| Deoxynivalenol(DON)is a common mycotoxin produced by Fusarium graminearum.Its contamination of cereals is the most prevalent among Fusarium toxins and poses a serious threat to human and livestock health.China is one of the countries with serious DON pollution.Due to DON’s strong toxicity and chemical stability,there are currently no efficient methods for controlling DON contamination under high temperature and strong acid conditions during grain processing.Therefore,developing DON adsorbents that can be applied under these conditions could help reduce DON contamination in the grain processing and feed industries.The main research areas are as follows :(1)Based on wheat samples from Jiangsu Province,a Gram-negative bacterium capable of reducing DON content in an acidic environment was isolated and named ASAG-D25.Studies were conducted on the carbon source metabolism and growth characteristics of ASAG-D25.The optimum growth conditions of ASAG-D25 were determined to be LB medium at 30 ℃ with a culture rotation speed of 200 r/min and a p H of 7.0.(2)The whole gene sequencing analysis of ASAG-D25 was carried out,and the fine genome map was drawn.The genome prediction and annotation and corresponding functional analysis were completed.The COG classification of secretory proteins,metabolic pathways,transporters and genome-encoded proteins were predicted and analyzed.The genome size of ASAG-D25 was 4299756 bp and the GC content was 57.93 %.It contains 4133 predicted genes.The full length of the coding gene was 3783105 bp,and the average length was 915.Among them,there are12 r RNAs and 62 t RNAs.The annotation of the general database shows that ASAG-D25 has the ability of benzoate degradation,pyruvate metabolism,methane metabolism and so on.(3)The optimization of extracellular polysaccharide(EPS)production conditions of ASAG-D25 and the test of EPS adsorption DON ability were carried out.When the carbon source was 40 g/L glucose and the nitrogen source was 0.5 g/L ammonium chloride,the optimum conditions for EPS synthesis were determined.The adsorption test showed that EPS had poor adsorption capacity for DON.The subcellular components were obtained by treatment with various biological enzymes,and the cell surface functional groups were treated with chemical reagents.It was determined that the cell wall accounted for the main role of adsorption.It was speculated that the hydroxyl,carboxyl and ester bonds on the cell surface were involved in the adsorption of DON.Further analysis of the factors affecting the adsorption of DON by bacteria :the type of medium,the amount of bacteria,p H,reaction temperature and initial concentration of DON were evaluated to find the best adsorption reaction conditions.The results showed that using LB liquid medium at p H 7.0 with a reaction temperature of 30℃ with a dry weight of 0.14 mg/m L system cells and an initial concentration of DON at 5 μg/m L were optimal conditions.The adsorption kinetics and adsorption thermodynamics of DON adsorbed by bacteria were studied to determine the type of adsorption reaction.The results of adsorption kinetics showed that the pseudo-second-order kinetic model was more suitable for describing the adsorption process.The adsorption thermodynamics showed that the Langmuir thermodynamic model was more consistent with the adsorption process,which was monolayer adsorption.At present,there are few studies on DON adsorbents.Traditional methods such as physical chemistry have many limitations in practical applications,and crops are subject to a large range of DON pollution.Therefore,it is particularly important to develop green and safe DON biosorbents for food processing,which provides new ideas for DON pollution in food processing industry. |
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