The Diversity And Edible Safety Of Yeasts On The Surface Of Apple And Pear

Apple and pear are staple and characteristic fruit in North in China, whose outputalready rank first. There is a risk of corruption that apple and pear as fresh food aresusceptible to being polluted by microorganism during transportating or storing. Yeastis unicellular fungi and one of the epiphyte on the surface of fruit, a few of them arehuman pathogens, meanwhile it is one of the main objects of food satefy testing. Atpresent, evaluation system of harmfulness about yeast on the surface of fruit in Chinais not sound.So it is important to study the diversity of yeast on the surface of fruitand its edible safety for detection, prevetion and control of foodborne pathogenicmicroorganism.214yeast strains were isolated from apples and pears skin producted in theprovince of Shandong, Hebei, Anhui, Shanxi, Gansu and Sinkiang. These strains wereidentified by the26S rDNA D1/D2domain sequence analysis on the base ofmorphologic characters.16genus24species were identified: Candida intermedia,C.pseudointermedia,C. quercitrusa,C. railenensis, C.sp., C.zemplinina, Cryptococcusflavescens, Debaryomyces hansenii, Hanseniaspora uvarum, Issatchenkia orientalis,Kodamaea ohmeri, Lodderomyces elongisporus, Metschnikowia pulcherrima,Meyerozyma guilliermondii, Occultifur aff.externus, Pichia anomala, P.fermentans,P.kluyveri, P.mexicana,Pseudozyma aphidis,Rhodotorula mucilaginosa, Sporidioboluspararoseus, Torulaspora delbrueckii and Wickerhamomyces subpelliculosa. The resultshowed that the surface of apples and pears has abundant yeast resources.The cell cytotoxicity of fermentation liquid of24different yeast strains to humanesophageal cancer cells Eca-109, human lung carcinoma cells A549and human breastcancer cells mcF-7was researched by MTT method. The result showed that thestrains YTFSFL-2(Candida zemplinina), YTLYSJL-2(Rhodotorula mucilaginosa),YTQXHFS-4(Pichia mexicana), JNFSL-2(Hanseniaspora uvarum), QDFS-3(Cryptococcus flavescens), BZYXYL-2(Meyerozyma guilliermondii) and JNHJL-1(Debaryomyces hansenii) had obvious inhibitory effect on human esophageal cancercells Eca-109, the inhibition rate range of the seven trains was from49.406%to74.352%, YTLYSJL-2among of them had the highest inhibition rate. The strainsYTFSFL-2, YTQXHFS-4and JNHJL-1had obvious inhibitory effect on human lung carcinoma cells A549, the inhibition rate range of the three trains was from24.593%to39.692%, YTQXHFS-4had the highest inhibition rate. The strains YTQXHFS-4,JNFSL-2, JNHJL-1, QDFS-3and BZYXYL-2had obvious inhibitory effect on humanbreast cancer cells mcF-7, the inhibition rate range of the five trains was from22.868%to72.894%, JNHJL-1had the highest inhibition rate, up to42.894%. So theseven yeast strains were screened for further screening. Their fermentation liquid allhad obvious inhibitory effect on glomerular mesangial cells HEZY-1, the inhibitionrate range was from22.868%to42.894%, therefore the inhibitory effect ofYTQXHFS-4and JNHJL-1was more obvious than the others, their inhibition rateswere respectively79.874%and68.682%, meanwhile the two strains had obviousinhibitory effect on the three cancer cells obove, their inhibition rates wererespectively54.093%,39.692%,70.888%and49.406%,24.593%,72.894%. The last,the two strains YTQXHFS-4and JNHJL-1were screened as candidate pathogenicstrains, which would provide materials for toxicology, pathology and so on.