Judul: Optimization of Silkworm Sericin Yield Samia cynthia ricini in Degumming Process Using Response Surface Methodology
Abstrak: Serisin ulat sutra eri (Samia cynthia ricini) merupakan produk samping pengolahan serat sutra yang memiliki berbagai manfaat. Formulasi degumming yang tepat diperlukan untuk mencapai rendemen serisin optimum, dipengaruhi oleh suhu, waktu, dan konsentrasi larutan degumming yang menjadi variabel bebas dalam penelitian ini. Penelitian ini bertujuan memperoleh formulasi degumming yang menghasilkan rendemen serisin optimum serta menganalisis karakteristiknya. Metode yang digunakan yaitu Response Surface Methodology (RSM) dengan titik pusat pada konsentrasi larutan degumming Na2CO3 0,02 N, suhu degumming 70 °C selama 30 menit yang dirancang dengan Central Composite Design (CCD). Kondisi optimum dicapai pada proses degumming menggunakan konsentrasi larutan degumming Na2CO3 0,026 N pada suhu 74 °C selama 30 menit dengan perolehan rendemen serisin sebesar 20,21±0,35%. Serisin pada kondisi optimum degumming memiliki berat molekul 51 hingga 83 kDa dengan persentase susunan asam amino terbesar adalah asam amino polar. Hasil yang diperoleh telah sesuai dan mencerminkan sifat protein serisin., The sericin of the eri silkworm (Samia cynthia ricini) is a by-product of fiber processing that can be used in various fields. The study aimed to optimize the degumming conditions for sericin from eri silkworm, emphasizing temperature, time, and solution concentration as independent variables. Response surface methodology (RSM) was employed with initial conditions at 0,02 N Na2CO3 degumming solution, 70 °C and 30 minutes, using a central composite design (CCD). Optimal conditions were determined as 0,026 N Na2CO3, 74 °C for 30 minutes with the yield recorded was 20,21±0,35%. Analysis at these conditions revealed sericin with a molecular weight of 51 to 83 kDa, predominantly composed of polar amino acids
Keyword: ulat sutra, Samia cynthia ricini, response surface methodology, Degumming, Serisin

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: 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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