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In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 13 PleaseRSC do not Advances adjust margins RSC Advances ARTICLE Changes to amino acid composition of bloodmeal after chemical oxidation Received 00th January 20xx, a a a b Accepted 00th January 20xx T. M. Hicks, C. J. R. Verbeek, M. C. Lay, and M. Manley-Harris DOI: 10.1039/x0xx00000x Bovine-derived bloodmeal can be decoloured using peracetic acid, extruded and injection moulded into a yellow translucent bioplastic. This plastic has different properties to extruded and injection moulded bloodmeal, in that it does www.rsc.org/ not require sodium sulfite or urea to be extrudable. The effect of oxidation on the physical and chemical characteristics of the proteins during bloodmeal decolouring with PAA was studied by assessing changes in the amino acid profile. Polymer interactions, hydrophilicity and the destruction of cysteine crosslinks were measured indirectly by assessing protein Manuscript solubility, molecular weight distribution and by synchrotron FT-IR analysis. Increasing peracetic acid concentration resulted in an increased loss of iron due to destruction of the porphyrin groups, increased solubility due to destruction or conversion of aromatic amino acids into hydrophilic groups, destruction of lysine, reduced protein content due to increased salt content in the final product, and a larger amount of smaller protein peptides but with a similar average molecular weight to bloodmeal. Amino acid analysis showed an increase in cysteine content in the product, FTIR of the sulfur groups revealed that these were heavily oxidised, such that some would be unable to participate in disulfide bonds thereby increasing protein solubility. performing a specific function in the overall decolouring and Introduction deodorising mechanisms.10 The presence of several reactive species and the formation of A semi-transparent bioplastic has been produced from free radicals, resulted in oxidative damage to the proteins as bloodmeal by decolouring it using commercial peracetic acid 11 1-3 the radicals underwent auto-reduction reactions. (PAA) followed by extrusion. Decolouring bloodmeal using 3 Consequently, treating proteins with oxidising agents leads to – 5 wt% PAA has been found to result in the lowering of the o o 2 undesired side effects, including modification of amino acid glass transition temperature from ~225 C to ~35 – 45 C and residues, protein hydrolysis or chain cleavage and protein also to require different processing aids for extrusion. In Accepted aggregation.7, 12 The type of damage and the extent of contrast to thermoplastic prepared from untreated bloodmeal, modification varied depending on the reduction potential and once decoloured, bloodmeal no longer required sodium sulfite 2 concentration of the oxidant, as well as the presence of other reduction of the cysteine crosslinks in order to be extruded. species which exhibited anti-oxidant or free radical scavenging Peracetic acid, which is an equilibrium mixture of peracetic properties. acid, hydrogen peroxide and acetic acid, has been used Bleaching wool with performic or peracetic acid selectively extensively since the early 1940s due to growing concerns over oxidised cystine (disulfide crosslinks), methionine and the environmental impact of chlorine. It is used as a bleaching 4-7 tryptophan side chains with minimal significant degradation of agent for textiles, as a disinfectant, as well as in wastewater the other amino-acids.13 However, a later study indicated that treatment. It does not form harmful disinfection by-products performic acid also degraded serine, threonine, tyrosine, and decomposes safely when discharged into the 8, 9 phenylalanine and histidine, while PAA oxidation resulted in environment. the conversion of all cystine to cysteic acid, with only small Common oxidants such as hydrogen peroxide are unable to losses of tyrosine, phenylalanine and histidine.14 Oxidation of degrade all of the haem present in bloodmeal due to the 3, 10 cystine bonds also occurs during hydrogen peroxide bleaching various oxidation states of haem-iron in haemoglobin. of human hair (keratin is highly crosslinked as a result of However, peracetic acid adequately removed the colour from disulfide bonds between cysteine residues). As a result, bloodmeal, with each component of the PAA solution Advances oxidation of hair and wool by hydrogen peroxide or peracetic acid led to a loss in tensile strength proportional to the 15-17 a. number of cystine residues degraded. Oxidation of bovine School of Engineering b. serum albumin and aldolase proteins with PAA was found to School of Science 18 Faculty of Science and Engineering, University of Waikato, Private Bag 3105, induce chain fragmentation. Hamilton 3240, New Zealand Oxidation of amino acids in proteins is dependent on oxidant † Footnotes relating to the title and/or authors should appear here. Electronic Supplementary Information (ESI) available: [details of any strength, concentration, pH and a range of other chemical supplementary information available should be included here]. See RSC This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 1 Please do not adjust margins PleaseRSC do not Advances adjust margins Page 2 of 13 ARTICLE Journal Name conditions. The most recent investigation into the effect of This paper describes the effect of oxidation during bloodmeal PAA oxidation on dairy proteins, indicated that the amount of decolouring using PAA on the physical and chemical carbonyl groups increased while thiol (SH) groups decreased; characteristics of the proteins manifested by changes in the tryptophan and methionine were most vulnerable to oxidation amino acid profile. Polymer interactions and hydrophilicity while lysine was not affected.7 Neither peptide cleavage, nor were measured indirectly by assessing protein solubility and protein aggregation occurred to any significant extent.7 This is molecular weight distribution, while the destruction of probably as a result of the protective effect of short chain cysteine crosslinks was measured via synchrotron FT-IR carboxylic acids (or their salts) on proteins exposed to analysis. 23, 34-36 hydrogen peroxide, which has been attributed to their action as chelating agents (inhibiting Fenton-type reactions) or as scavengers of reactive oxygen species and free radicals;19, 20 Experimental both of the latter cause protein hydrolysis. This concurs with Materials peracetic acid decolouring of bloodmeal, in which the presence of acetic acid (or sulfuric acid) inhibited the reactivity Bovine bloodmeal was obtained from Wallace Corporation Ltd, of hydrogen peroxide.10 New Zealand and sieved to utilise particles under 710 µm. Helices, sheets, turns and coils which define the secondary Peracetic acid, an equilibrium mixture of peracetic acid, structure of the protein are modified by oxidation.21, 22 Amino hydrogen peroxide, acetic acid and water (Proxitane Sanitizer acids show a propensity to form particular types of secondary 5%) was purchased from Solvay Interox Pty Ltd Auckland, New structures, with most amino acids showing preference for only Zealand and diluted with distilled water to the appropriate Manuscript one type (Table 1),23 although, the periodicity and positioning concentration for decolouring (Table 2). Hydrogen peroxide of polar and non-polar residues in the amino acid sequence is (30 wt% EMSURE, ISO) was purchased from Merck, Auckland, known to have a greater influence on a peptide’s final New Zealand. Analytical grade glacial acetic acid, sodium secondary structure.24 Selective oxidation of certain amino hydroxide, sodium dodecyl sulfate, sodium chloride, acids may influence the formation of specific secondary monosodium phosphate and disodium phosphate were structures by changing the ability to form H bonds between purchased from ThermoFisher Scientific, Auckland, New C=O and NH groups. Zealand. The sensitivity of particular amino acid residues to oxidation by Bloodmeal Decolouring oxidants has been shown to vary between proteins and results from their position and interaction within the protein Bloodmeal was decoloured by adding 450 g of a 1 – 5 wt% structure.25 peracetic acid solution, or 26 wt% hydrogen peroxide (with or Oxidation of amino acids has been shown to cause increases in without 6.6 wt% acetic acid) to 150 g bloodmeal and reacting local flexibility or rigidity in the protein chain, leading to an the mixture under constant agitation for 10 min in a Kenwood 37 alteration in its secondary structure,21,