Date Published: August 21, 2015
Publisher: Public Library of Science
Author(s): Ying Luo, Jianguo Wang, Bin Liu, Zhouli Wang, Yahong Yuan, Tianli Yue, Etienne Dague.
The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry.
Patulin, which is mainly isolated from rotten fruits, may be introduced into fruit-based products during the industrial production. The presence of patulin in fruits has become a severe threat to food production and safety. Reports have implicated that patulin could induce a number of acute, chronic, and cellular-level health effects [1–3]. FAO/WHO established a provisional maximum daily intake of 0.4 μg/kg body weight for patulin because of its toxicity . Patulin, which is once considered only exist in apple products, but now, its contamination in kiwi fruit have been reported [5, 6]. The quality of kiwi fruit products have also became an increased concern.
The cell wall has been identified as the main site for mycotoxin adsorption using microbial cells . The study focused on explaining the patulin adsorption behavior based on the cell wall surface morphology and composition. Four yeast strains were used (C. tropicalis N-10, S. cerevisiae 7# and WLS-38, and Pichia anomala kurtzman B-2p) to study the patulin adsorption behavior. The micromorphology of each cell, including the cell volume and surface area, as well as the physical structure and chemical compositions of the cell wall, were observed and investigated.
The patulin adsorption capability of the yeast cell wall was mainly determined by the insoluble 1,3-β-glucan content, which forms the backbone of the network and thus determine the thickness of the yeast cell wall. Therefore, 1,3-β-glucan is an important factor that affects the patulin adsorption capability of yeast. The adsorption process could be considered as the embedment of a free patulin into a three-dimensional network structure. The patulin adsorption capability increased with increasing network density. However, to validate our hypothesis, a better methodology combining yeast cell wall network structure with patulin adsorption capability is needed. Nevertheless, this study provided experimental foundation and theoretical basis for promoting research on patulin adsorption. Moreover, juice adsorption assay indicated that inactive yeast cells could be successfully used as patulin adsorbents in kiwi fruit products.