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  • The proposed method was also used

    2023-05-15

    The proposed method was also used to evaluate resistance to natamycin (a natural antibiotic produced by Streptomyces natalensis used for fungal control on cheese surface) of 9 fungi, including those previously mentioned as well as Phoma pinodella UBOCC-A-116004, Candida parapsilosis UBOCC-A-216002, Meyerozyma guilliermondii UBOCC-A-216003, Trichosporon asahii UBOCC-A-216005, and Rhodotorula mucilaginosa UBOCC-A-216004 (Garnier et al., 2017). Natamycin resistance was tested in a similar concentration range (from 0 to 0.2 mg/dm2) as that used by Garnier et al. (2017). Natamycin was deposited on the mini-cheese surface, in duplicate, using 100 µL of a stock solution followed by fungal inoculation on the cheese surface as described above. The MIC was determined as the concentration for which no visible growth occurred after the incubation period (Table 2). The obtained MIC values were then compared with those obtained by Garnier et al. (2017) in potato dextrose agar at pH 5. Independently of the fungal target, natamycin MIC were generally slightly lower in the cheese model than in potato dextrose agar. This result may be explained by differences in the physiological status of the fungal targets as well as by the fact that other compounds present in the cheese may enhance natamycin activity. For example, lactic BMS 195614 produced by lactococci starter cultures could act synergistically with natamycin. Mucor racemosus and T. asahii were the most sensitive fungi to natamycin with a MIC of 0.04 mg/dm2, followed by P. commune (0.06 mg/dm2; Table 2). Yarrowia lipolytica showed the highest resistance to natamycin with a MIC of 0.16 mg/dm2, which is very close to the maximum authorized concentration (0.2 mg/dm2) that can be used in dairy products within the European Union.
    ACKNOWLEDGMENTS
    Introduction Paper currency is a public health risk when associated with the simultaneous handling of food, leading to spread of nosocomial infections. The previous research reported that the banknotes were contaminated with either bacteria or fungi (Honua, 2017). In order to decrease the public health risk, various additives such as antibacterial and antifungal agents could be added to the banknote papers. Nanotechnology is an approach that can be used to produce antimicrobial coatings on the papers. The nanomaterials, not only improve specific mechanical, physical, and chemical properties, but also serve as carriers for some active substances, such as antioxidants and antimicrobial agents (Yien, Zin, Sarwar, & Katas, 2012). Adding these nano-size additives could also increase the durability of the final products. In the recent years, inorganic nanomaterials have been used as antifungal agents, but concerns regarding their negative effects on human health restrict their applications as antimicrobial agents (Ahamed, AlSalhi, & Siddiqui, 2010; Gopalan, Osman, Amani, De Matas, & Anderson, 2009). Chitosan is considered as an antibacterial and antifungal agent. Due to its similar structure to the cellulose, the applications of chitosan have been received attention in the paper making industry. In a dilute acidic solution, −NH2 groups of chitosan transforms into a polycation, leading to better absorption to an anionic pulp by electrostatic interactions. This characteristic makes chitosan an ideal wet-end functional additive in paper making (Tsigos et al., 2000). There has been a growing interest in using chitosan as a coating material for various applications, because of its remarkable film-forming (Aider, 2010). Antifungal activity is one of the most important bioactivities of chitosan, and earlier studies have reported that chitosan films can be used for preservation of foods in packaging and reducing microbial numbers on health care (Hamed, Özogul, & Regenstein, 2016; Roller & Covill, 1999). The antifungal effect can be offered to the paper by the immobilization of CNFs on cellulose fibers before paper forming or by the incorporation into surface coating films. The positive charges in chitosan enhance the permeability of the membrane and leakage of cellular contents through interaction with negatively charged phospholipids of fungal membrane. The other mechanisms through which chitosan acts as antifungal agent are related to its binding to trace nutrients and inhibition of DNA synthesis (Kong, Chen, Xing, & Park, 2010; Rabea, Badawy, Steurbaut, & Stevens, 2009). Studies reported that chitosan based nanoparticles has antifungal activity in some fungi such as A. brassicicola, A. solani, A. flavus, A. niger and etc. (Kashyap, Xiang, & Heiden, 2015; Saharan et al., 2013). It has been reported that the chitosan nanofibers (CNFs) showed more effective antimicrobial activity compared with chitosan, may be due to their high surface to volume ratio and higher affinity with the cells, which produce a quantum-size effect (Jayakumar, Prabaharan, Nair, & Tamura, 2010).