Protein kacang kedelai (Glycine max (L.)) sebagai protein berbasis tumbuhan menawarkan kelebihan dalam aspek lingkungan, etika, maupun sosial dibandingkan protein hewani. Protein kacang kedelai lebih banyak diekstraksi menggunakan metode ekstraksi protein konvensional oleh berbagai industri karena dianggap lebih ekonomis. Namun, ekstraksi protein dengan metode konvensional masih memiliki keterbatasan, yaitu tingginya potensi pengotor seperti metabolit sekunder ikut terlarut dalam rendemen protein. Untuk mengatasi hal tersebut, presipitasi protein dengan pelarut organik berupa aseton dipilih sebagai solusi karena memiliki keunggulan, yaitu cepat, murah, dan minim menyebabkan degradasi sehingga dapat menghasilkan nilai recovery yang tinggi. Penelitian ini bertujuan untuk mengetahui pengaruh metode presipitasi protein terhadap rendemen ekstraksi dan kemurnian protein dari kacang kedelai. Adapun, tujuan tersebut dicapai dengan menganalisis profil protein dengan metode SDS-PAGE, kadar protein dengan metode BCA Assay, serta kadar metabolit sekunder isoflavon pada ekstrak dengan presipitasi protein dan ekstrak tanpa presipitasi protein dengan menggunakan metode KLT-densitometri.
Persentase jumlah protein dalam pelet pada sampel dengan penambahan tahap presipitasi protein dengan aseton lebih rendah dibanding sampel tanpa penambahan presipitasi protein dengan aseton. Rasio sampel-aseton 1:2 (v/v) menjadi rasio sampel-aseton terbaik karena mampu menghasilkan persentase jumlah protein dalam pelet tertinggi, yaitu sebesar 35,256% (b/b). Selain itu, rasio ini juga dapat dipilih apabila beta-conglycinin alfa subunit atau alfa' subunit dan glycinin basic subunit menjadi protein target. Sementara itu, apabila jumlah aseton menjadi parameter yang dipertimbangkan dan beta-conglycinin alfa subunit atau alfa' subunit serta glycinin basic subunit bukan termasuk protein yang ditagetkan, maka rasio sampel-aseton 1:1 (v/v) dapat menjadi pilihan. Profil protein pada kacang kedelai yang terdeteksi berupa beta-conglycinin alfa subunit atau alfa' subunit, beta-conglycinin beta subunit, glycinin acidic subunit, glycinin basic subunit, probable phytol kinase, eukaryotic translation initiation factor 4E-1, nodulin-26B, CASP-like protein 2A1, nucleoside diphosphate kinase 1, protein early responsive to dehydration 15, dan albumin-1. Penambahan metode presipitasi protein dengan aseton mampu menghilangkan metabolit sekunder isoflavon genistein sehingga dapat diperoleh ekstrak protein yang lebih murni.
Soybean protein (Glycine max (L.)) as a plant-based protein offers environmental, ethical, and social advantages compared to animal protein. Soybean protein is often extracted using conventional methods by various industries due to its perceived economic benefits. However, conventional protein extraction still has limitations, including the high potential for impurities, such as secondary metabolites, to be dissolved in the protein yield. To address this issue, protein precipitation with organic solvent such as acetone was chosen as a solution due to its advantages: speed, cost, and, minimal degradation, resulting in high recovery rates. This research aimed to determine the effect of protein precipitation with acetone on the extraction yield and purity of soybean protein. The objective was achieved by analyzing protein content using BCA Assay, the protein profile using SDS-PAGE, the protein purity as seen from the presence of the secondary metabolite isoflavone genistein using TLC-densitometry.
The percentage of protein in the pellet of the samples with the addition of the protein precipitation step with acetone was lower than in sample without it. The sample-acetone ratio of 1:2 (v/v) was identified as the optimal sample-acetone ratio as it produced the highest average protein percentage in the pellet, reaching 35,256% w/w. Furthermore, this ratio may be preferred when targeting the beta-conglycinin alfa subunit or alfa' subunit and glycinin basic subunit. Conversely, when minimizing acetone usage is prioritized and these target proteins are not the primary interest, a sample-acetone ratio of 1:1 (v/v) may serve as suitable alternative. The soybean protein profile identified in this study consisted of the beta-conglycinin alfa subunit or alfa' subunit, beta-conglycinin beta subunit, glycinin acidic subunit, glycinin basic subunit, probable phytol kinase, eukaryotic translation initiation factor 4E-1, nodulin-26B, CASP-like protein 2A1, nucleoside diphosphate kinase 1, protein early responsive to dehydration 15, and albumin-1. In addition, the incorporation of the protein precipitation method with acetone effectively removed the secondary metabolite of isoflavone genistein, thereby yielding a purer protein extract.
Kata Kunci :
Kacang kedelai, kemurnian protein, presipitasi protein, protein, rendemen ekstraksi protein.
