Judul: Pengaruh Umur Kertas dan Penggunaan Bahan Kolektor terhadap Penghilangan Tinta Kertas Koran Bekas
Abstrak: Kertas bekas merupakan salah satu alternatif potensial sebagai sumber serat sekunder untuk digunakan sebagai bahan baku kertas. Penyedian kayu sebagai sumber pulp murni untuk dijadikan kertas pada saat ini mendapat berbagai masalah, baik dari segi biaya proses pengolahan maupun penyediaan kayu.
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Judul: Pemanfaatan kertas koran bekas sebagai bahan baku dalam pembuatan kertas karton
Abstrak: Meningkatnya konsumsi domestik pulp dan kertas dan makin terbatasnya sumber bahan baku konvensiaonal (kayu) menimbulkan pemikiran pencarian bahan baku alternatif. Salah satu usaha yang dapat dipertimbangkan adalah pemanfaatan kembali atau pendaur ulangan kertas koran bekas sebagai bahan baku. Disamping kertas koran bekas, sumber lain yang dapat dipertimbangkan adalah limbah padat berkadar air tinggi dari industri pulp dan kertas (sludge) yang selama ini hanya dibuang sebagai bahan pencampur. Campuran kertas koran bekas dan sludge antara lain dapat digunakan untuk pembuatan kertas karton. Penelitian ini bertujuan untuk mengetahui kualitas kertas karton dari kertas koran bekas dan sludge pada berbagai kombinasi campuran. Perlakuan yang diberikan adalah pencampuran pulp daur ulang kertas koran dengan sludge pada perbandingan 100:0; 90:10; 80:20; 70:30 (dalam persen berdasarkan berat kering tanur), dengan tiga ulangan. Lembaran dibuat dengan gramatur target 125gr/m². Parameter yang dianalisa adalah sifat fisik dan optik lembaran yang meliputi dimensi serat, rendemen, indeks sobek, indeks tarik, kekakuan, nilai ring crush, nilai concora, derajat putih dan opasitas. Rendemen serat yang terdapat di dalam sludge adalah 31,20 persen dan rendemen daur ulang kertas koran 84,36 persen. Panjang serat sludge berkisar 181,25μm-3000µm dengan rata-rata 862,78µm dan didominasi oleh serat terpotong atau tidak utuh. Panjang serat pulp koran bekas berkisar 300µm- 1305µm dengan rata-rata 852,50µm dan tebal dinding sel rata-rata 4,21µm dengan lumen rata-rata 8,65µm. ...
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Judul: Extracellular Expression of thermostable Geobacillus stearothermophilus T1.2RQ Lipase for Biodiesel Production
Abstrak: The extracellular expression of enzymes in an excellent secretion host such as Bacillus subtilis is a useful strategy for making enzymes of industrial significance more affordable by lowering the cost of its downstream processing. Lipases are a category of hydrolases that catalyze the hydrolysis of triglycerides to glycerol and free fatty acids. Also, lipases catalyze the hydrolysis and transesterification of other esters as well as the synthesis of esters. They can perform very specific biotransformation reactions and are widely used in food, organic synthesis, detergents, cosmetic, and pharmaceutical industries. Geobacillus stearothermophilus T1.2RQ lipase is an industrially-desired thermostable lipolytic enzyme with an excellent hydrolytic and transesterification activity. This study aimed to express T1.2RQ lipase, in B. subtilis WB800 and ensure its secretion into the extracellular medium. Three signal peptides (AmyQ, Epr, LipA) and two promoters (Pgrac01 and Pgrac100) were used in the secretory-expression of T1.2RQ lipase, based on five constructed expression vectors constructed by restriction cloning and PCR mutagenesis. Sangers sequencing was used to verify constructs to ensure they are in the correct reading frame. Recombinants vectors, pHT43 (plasmid control), pHT43-T1.2RQ, pHT43- T1.2RQ_AmyQ, pHT43-T1.2RQ_Epr, and pHT43-T1.2RQ_LipA, were transformed by electroporation into Bacillus subtilis WB800. The electroporation was successful with the optimum condition of 2500V, 200 ohms, 25µF, and 5milliseconds. Recombinant B. subtilis pHT43 (negative control) and pHT43-T1.2RQlip + signal peptides were streaked on the lipidic agar, LA+TBN. All four recombinants, including the negative control (B. subtilis WB800-pHT43), produced clear zones on the TBN agar plate after overnight incubation (fig 2), indicating the presence of a lipolytic enzyme in all of the recombinant B. subtilis cells. pHT43-T1.2RQlip + signal peptides (AmyQ, Epr, and LipA) have clear zones with significantly higher diameters than B. subtilis WB800-pHT43 (negative control). This phenomenon suggests that the recombinant thermostable lipase T1.2RQ introduced into these cells was successfully expressed, thereby increasing the lipolytic capability of its host cells T1.2RQ lipase was expressed in 50ml terrific broth medium (TB) and the expression induced with 1mM IPTG. Lipase activity assay using p-nitrophenyl esters showed that all three signal peptides directed the secretion of T1.2RQ lipase into the extracellular medium. Signal peptide, LipA, resulted in the highest extracellular activity of 5.6 U/mL, which corresponds to a 6-fold increase over the parent B. subtilis WB800 strain. Meanwhile, signal peptides, AmyQ and Epr produced 4.2 U/mL and 3.4 U/mL activity respectively. SDS-Zymogram analysis confirmed that T1.2RQ lipase was correctly processed and secreted in its original size of 44 kDa. An attempt to further increase lipase expression level by promoter optimization showed that, contrary to expectation, promoter Pgrac100 exhibited similar expression levels as the original Pgrac01. Nevertheless, the demonstration of the successful secretion of T1.2RQ lipase in this work confirms the latter as a promising approach for the industrial production of the enzyme
Keyword: Bacillus subtilis, Expression, Extracellular, Heterologous, Lipase, Thermostable