Spatial and compositional variation in the fungal communities of organic and conventionally grown apple fruit at the consumer point-of-purchase

The fungal diversity in harvested apples from organic or conventional management practices was analyzed in different fruit locations(stem end,calyx end,peel,and wounded flesh)shortly after fruit purchase(T1)and after 2 weeks of storage(T5).A total of 5,760,162 high-quality fungal sequences were recovered and assigned to 8,504 Operational Taxonomic Units.Members of the phylum Ascomycota were dominant in all samples and accounted for 91.6%of the total number of detected sequences.This was followed by Basidiomycota(8%),Chytridiomycota(0.1%),and unidentified fungi(0.3%).Alpha and beta diversity analyses revealed the presence of significantly different fungal populations in the investigated fruit parts.Among detected fungi,the genus Penicillium prevailed in the peel and in the wounded flesh while Alternaria spp.prevailed in the calyx and stem end samples that included apple core tissues.Several taxonomic units that appear to be closely related to pathogenic fungi associated with secondary human infections were present in peel and wounds.Moreover,significantly different populations were revealed in organic and conventional apples and this result was consistent in all investigated fruit parts(calyx end,peel,stem end,and wounded flesh).Several unique taxa were exclusively detected in organic apples suggesting that management practices may have been a contributing factor in determining the taxa present.In contrast,little differences were revealed in the two assessment times(T1 and T5).Results of the present study represent an advancement of the current knowledge on the fungal microbiota in collected fruit tissues of apple.

High-Throughput Screening of Nanoparticle-Stabilizing Ligands:Application to Preparing Antimicrobial Curcumin Nanoparticles by Antisolvent Precipitation

Water-dispersible curcumin nanoparticles were prepared by bottom-up antisolvent precipitation approach. A new high-throughput screening technique was developed for selecting appropriate ligands stabilizing the nanoparticles in aqueous medium and improving their performance. The initial set of twenty-eight potential stabilizing ligands was evaluated based on their capacity to improve curcumin dispersibility in aqueous medium. The performance of four promising ligands(amino acid proline, polyphenol tannic acid, polycation Polyquaternium 10, and neutral polymer polyvinylpyrrolidone) was tested in ultrasound-aided antisolvent precipitation trials. Using the selected stabilizing ligands diminished the average particle size from ca. 1,200 to 170–230 nm, reduced their dispersity, improved stability, and allowed reaching curcumin concentration of up to 1.4 m M in aqueous medium. Storage stability of the aqueous nanodispersions varied from 2 days to 2 weeks, depending on stabilizing ligand. Studying the effects of ionic strength and pH on size and f-potential of the particles suggested that electrostatic forces and hydrophobic interactions could be the major factors affecting their stability. The ligand-protected nanoparticles showed minimal inhibitory concentration of 400 or500 μM toward Escherichia coli. We suggest that the presented screening approach may be useful for preparing nanoparticles of various poorly water-soluble bioactive materials.

亚致死氧化胁迫锻炼对橄榄假丝酵母（Candida oleophila）抗氧化基因转录表达、抗逆性及生物防控的增效作用

采用5mmol／L浓度的H202对橄榄假丝酵母（Candida oleophila）预处理30min，结果表明，这种亚致死胁迫处理可增强橄榄假丝酵母对于之后的致死胁迫处理（50mmol／LH202，40℃，pH4）的耐受力。与对照相比，经亚致死胁迫处理的酵母菌对于接种于苹果果实上的扩展青霉菌和灰霉菌具有更好的抑制活性，且在果实伤1：2处接种初期具有较快的生长繁殖速度。采用抑制性消减杂交技术研究了酵母菌在基因表达水平上对于亚致死氧化胁迫的响应,并利用半定量RT—PCR技术明确了其转录水平。结果表明，亚致死氧化处理使酵母菌中的7个抗氧化基因发生了上调,这些基因的高表达与经胁迫处理的酵母菌中活性氧积累的减少及脂质过氧化产物含量的降低有密切联系。说明对具有生物防控能力的酵母菌采用非生物压力胁迫，可提高其中与抗氧化胁迫相关的基因表达，从而提高其生物防控效果。