. It was about using ducklings to do aflatoxin detection experiments. I still remember the specific method."

(End of this chapter)