Judul: Purification and Characterization Sericin Protein Cocoon of Eri (Samia cynthia ricini) silkworm
Abstrak: Protein serisin merupakan perekat antar serat (fibril). Protein serisin diekstraksi dari limbah air degumming serat sutra. Serisin Samia cynthia ricini didapatkan dengan melakukan degumming menggunakan NaOH 0,033N dengan kombinasi suhu dan waktu 113 oC selama 34 menit. Hasil crude protein serisin kemudian dipurifikasi dengan netralisasi menggunakan HCL serta presipitasi etanol. Hasil purifikasi dikarakterisasi berat molekulnya menggunakan sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) dan didapatkan hasil berat molekul serisin sebesar 7,08 kDa. Asam amino serisin S. ricini dikarakterisasi menggunakan high performance liquid chromatography (HPLC) dan dihasilkan asam amino tertinggi pada glisina (15,35%). Aktivitas dalam penghambatan DPPH diketahui sebesar 66,86% dengan kapasitas antioksidan 8,03 mg VCE mL-1. Sifat antibakteri dimiliki serisin S. ricini terhadap bakteri S. aureus dengan zona hambat 6,74 mm dan persentase penurunan kekeruhan 80.04%., Sericin is a protein that acts as an adhesive joining two fibroin filaments. Sericin protein was extracted from silk wastewater. Silk wastewater was produced from degumming of cocoon Samia cynthia ricini with NaOH 0,033N and a combination of temperature and time 113 oC for 34 minutes. Crude sericin protein was purified with neutralization of HCL and ethanol precipitation. The molecular weight of purified protein was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and the results of S. ricinisericin molecular weight is 7,08 kDa. The amino acid of S. ricini sericin was investigated by high performance liquid chromatography (HPLC) that result in highest component is glycine (15,35%). Sericin S. ricini has 66,86% antioxidant activity with 8,03 mg VCE mL-1 antioxidant capacity. Antibacterial attribute of sericin S. ricini inhibit toward S. aureus bacteria with 6,74 mm inhibition zone and 80,04% in turbidity decrease percentage.
Keyword: purification, Samia cynthia ricini, sericin, SDS-PAGE, HPLC

Judul: Characteristic Sericin Protein Cocoon of Eri  (Samia cynthia ricini) using Different NaOH Solvent Concentrations
Abstrak: Serisin merupakan protein globular penyusun kokon ulat sutra yang memiliki beragam manfaat di bidang pangan, kosmetik, farmasi, dan biomedis. Pada penelitian sebelumnya, rendemen serisin yang diperoleh menggunakan larutan degumming NaOH 0,1 N belum optimal. Penelitian ini bertujuan menganalisis rendemen protein, bobot molekul, dan susunan asam amino protein serisin kokon ulat sutra Eri dengan larutan degumming NaOH 0,25 N. Hasil ekstraksi protein serisin dengan larutan degumming NaOH 0,25 N menghasilkan rendemen serisin sebesar 23,6±4,1%. Hasil tersebut lebih baik dibandingkan bila menggunakan larutan degumming NaOH 0,1 N (4,8±1,5%). Bobot molekul protein serisin hasil isolasi memiliki rentang bobot molekul protein 15,68-45,70 kDa yang sesuai dengan kisaran bobot molekul serisin dari literatur. Hasil analisis HPLC menunjukan bahwa komponen asam amino utama protein serisin adalah alanina, glisina, dan tirosina., Sericin is a globular protein forming silkworm coccon that have various function in foods, cosmetics, pharmaceuticals, and biomedical industry. Previous research have used 0.1 N NaOH degumming solvent and considered not optimal in producing yields. This research purpose to analyze the protein yield, molecular weight, and amino acid composition of the Eri silkworm cocoon sericin protein using 0.25 N NaOH degumming solvent. The results of protein sericin extraction with 0,25 N NaOH degumming solvent resulted sericin yield of 23.6%±4,1. These result is better than using NaOH 0.1 N degumming solvent (4,80%±1,51). The molecular weight of isolation sericin protein is 15.68-45.70 kDa which corresponds to the range of molecular weights from the literature. The result of the HPLC analysis showed that the main amino acid components of the sericin protein is alanine, glisine, and tyrosine.
Keyword: Eri Silkworm Cocoon, NaOH, Solvent, Samia cynthia ricini, Sericin

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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