不同分子量澳洲坚果多肽氨基酸组成与抑菌活性

以液压压榨澳洲坚果粕为原料，采用碱性蛋白酶水解制备多肽（MNP-0），通过分级透析将其分离为8种不同分子量的澳洲坚果多肽（MNP-1、MNP-2、MNP-3、MNP-4、MNP-5、MNP-6、MNP-7、MNP-8）组分，测定其多肽含量、氨基酸组成与抑菌活性。结果表明:不同分子量澳洲坚果多肽呈现不同的质量占比，氨基酸组成也有所差异。其中，澳洲坚果多肽MNP-8占比最高，为25.09%，其所含有的与抗菌作用有关的丙氨酸、缬氨酸、亮氨酸、脯氨酸及总疏水性氨基酸占比最高，分别为3.38%、2.42%、4.67%、4.39%与26.92%。多肽MNP-6占比也较高，为18.52%，与多肽MNP-4无显著性差异（P>0.05），其所含有的与抗菌作用有关的赖氨酸占比最高，为6.03%。不同分子量澳洲坚果多肽抑菌效果也不尽相同，其对金黄色葡萄球菌、鼠伤寒沙门氏菌、大肠埃希氏菌、铜绿假单胞菌抑菌活性较好，对白色念珠菌与黑曲霉相对较差。其中，澳洲坚果多肽MNP-8对金黄色葡萄球菌、鼠伤寒沙门氏菌、大肠埃希氏菌、铜绿假单胞菌、白色念珠菌抑菌活性最好，在4 mg/mL浓度下，其抑菌圈直径分别为15.92、14.67、13.70、16.98、12.47 mm，最低抑菌浓度（MIC）分别为4.0、5.0、4.5、3.5、18.0 mg/mL。不同分子量澳洲坚果多肽的抑菌活性与其分子量及氨基酸组成密切相关。

Amino Acid Compositions and Antibacterial Activities of Different Molecular Weight Macadamia Nut Polypeptides

Macadamia nut polypeptides was prepared by the alkali protease hydrolysis.Eight constituents(MNP-1,MNP-2,MNP-3,MNP-4,MNP-5,MNP-6,MNP-7,MNP-8)were obtained by dialysis technology,its peptides contents,amino acid compositions and antibacterial activities were analyzed.Results showed that the quality proportions and amino acid compositions of different molecular weight Macadamia nut polypeptides were different.Macadamia nut polypeptide MNP-8 had the highest proportions,which was 25.09%,its alanine,valine,leucine,proline and total hydrophobic amino acids related to antimicrobial activity had the hightest proportion,which were 3.38%,2.42%,4.67%,4.39%and 26.92%,respectively.The polypeptide MNP-6 had the higher proportions,which was 18.52%,and was no significant difference with the polypeptide MNP-4(P>0.05),its lysinerelated to antimicrobial activity had the hightest proportion,which was 6.03%.The antibacterial activities of different molecular weight Macadamia nut polypeptides were also different,which had the better antibacterial activities on the Staphylococcus aureuss,Salmonella typhimurium,Escherichia coli and Pseudomonas aeruginosa,and the worse antibacterial activities on the Candida albicans and Aspergillus niger.Macadamia nut polypeptide MNP-8 had the best antibacterial activities on the Staphylococcus aureuss,Salmonella typhimurium,Escherichia coli,Pseudomonas aeruginosa and Candida albicans,its diameter of bacteriostatic zones were 15.92,14.67,13.70,16.98,respectively,and 12.47 mm at a concentration of 4 mg/mL,and the MIC were 4.0,5.0,4.5,3.5 and 18.0 mg/mL,respectively.The antibacterial activities of different molecular weight Macadamia nut polypeptides were closely related to their molecular weigh tand amino acid compositions.This study provided the references for the development and utilization of the antibacterial activities of Macadamia nut polypeptides.