The Detoxifying Capability And Mechanisms Of Zearalenone By Planococcus Sp. S118

Zearalenone (ZEN) is a non-steroidal secondary metabolite with estrogenic-like effects which can be produced by several Fusarium species. Throughout the world, ZEN has been detected in a number of cereal crops such as maize, barley, oats, wheat, rice, sorghum, and rye. ZEN has been shown to cause a variety of toxic effects in animals and humans.In this paper, we successfully identified a bacterial isolate which has capability to detoxify ZEN. Then we conducted a research on the detoxifying capability, detoxifying mechanisms and factors affecting detoxifying efficiency of the bacterial isolate.This study can be divided into three parts. The first part was screening for bacteria which has capability to detoxify ZEN. One of the obtained bacterial isolates exhibited detoxifying capability. After DNA extraction, PCR-mediated amplification of the 16S rDNA, and purification and sequencing of the PCR products, it was revealed that the isolate belonged to the genus Planococcus sp. The isolate was named as Planococcus sp. S118 by our lab.In the second part, the detoxifying capability and detoxifying mechanisms were investigated. After 24 h of culturing S118 with ZEN, the bacteria exhibited strong detoxifying capability not only by viable bacteria (21.82%) but by heat-inactivated bacteria (47.82%) as well. No degradation products of ZEN were observed by HPLC. After disintegrating the cells using ultrasonic, the cell wall fraction was capable of detoxifying ZEN, but the cell extract nearly failed to detoxify ZEN at the same time. Heat, acid, and Triton-100 treatment significantly enhanced the bacterial capability to remove ZEN. All of this indicated that ZEN was probably binding to the cell bacteria, causing the ZEN to reduce from incubation mixtures.The last part was to investigate the impact of incubation time, bacterial concentration, temperature, pH value and ZEN analogues, which were factors affecting detoxifying efficiency. The detoxification of ZEN was a relatively rapid and continued process since approximately 16.43% and 34.59% ZEN were removed after mixing with either viable bacteria or heat-inactivated bacteria. When incubation was continued, the percentage of ZEN detoxified was increased. The detoxifying capability of ZEN relied strongly on the concentration of bacteria in the incubation mixtures. The higher the concentration of bacteria was, the greater difference between viable bacteria and heat-inactivated bacteria was. Meanwhile, low pH value would increase the detoxify capability of S118. While the pH value dropped from 8.5 to 4.5, the absorption percentage of ZEN increased from 12.04% to 31.75% by viable bacteria and from 23.19% to 43.98% by heat-inactivated bacteria. The best incubation temperature was 30℃. The S118 could likewise remove Zearalanone (ZAN, one of the ZEN analogues) and had a higher affinity percentage to ZEN than to ZAN. A competitive adsorption existed between ZEN and ZAN.All the three parts of experiments showed that S118 had significantly detoxifying capability of ZEN in the incubation mixtures. Binding rather than metabolism could possibly explain the interaction of Planococcus sp. S118 with ZEN. The detoxifying efficiency was affected by incubation time, bacterial concentration, temperature, pH value and ZEN analogues. These studies offered a potential approach to reduce the intestinal absorption of ZEN from human diet and animal feeds.