Judul: Produksi dan Karakterisasi Senyawa Inhibitor alfa-Glukosidase Streptomyces sp. BWA
Abstrak: Endophitic Streptomyces sp. BWA 65 from brotowali (Tinospora crispa) produces α-glucosidase inhibitor compound that acts as antidiabetic. This study aimed to produce and characterize α-glucosidase inhibitory compound of Streptomyces sp. BWA 65 and assay its biological function as antidiabetic based on α-glucosidase inhibitory activity. Streptomyces sp. BWA 65 which was rejuvenated in Yeast Soluble Starch Agar (YSA) for 7 until 10 days, was then cultured in a liquid medium for 7 days, and produced in International Streptomyces Project-2 (ISP-2) for: 5, 10, 15, and 20 days. Then, supernatant was extracted with ethyl acetate and was assayed for α-glucosidase inhibition activity. The ethyl acetate extract of Streptomyces sp. BWA 65 was also assayed for its Inhibitor Concentration 50 (IC50) value. The characteristics of α-glucosidase inhibitor profile compounds which contained in the ethyl acetate extract was analyzed by Gas Chromatography–Mass Spectroscopy (GC-MS). The results showed that the highest α-glucosidase inhibitor activity was 98.50% when the Streptomyces sp. BWA 65 was grown on ISP-2 10 days production time. The IC50 of ethyl acetate extract of Streptomyces sp. BWA 65 was 0.047 μg ml-1. The results of GC-MS analysis were interpreted with OPCWTEST.M database showed that the ethyl acetate extract of Streptomyces sp. BWA 65 contained 7 peaks with 7 components obtained. The chemical components of ethyl acetate extract of Streptomyces sp. BWA 65, were: 9-octadecenoic acid, (E)-, oleic acid, dan 6-octadecenoic acid, (Z)-.
Keyword: Bogor Agricultural University (IPB), Streptomyces sp. BWA 65, GC-MS, IC50, α-glukosidase inhibitor

Judul: Aktivitas Inhibitor Alpha Glukosidase Streptomyces sp. BWA 65 pada beberapa Media, pH, dan Suhu
Abstrak: Streptomyces sp. BWA 65 is a genus of actinomycetes from brotowali (Tinospora crispa), which produces α-glucosidase inhibitor as antidiabetic. Production of this compound is influenced by external factors such as media, pH, and temperature. The α-glucosidase inhibitor activity was assessed at various media, pH, and temperature. Streptomyces sp. BWA 65 grew and sporulated well on YSA medium, indicated by the formation of white colonies after incubation for 7-10 days. ISP-2 medium was the best growth medium compared with YS and ISP-4 media. In this ISP-2 medium, Streptomyces sp. BWA 65 produced optimum inhibition of it’s supernatant and it’s ethyl acetate extract after 10 days of production time. This optimum growth condition was used for the production of α-glucosidase inhibitor compound using a fermentor at control condition, e.g. 27- 29 °C, pH 7, and oxygen pressure at 3-5 mmHg. The α-glucosidase inhibitor compound produced was assayed at various pH and temperature. The higest percentage of inhibitor activity of supernatant and ethyl acetate extract was found at pH 7, 27 °C for 24 h incubation. At this condition, the highest percentage of inhibition of the supernatant was 90.2 %, while for ethyl acetate extract was 91.8 %. As a comparison, acarbose at 1000 ppm concentration gave 98,6 % inhibition activity.
Keyword: Bogor Agricultural University (IPB), temperature, Streptomyces sp. BWA 65, pH, medium, α-glukosidase inhibitor activity

Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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