Electronic Theses and Dissertation

Penelitian ini bertujuan untuk mengisolasi lignin dari batang tanaman karet (Hevea
brasiliensis) menggunakan metode kraft dan mensintesis kompleks Zn-lignin (ZnL)
dari lignin hasil isolasi dan lignin komersial. Sintesis dilakukan dengan beberapa
variasi volume larutan Zn, namun hanya sampel dengan volume 7,65 mL yang dipilih
untuk dianalisis lebih lanjut menggunakan FTIR, XRD, SEM-EDS, NMR, serta uji
toksisitas dan antimikroba. Lignin kraft berhasil diisolasi dan kompleks ZnL terbentuk,
dibuktikan dengan kandungan Zn sebesar 2,49% pada Zn-lignin komersial dan 6,39%
pada Zn-lignin kraft berdasarkan EDS. Spektrum FTIR menunjukkan perbedaan
karakteristik antara lignin kraft (hardwood) dan lignin komersial (softwood),
khususnya pada pita –OH yang bergeser setelah kompleksasi. Hasil XRD
menunjukkan bahwa pola difraksi lignin dan kompleksnya hampir serupa, namun
intensitas puncaknya menjadi lebih tumpul setelah pengomplekkan. Data NMR
menunjukkan keberadaan sinyal khas gugus aromatik, metoksil, dan karbonil,
mengonfirmasi struktur fenilpropanoid pada lignin hasil isolasi. SEM memperlihatkan
perubahan morfologi menjadi lebih padat dan halus setelah kompleksasi. Uji toksisitas
menunjukkan bahwa Zn-lignin komersial paling toksik (LC₅₀ = 460,56 ppm),
sedangkan lignin kraft paling rendah toksisitasnya (LC₅₀ = 10247,79 ppm). Uji
antimikroba menunjukkan hanya lignin kraft yang aktif terhadap Staphylococcus
aureus pada konsentrasi tertinggi, dan terhadap Candida albicans pada semua
konsentrasi. Penelitian ini menunjukkan bahwa lignin kraft memiliki aktivitas biologis
lebih baik, dan sintesis kompleks ZnL masih dapat dioptimalkan lebih lanjut.

This study aims to isolate lignin from rubber tree trunks (Hevea brasiliensis) using the kraft method and synthesize Zn-lignin (ZnL) complexes from isolated lignin and commercial lignin. Synthesis was carried out with several variations in the volume of Zn solution, but only a sample with a volume of 7.65 mL was selected for further analysis using FTIR, XRD, SEM-EDS, NMR, and toxicity and antimicrobial tests. Kraft lignin was successfully isolated and the ZnL complex was formed, as evidenced by the Zn content of 2.49% in commercial Zn-lignin and 6.39% in kraft Zn-lignin based on EDS. The FTIR spectrum shows differences in characteristics between kraft lignin (hardwood) and commercial lignin (softwood), especially in the –OH band which shifts after complexation. XRD results show that the diffraction patterns of lignin and its complex are almost similar, but the peak intensity becomes duller after complexation. NMR data showed the presence of typical signals of aromatic, methoxyl, and carbonyl groups, confirming the phenylpropanoid structure of the isolated lignin. SEM showed changes in morphology to become denser and smoother after complexation. Toxicity tests showed that commercial Zn-lignin was the most toxic (LC₅₀ = 460.56 ppm), while kraft lignin had the lowest toxicity (LC₅₀ = 10247.79 ppm). Antimicrobial tests showed that only kraft lignin was active against Staphylococcus aureus at the highest concentration, and against Candida albicans at all concentrations. This study showed that kraft lignin had better biological activity, and the synthesis of ZnL complexes could still be further optimized.