Screening Of Ochratoxin A Producing Fungal On Grapes And Studing Of The Possible Mechanisms Involved In Toxin-Production

Ochratoxin A(OTA) is mainly produced by the genera Aspergillus and Penicillium. Studies showed that OTA can have several toxic effects.Worldwide, OTA contamination of grapes and its derived products is an enormous threat to the health of human, plants and animals. Many studies have been conducted on the control of OTA and biological method is currently gaining more attention due to its safety to human and environment. A good knowledge of the causes of OTA and the mechanism involved in its production is the foundation to a successful biological control. With the development of molecular biology, some new methods have been applied in mechanism research and some new types of rapid molecular detection and control methods have been developed alone with uncovering part of OTA biosynthesis pathway and mechanism. The distribution of a wide range of OTAproducing strains vary with region, climate and food stuff. Researchers need to enrich the OTA-producing strains database in order to find effective broad-spectrum methods to control the toxin.The Objectives of this study were to investigate:(1) the potential of some fungi isolates from a vineyard to produce OTA.(2) the effect of temperature and pH and on OTA producing fungi and(3) the differentially expressed proteins of the P.griseofulvum cultured under different pHThe OTA-producing strains were isolated from an organic vineyard in Zhenjiang Jurong and preserve in our laboratory.subsequently screened for their ability to produce OTA The potential ochratoxin A(OTA) producing strains were first screened by fluorescence and then detected by High Performance Liquid-fluorescence(HPLC-FLD), Then LC-MS was used to identify the metabolites. The OTA produced by Penicillium griseofulvum and the mechanism of production was studied through comparison of proteins and genes expression differences between the toxin-producing promoted and restrained conditions. The main results were listed as follows:1. Among the OTA-producing fungi isolated, the highest producing strain was X9-4 isolated from rotten Jufeng grape cultivar. It was identified as Penicilliumgriseofulvum by analyzing the 5.8S r DNA-ITS sequence as well as its morphological physiology.2. The results indicated that the optimal temperature for Penicillium griseofulvum was 25 °C in the CYA medium. At this this temperature, the fungi produced the highest OTA at a pH=5 cultured in dark. The findings showed that P.griseofulvum could not grow at low and high temperatures, and the toxin-production was restrained under such conditions including extreme acidic or alkaline and lighting environment.3. Some toxin-biosynthesis related proteins were identified, the proteins associated with toxin-producing belong to the basic metabolism and synthesis related protein, energy supply related protein, stress protein, transport protein, and regulatory protein.4. It was found that OTA synthesis was restricted under low pH due to low expression of some mycotoxin synthesis related enzymes in metabolic pathways. This was determined through the analysis of the transcriptome data of p.griseofulvum.Expression of some genes regulating toxin synthesis pathways were also reduced under acidic culture condition.