Isolation And Identification Of Patulin-producing Strains From Pears And Their Growth Characteristics

Pear (Pyrus spp), one of three yield fruits in China, has rich varieties resources. Patulin(PAT) is a kind of secondary metabolite of fungal toxins, which is teratogenic, carcinogenicand mutagenic to animals. Since joined the WTO, patulin residue has become an importantfactor of affecting pear juice quality and safety, also limiting Chinese juice internationalmarket competitiveness. Although some success on patulin controlling techniques in juiceproduction and processing have been made, we haven’t resolved the problem radically andlacked practical control technique yet. Patulin in pear products is mainly from thecontamination of patulin-producing strains. So in-depth and extensive research on inhibitingpatulin-producing strains growth and producing patulin have theoretical and practical impacton improving the technical level and product quality, and pear process industry development.In this paper, patulin-producing strains were isolated from pears which which belong todifferent types and areas, and were identified by morphological and ITS（Internal transcribedspacer）sequences analysis. The growth and metabolic characteristics of one of the mainpatulin-producing strain were studied, by different medium, pH and culture temperature.Effects of hot water and chlorinedioxide on stains growth were also taken into considerationsas well. The main results and conclusions were as follows.1. The isolation and identification of the main patulin-producing strains from differentvarieties.10patulin-producing strains were isolated from decayed Yang Xin and Lai Yangpears. By morphological characteristics we concluded7strains were Penicillium,2strainswere Aspergillus, and1strain was Fusarium. By ITS sequences analysis we got reliableresults: Penicillium sp.8-9, Penicillium purpurogenum strain F43, Penicillium sp.4382,Aspergillus sp.CRCF11, Penicillum sp.3TMS-2011voucher BGd100p3-1, Penicilliumfuniculosum isolate NG_p14, Aspergillus versicolor strain A11.2, Penicillium polonicumstrain F5, Fusarium sp.NRRL4490and Penicillium sp.12-20. Phylogenetic tree showed that10patulin-producing strains from decayed pears have different levels of the phylogeneticrelationship. From that we know Penicillium is the main contamination fungi that result inpatulin problem in pears, and the P-1has the strongest ability.2. The growth and patulin production of P-1. The results showed that there weresignificant difference in growth and patulin production of P-1during different conditions. Inliquid CA medium: the lower initial medium pH, the higher PAT produced, and the mediumpH had an increasing trend during the cultivation, which may be the reason cause PATdecomposition. There were no significant difference in final weight of dry BC under different conditions. In pear juice medium: the medium pH had a decrease trend, and there were nosignificant difference in final weight of dry BC under different culture temperature, theweight of dry BC reached maximum value under the condition of35℃,11d. The optimumPAT production temperature is25℃. The different environment made the difference of growthand patlin-production of P-1.3. The control of P-1growth. Hot water and chlorinedioxideo provided significantcontrol of P-1growth in there conditions. The higher temperature of the water, the betterinhibition effect we got.55℃,20min provided significant difference on P-1growth. Thehigher the concentration of chlorinedioxideo, the better the P-1growth is controled.