Abstract. Rahayu HM, Putri WA, Khasanah AU, Sembiring L, Purwestri YA. 2021. Indigenous Streptomyces spp. isolated from Cyperus rotundus rhizosphere indicate high mercuric reductase activity as a potential bioremediation agent. Biodiversitas 22: 1519-1526. The purification and characterization of mercuric reductase of four indigenous Streptomyces spp. from Cyperus rotundus L. rhizosphere in mercury-contaminated area have been investigated. Cell-free extract was obtained by disrupting cells using sea sand at 4 °C followed by centrifugation. Mercuric reductase was purified by ammonium sulfate precipitation, dialysis, and chromatography column (DEAE Sepharose anion column chromatography). The determination of optimum pH and temperature of mercuric reductase activity was measured based on the number of NADPH2 oxidized to NADP per mg protein per minute using a spectrophotometer. The molecular weight of mercuric reductase was determined using SDS-PAGE. Result showed that the highest specific activity of mercuric reductase was recorded from Streptomyces spp. BR28. The optimum pH and temperature of cell-free extract enzyme mercuric reductase were 7.5 and 80 °C, respectively. The enzyme was purified to 431.87-fold with specific activity 21918.95 U/mg protein. SDS PAGE showed that the molecular weight of mercuric reductase in Streptomyces spp. BR 28  ranged from 50 kDa to 75 kDa. It can be concluded that Streptomyces isolates contain mercuric reductase and have potential as mercury bioremediation agent to overcome mercury contamination in the environment.

Efforts to control mercury pollution have been made for the last twenty years using various biological, physical, and chemical approaches. Streptomyces is able to degrade mercury because it possesses the mercuric reductase enzyme encoded by merA. The merA from Streptomyces isolate AS2 (Accession numbers LC026157) has been cloned into the expression vector pEt-28c(+). Therefore, it is critical to study recombinant mercuric reductase protein's expression and to analyse the protein structure. Expression of merA from an AS2 isolate was successfully performed in the host Escherichia coli BL21. Detection of mercuric reductase using SDS-PAGE showed a dominant band at 55–70 kDa. E. coli BL21 induction by IPTG was optimal at concentrations of 1 and 1.2 mM, and the optimal incubation times were 18 hours. The highest specific activity of mercuric reductase was 294.07 U/mg. Mercuric reductase protein in Streptomyces AS2 shares high homology with Lysinibacillus sphaericus (Swiss-Model), and similar folding to that of c5c1Yc refers to mercuric reductase from L. sphaericus using Phyre2. Based on amino acid sequences, the result revealed that Streptomyces AS2 strains were a group of Streptomyces lividans. These results give new insight to study further into a potential of MerA for bioremediation in the environment.

Tobacco leaf contains bioactive compounds as antibacterial. Staphylococcus aureus is a pathogenic bacteria causing several infection  diseases. The purpose of this study was to identify the active compounds group that have antibacterial against and determine the optimum  concentration which was able to inhibit S.aureus ATCC 25923 activity in tobacco leaf extract. The assay of inhibitory activity of tobacco leaf extract was carried out qualitatively using diffusion disc method at various concentration of tobacco leaf extract; 40, 50, 60, 70, 80, 90, and 100%. Gradual maceration (M2) and total maceration were used to perform the extraction process, using methanol 70% and etanol 96% as the solvent. Thin Layer Chromatografi (TLC) assay were carried out to identify the bioactive compounds. The results showed that the methanol (M2) and etanol (E) extract of tobacco leaf had antibacterial avtivity against S.aureus. Their bactericidal activity (inner diameter of inhibition) was 12,5 mm, and bacteriostatic (outer diameter inhibition) was 20 mm. The optimum concentration of antibacterial methanol extract was 50%, and the optimum concentration of antibacterial etanol extract was 60%. It was found that the antibacterial compound was detected as flavonoid and terpenoid.

Abstrak Produk yang sudah tersertifikasi halal dapat beredar di berbagai wilayah di Indonesia. Saat ini, proses pengajuan sertifikasi halal, dilayani di LPPOM MUI. Bahan baku yang digunakan oleh produsen menjadi bagian dari keharusan untuk didaftarkan dalam borang matrix bahan baku tanpa terkecuali. Bidang audit mengusulkan kepada komisi fatwa berupa sekumpulan hasil borang audit yang telah lolos dalam rapat post audit. Tujuan penelitian ini adalah melihat tingkat penggunaan bahan tersertifikasi halal dan asal produk dari perusahaan yang mengajukan sertifikasi halal di Banten selama tahun 2017. Penelitian ini menggunakan metode studi pustaka terhadap bahan dari tiap produsen yang diusulkan oleh bidang audit LPPOM MUI Banten kepada komisi Fatwa MUI di tahun 2017. Hasil penelitian menunjukkan bahwa  asal sertifikasi halal  yang digunakan oleh sebagian besar produsen di Provinsi Banten secara berturut-turut berasal dari LPPOM Pusat 75,78%; LPPOM Banten 7,08%; LPPOM Jawa Barat 5,21%; LPPOM Jawa Timur 4,70%; LPPOM DKI 2,22%. Produsen di Banten, sebagian besar menggunakan kelompok Roti dan Kue (bakery) 37,97%; kelompok makanan ringan (snack) 17,62%; kelompok daging dan produk daging olahan 11,56%; kelompok restorant 8,92% dan kelompok katering 6,57%. Semakin tinggi rangking kelompok produk yang digunakan oleh produsen, maka semakin tinggi frekuensi produk ditemukan oleh auditor LPPOM MUI Banten.. Kata kunci: sertifikasi halal, bisang audit, komisi fatwa, LPPOM, MUI

Streptomyces is one of mercury‐resistant bacteria which can convert Hg2+ into nontoxic Hg0 . This study aimed to identify mercury‐resistant Streptomyces present in the Cyperus rotundus rhizosphere from artisanal small‐scale gold mining (ASGM) area and clone merA gene to the cloning and expression vectors. Molecular identification was conducted using 16s rRNA gene with the maximum likelihood algorithms. Results revealed that the AS1 and AS2 strains were a group of Streptomyces ardesiacus and the BR28 strain was closed to Brevibacillus agri. The AS2 merA gene was cloned to pMD20 cloning vectors, pGEX‐5x‐1 and pET‐28c expression vectors. The transformation was successfully performed in BL21 and DH5α competent cells. The full length of the merA gene was confirmed to be 1,425 bp. This study is the first research on identifying mercury‐resistant Streptomyces and cloning the full‐length merA gene in Indonesia.