Team:NPU-CHINA/Description
DESCRIPTION
Aflatoxin B1 was designated as a class Ⅰ carcinogen by the World Health Organization cancer research agency in 1993. It is highly toxic and not easy to be decomposed. Aflatoxin can be enriched in livestock through feed, which could affect agricultural and sideline products, and even enter the human body through food. Ultimately, the enriched aflatoxin might seriously damage human liver function.
Aflatoxin contamination in food spread to all regions of the world. Its content is strictly stipulated in the Feed Health Standard (GB13078-2017). The allowable amount of aflatoxin B1 (μg/kg) in the raw materials of products is ≤50, while it is generally ≤20 in all kinds of concentrated feed.
The the corresponding survey shows that the feed, such as corn and its by-products, oil meal and cakes, and distillers driven grains with soluble, is polluted by aflatoxin B1, and the exceeding rate is more than 10%.
At present, the mixture of raw materials with different aflatoxin content at a specific ratio was the main approach adopted by enterprises to decrease the aflatoxin content in the feed. Addition of the aflatoxin adsorbent, which is not digested and absorbed by livestocks, is another method to solve the problem of the excessive aflatoxin. However, these two methods can not completely solve the problem of aflatoxin pollution. The undegraded aflatoxin may still cause secondary pollution.
Therefore, our team dedicated to develop a safe and efficient feed additive to directly degrade aflatoxin in feed. Bacillus subtilis, which is generally considered safe, was selected as as a carrier to assemble aflatoxin degradation proteins, stable-phase promoters and self-cleavage protein in our project. The engineered Bacillus subtilis is given the ability to self cleave and release aflatoxin degrading protein in the stable period, which could enhance the ability of the designed system to degrade aflatoxin and eliminate engineering bacteria in feed, simultaneously.
In addition, it was accidentally found that sodium selenite is a commonly used selenium additive in feed. However, sodium selenite has inherent defects such as low biosafety and low bioavailability as an inorganic selenium additive. It was reported that organic nano-selenium is expected to replace the inorganic selenium as a commonly used selenium additive in feed.
Based on the above discussion, combined with the selenium-enrichment function of Bacillus subtilis, our team dedicated to construct a strain of intelligent Bacillus subtilis with self cleavage function, which can simultaneously degrade aflatoxin and enrich organic nano-selenium. Finally, a new, safe and selenium rich high-value feed additive is provided.
Reference：
[1]GB 13078-2017饲料卫生标准[J].饲料与畜牧,2018(01):16-24.
[2]侯楠楠,谢全喜,王梅,王倩,谷巍.2019年全国部分地区饲料及原料霉菌毒素污染状况调查[J].广东饲料,2020,29(10):47-50.
[3]计成,马秋刚,赵丽红,贾如. 由枯草芽孢杆菌分泌的黄曲霉毒素降解酶及其应用[P]. 北京市：CN107760655B,2021-02-26.
[4]康振,陈坚,堵国成,杨森. 一种稳定期自裂解的枯草芽孢杆菌及其应用[P]. 江苏省：CN106244613B,2019-05-17.
[5]Xu C, Qiao L, Guo Y, Ma L, Cheng Y. Preparation, characteristics and antioxidant activity of
polysaccharides and proteins-capped selenium nanoparticles synthesized by Lactobacillus casei ATCC
393. Carbohydr Polym. 2018 Sep 1;195:576-585.
[6]Xu C, Qiao L, Ma L, Yan S, Guo Y, Dou X, Zhang B, Roman A. Biosynthesis of
Polysaccharides-Capped Selenium Nanoparticles Using Lactococcus lactis NZ9000 and Their Antioxidant
and Anti-inflammatory Activities. Front Microbiol. 2019 Jul 26;10:1632. doi:
10.3389/fmicb.2019.01632. PMID: 31402902; PMCID: PMC6676592.
CONTACT NPU CHINA
NPU-CHINA is the iGEM team of Northwestern Polytechnical University
Address: 127 West Youyi Road Beilin District, Xi'an,
Shaanxi 710072, China
Contact: npuigem@outlook.com
bilibili: NPU-iGEM
