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: 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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