Occurrence of qualitative and quantitative polymorphism at donkey beta-Lactoglobulin II locus Lina Chianese a, ⁎, Carmela De Simone a , Pasquale Ferranti a , Rosalba Mauriello a , Angela Costanzo a , Maria Quarto a , Giuseppina Garro a , Gianluca Picariello b , Gianfranco Mamone b , Luigi Ramunno c a University of Naples Federico II, Department of Food Science, Parco Gussone, CAP 80055, Portici, Naples, Italy b National Research Council, Institute of Food Sciences, Via Roma 52 A/C, CAP 83100, Avellino, Italy c University of Naples Federico II, Department of Soil, Plant, Environmental and Animal Productions Sciences, Parco Gussone, CAP 80055, Portici, Naples, Italy abstract article info Article history: Received 10 September 2012 Accepted 5 November 2012 Keywords: Donkey milk whey proteins Proteomics Genetic polymorphism Beta-lactoglobulin With the use of a proteomic approach a genetic screening of 70 individual donkey milk samples, from two autochthonous breeds reared in Italy, was carried out to determine the genetic polymorphism at donkey β-Lgs loci. The achieved results showed the occurrence of the new β-Lg II E genetic variant, differing from β-Lg II D reference for D Asp 2 /E Asn 2 , D Arg 18 /E Lys 18 and D Val 25 /E Ala 25 amino acid substitutions with a M r 18 256 Da. Moreover a quantitative polymorphism seemed to affect the donkey β-Lg II locus since four phenotypes, with a relative quantitative percentage respect to total whey protein ranging from 0% to 3.65%, were detected by HPLC analysis. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction The increased incidence of allergies and/or intolerances to bovine milk in newborns enhanced the production of infant formulae based on either bovine or soy proteins hydrolysates. However, peptides with a molecular size able to trigger an immune response in predisposed subjects can survive the production process and soy hy- drolysates seem to cause a negative sensorial acceptance in infant consumers (Businco et al., 2000; Muraro, Giampietro, & Galli, 2002). Basically, allergies and/or intolerances to bovine milk are mainly depending on milk proteins otherwise present at very lower amount (α s1 -CN) or not expressed (α s2 -CN and β-Lg) in human milk (Docena, Fernandez, Chirdo, & Fossati, 1996). To this aim, the milk from mammalian species having a more similar composition to human milk could be usefully employed. The sensitization to cow allergy, measured as anti-goat β-Lg antibodies, was found significantly de- creased in guinea pigs fed on goat milk containing traces of α s1 -CN (Bevilacqua et al., 2001). Nevertheless, the availability of these types of milk requires a genetic screening to select the animals carrying weak or null alleles at α s1 -CN locus. On the contrary, due to natural similarity to human milk, the positive effects of donkey milk in nutri- tion of cow's milk protein allergy infants have been reported (Monti et al., 2007). In addition to in vivo beneficial healthy effects, important bioactivities of donkey milk were found by in vitro assays, such as a potent cytotoxicity causing tumor cell death by apoptosis (Mao et al., 2009) and an inhibitory effect against several bacterial species in vitro (Tidona et al., 2011; Zhang, Zhao, Jiang, Dong, & Ren, 2008). These effects were positively related to the higher level of lysozyme (Lyz) (Salimei et al., 2004) in donkey milk than in cow counterpart (Guo et al., 2007; Vincenzetti et al., 2008). To date, the composition of donkey milk in terms of TN (total nitrogen), CN (casein nitrogen), WPN (whey protein nitrogen), NPN (non protein nitrogen) and lactose content, as well as of CN/WPN ratio, has been the “scientific rationale” of its close similarity to human counterpart (Guo et al., 2007). Even though the quantitative level of TN is lower than cow milk (1.5–1.8% vs 3.1–3.8%), the WPN amount in both milks is very similar (0.49–0.80% vs 0.55–0.70%) (Guo et al., 2007). From a qualitative point of view, very recently, the four casein fractions, α s1 , α s2 , β and κ-CN were found constitutive of asinine CN (Chianese et al., 2010). Each of them showed a high compositional heterogeneity due to concomitant presence of deleted non allelic forms and discrete phosphorylation (α s1 , α s2 , β-CN) or glycosylation (κ-CN) degree as in goat and sheep milks (Ferranti et al., 1997; Ferranti, Lilla, Chianese, & Addeo, 1999). More scientific data were available on donkey whey proteins (WPs), consisting of α-La, β-Lg, blood serum albumin (BSA), lactoferrin (Lf) and Lyz as in ruminants (Martin, Szymanowska, Zwierzchowski, & Leroux, 2002) and horse milk (Uniacke-Lowe, Huppertz, & Fox, 2010). The primary structures of donkey WPs, as expected, showed a higher identity with horse than bovine counter- parts. Donkey β-Lg, for instance, was consisting of two components, the major β-Lg I and the minor β-Lg II; the former is 162 a.a. residues Food Research International 54 (2013) 1273–1279 ⁎ Corresponding author. Tel.: +39 081 2539011; fax: +39 081 7762580. E-mail address: chianese@unina.it (L. Chianese). 0963-9969/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodres.2012.11.005 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres