Judul: Characteristics of Sugarcane Leaves Lignin Isolated with Maleic Acid
Abstrak: Perbedaan konsentrasi dan pH asam maleat (MA) ketika isolasi lignin mempengaruhi karakteristik lignin daun tebu (SCL). Penelitian ini bertujuan menentukan karakteristik kimia lignin hasil isolasi SCL dengan perlakuan perbedaan konsentrasi dan pH larutan MA, menentukan perlakuan optimum yang menghasilkan lignin dengan karakteristik kimia terbaik, serta menganalisis sifat fisikokimia, morfologi, dan termal lignin hasil isolasi dengan perlakuan optimum. Lignin hasil isolasi konsentrasi MA10% menghasilkan kadar abu yang tinggi, sehingga menurunkan kemurniannya. Lignin isolasi dengan kombinasi MA5% pH 3 merupakan lignin yang optimum dengan mempertimbangkan konsep green chemistry dengan jumlah MA untuk isolasi ligninnya lebih sedikit. Nilai kadar total phenolik dan antioksidan yang lebih rendah menandakan kemampuan membentuk gugus hidroksi fenolik yang kurang baik. FTIR menunjukkan terdapat gugus O-H, -CH3 dan -CH2, C=O tak terkonjugasi, C=C (aromatik), dan C-O pada unit guaiasil. Analisis sifat termal menunjukkan bahwa MA5% pH 3 memiliki stabilitas termal yang rendah yang sejalan dengan hasil berat ekuivalen yang rendah dengan kandungan siringil lebih tinggi dibandingkan dengan guiasil. Lignin MA5% pH 3 mengandung karbon dan oksigen akibat proses isolasi dengan asam maleat, serta natrium akibat proses ekstraksi dengan NaOH., The difference in the concentration and pH of maleic acid (MA) when lignin is isolated can affect the characteristics of sugarcane trash lignin (SCL). This study aimed to determine the chemical characteristics of lignin isolated from SCLs with different MA solution concentrations and pH values. It was also to determine the optimum treatment that produces lignin with the best characteristics, and analyze the physicochemical, morphological, and thermal properties of lignin isolated with the optimum treatment. Lignin isolated from MA10% produced a high ash content, thus reducing its purity. Lignin isolated with a combination of MA at 5% and pH 3 was considered the optimum lignin by considering the concept of green chemistry and using less MA for lignin isolation. A lower Total phenolic content (phOH) and antioxidant activity indicated a poor ability to form phenolic hydroxy groups. FTIR showed the presence of O-H, -CH3 and -CH2 groups, unconjugated C=O, C=C (aromatic), and C-O on guaiacyl units. The thermal analysis showed low thermal stability, which aligned with the low equivalent weight results with a higher syringyl content compared to that of guiacyl. Lignin MA (5%, pH 3) contained carbon and oxygen from the MA isolation process and sodium from the NaOH extraction.
Keyword: Isolasi lignin, Iradiasi gelombang mikro, Konsentrasi asam maleat, Lignin daun tebu, Perbedaan pH

Judul: Sugarcane Leaf Lignin Characteristics Isolated with a Low Acid Concentration
Abstrak: Lignin daun tebu merupakan salah satu komponen biomassa yang berpotensi sebagai sumber bahan kimia alami. Sifat kimia dan metode isolasi mempengaruhi sifat bioproduk. Penelitian ini bertujuan mengkaji pengaruh metode sekeunsial pra-perlakuan daun tebu dan metode isolasi lignin terhadap rendeman isolasi lignin, sifat fisikokimia dan termal. Padatan kemudian dikarakterisasi fisikokimia dan termal (TGA dan DSC). Hasil penelitian menunjukkan kadar αselulosa pra-perlakuan asam microwave-basa autoclave lebih tinggi dibandingkan dengan pra-perlakuan asam microwave-basa microwave dengan kelarutan hingga mencapai 94%. Hasil isolasi pra-perlakuan asam microwave-basa microwave lebih tinggi dibandingkan dengan pra-perlakuan asam microwave-basa autoclave yang mencapai diatas 68%. Lignin hasil isolasi kedua proses pra-perlakuan memiliki nisbah S/G yang sama. Isolat lignin menunjukkan keberhasilan proses isolasi yang ditandai dengan adanya gugus fungsi penciri lignin dalam spektra FTIR seperti - CH, C=O dan C-O. Analisis TGA lignin masing-masing pra-pelakuan memiliki karakteristik degradasi termal yang sama. Analisis DSC menunjukkan adanya satu titik transisi glass (Tg) dengan masing-masing suhu Tg hasil pra-perlakuan asam microwave -basa microwave dan asam microwave-basa autoclave yaitu 128,44 oC dan 131,02 oC, Sugarcane leaf lignin is one of the chemical components of biomass that have prospects for natural chemicals. The chemical characteristics and the isolation method of lignin influence the bioproduct properties. The research examined the effect of the sequential pre-treatment method of sugarcane leaf and lignin isolation method on isolated lignin's yield, physicochemical and thermal characteristics. The pulp was then characterized by the chemical component and the yield, while the isolated lignin was analyzed the physicochemical and the thermal (TGA, DSC) characteristics. The results showed that the cellulose content of pretreated with acid microwave-alkaline autoclave was higher than the pre-treatment of the acid microwave-alkaline microwave with the lignin removal reached up to 94 %. The yield of isolated lignin derived from acid microwave-alkaline microwave was higher than the pre-treatment of acid microwave-alkaline autoclave, which was reached 68 %. The isolated lignin from both pre-treatment methods has the same S/G ratio. FTIR spectra indicate the functional groups of typical lignin such as -CH, C=O, and CO, indicating the isolation method's success. TGA analysis of lignin indicated that both lignins have similar thermal degradation characteristics. In contrast, DSC analysis showed a glass transition (Tg) with each Tg temperature to sugarcane trash lignin from the acid microwave-alkaline microwave and acid microwave-alkaline autoclave were 128.44 °C and 131.02 °C, respectively.
Keyword: Daun tebu, fraksionasi bertahap, iradiasi gelombang mikro, karakteristik lignin, pemanasan autoclave, autoclave heating, characteristics of lignin, gradual fractionation, microwave irradiation, sugarcane leaf

Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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