br Conclusion br Conflict of interest

Conclusion
Conflict of interest
Acknowledgments The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the research group project No. RGP-120.
Introduction
Methods
Results
Conclusions
Introduction Patulin (α, β-unsaturated-γ-lactone) is a toxin secondary metabolite produced by several fungal species belonging to the genera Penicillum, Aspergillus and Byssochlamys (Sant\'Ana, Rosenthal, & de Massaguer, 2008). It can be found in a number of fruits, including apples, pears, grapes, apricots, strawberries, peaches, and frequently occurs in commercial 3-isomangostin sale juices especially apple juice (Schumacher, Müller, Metzler, & Lehmann, 2006). It is demonstrated that patulin contamination could pose a serious health risk to consumers, and various forms of acute and chronic effects of patulin have been characterized (Iwahashi et al., 2006, Moake et al., 2005). Because of its toxicity, the Joint FAO/WHO Expert Committee on Food Additives set the provisional maximum tolerable daily intake for patulin at 0.4 μg/kg body weight/day (FAO/WHO (Food and Agricultural Organization/World Health Organization), 1995, Janotová et al., 2011) and the maximum tolerance limit in apple juices was set at 50 μg/L (FAO/WHO (Food and Agricultural Organization/World Health Organization), 1995, FDA (Food and Drug Administration), 2001). Additionally, the maximum permitted levels of patulin has been set at 50 μg/L for fruit juice in 2006 by the European Union (Commission regulation, 2006). The patulin in the apple juice was obtained from the rotten apple, which is contaminated by penicillium expansum. The known strategies for detoxification of patulin in apple juice include physical, biological and chemical methods. Propylthionl functionalized SBA-15 was found to reduce patulin levels in aqueous solutions, including contaminated apple juice (Appell, Jackson, & Dombrink-Kurtzman, 2011). About 1 kGy of gamma irradiation was found to be effective for the reduction of patulin, but the nutritional elements should be considered because the radio-degradation effects are environment dependent (Yun et al., 2008). In the meantime, caustic treated waste cider yeast (S. cerevisiae) had been successfully used as a biosorbent for the removal of patulin from apple juice (Guo et al., 2013). Oxidation by potassium permanganate in acidic and alkali conditions also resulted in better than 99.99% patulin reduction in laboratory waste (Fremy et al., 1995, Moake et al., 2005). However, more and more attention was paid on biosorbent due to its low cost. In addition, it is easy to get effective biosorbent by grafting special chemical groups, which is the source of different functional groups such as amine, hydroxyl, sulfonate, carboxyl and phosphate (Niderkorn et al., 2007, Yuan et al., 2014, Zhao et al., 2011). These functional groups have been reported to be responsible for mycotoxin binding. Herein, we reported the development of chemically modified chitosan resin to remove patulin from apple juice. Chitosan is a linear polysaccharide composed of randomly distributed β-(1-4)-linked d-glucosamine and N-acetyl-d-glucosamine, obtained by the alkaline, partial deacetylation of chitin, which originates from shells of crustaceans such as crabs and prawns (Li et al., 2015, Rinaudo, 2006, Sankararamakrishnan and Sanghi, 2006). Chitosan has drawn particular attention as effective biosorbent due to its low cost compared with activated carbon and its high contents of amino and hydroxyl functional groups showing high adsorption potential for various mycotoxin (Bhatnagar & Sillanpää, 2009). However, chitosan can be dissolved in acid media and its applications are limited (Zhou, Liu, & Liu, 2009). The cross-linked chitosan polymers were found not only to enhance the resistance to acid media, but also to improve its adsorption capability, which overcome its limits in the practical application (Crini, 2006, Zhao et al., 2015). Various reagents, including glutaraldehyde, epichlorohydrin, ethylene glycol diglycidyl ether and tripolyphosphate etc. have been used to synthesize chitosan polymers and to stabilize it in acidic solutions whereby the reaction occurs through the Schiff\'s base reaction between aldehyde groups of glutaraldehyde and some amine groups of chitosan (Huang et al., 2009, Martinez et al., 2007, Sankararamakrishnan and Sanghi, 2006). A study showed that cross-linked chitosan–glutaraldehyde complex was an excellent adsorbent for the simultaneous adsorption of multiple mycotoxins in vitro (Zhao et al., 2015). Meanwhile, it was found that xanthated chitosan could be an excellent adsorbent for the removal and recovery of cadmium ions from electroplating wastewater where cyanide ions are the main interfering ions (Sankararamakrishnan, Dixit, Iyengar, & Sanghi, 2006). The xanthated modification could improve the content of sulfydryl groups in chitosan resin, which has good adsorption properties for patulin (Li et al., 2015). But there are no studies on the application of xanthated chitosan resin for removal of patulin from apple juice.