Electronic Theses and Dissertation

Mikroalga Nannochloropsis sp. berpotensi sebagai sumber biomassa dan senyawa bioaktif, termasuk pigmen dengan aktivitas antioksidan, namun pengaruh nutrien terhadap pertumbuhan dan kemampuan antioksidannya masih perlu diteliti. Penelitian ini bertujuan mengevaluasi pengaruh variasi konsentrasi NaNO₃ (0,02%, 0,04%, dan 0,08%) dan NaH₂PO₄ (0,004%, 0,008%, dan 0,01%) terhadap akumulasi biomassa serta aktivitas antioksidan ekstrak pigmen. Pertumbuhan biomassa diamati dari jumlah sel. Pigmen diekstraksi menggunakan etanol dan dianalisis dengan metode spektrofotometri UV-Vis. Aktivitas antioksidan dievaluasi melalui metode diphenyl-1-picrylhydrazyl (DPPH). Hasil menunjukkan bahwa penambahan NaNO₃ 0,04% dan NaH₂PO₄ 0,004% menghasilkan biomassa tertinggi, namun aktivitas antioksidan tergolong lemah karena rendahnya karotenoid dan dominasi klorofil. Produksi karotenoid tertinggi diperoleh pada NaH₂PO₄ 0,01%. Sumber N dan P sangat berpengaruh dalam produksi biomassa mikroalga Nannochloropsis sp. tetapi tidak signifikan dalam produksi antioksidan.

The microalgae Nannochloropsis sp. can be a source of biomass and bioactive compounds, including pigments with antioxidant activity. Their production depends on nutrient composition, so further studies are needed. This study evaluated the effects of different concentrations of NaNO₃ (0.02%, 0.04%, 0.08%) and NaH₂PO₄ (0.004%, 0.008%, 0.01%) on biomass accumulation and antioxidant activity of pigment extracts. Cell growth was measured by optical density at 680 nm and dry cell weight. Pigments were extracted with ethanol and analysed by UV-Vis spectrophotometry. Antioxidant activity was measured using the diphenyl-1-picrylhydrazyl (DPPH) method. NaNO₃ 0.04% and NaH₂PO₄ 0.004% produced the highest biomass, but antioxidant activity was weak, likely because carotenoid content was low and chlorophylls dominated. The highest carotenoid production was observed at 0.01% NaH₂PO₄. These results suggest that while N and P concentrations significantly affect biomass and pigment composition, optimising for biomass does not necessarily improve antioxidant potential in Nannochloropsis sp.