Optimasi Ekstraksi Fikoeritrin dari Kappaphycus alvarezii menggunakan Ultrasonikasi dengan Pendekatan Response Surface Methodology (RSM)

Abstract

Pemanfaatan Kappaphycus alvarezii di Indonesia masih berfokus pada produksi karaginan, sehingga pigmen bernilai tinggi misalnya R-fikoeritrin (R-PE) berpotensi terbuang selama pengolahan. Pigmen R-PE merupakan protein pigmen larut air yang bernilai untuk pewarna alami dan komponen antioksidan, namun ekstraksinya memerlukan strategi ekstraksi yang efektif karena terperangkap dalam matriks dinding sel kaya gel karaginan serta sensitif terhadap kondisi proses. Penelitian ini bertujuan menentukan kondisi optimum ekstraksi R-PE dari biomassa basah K. alvarezii menggunakan ultrasound-assisted extraction (UAE) melalui Response Surface Methodology (RSM)–Central Composite Design (CCD) pada variasi suhu, waktu, dan rasio pelarut terhadap padatan biomassa (LSR), dengan tetap mengendalikan kadar karaginan yang terekstrak (carrageenan yield; CY) sebagai indikator kehilangan karaginan dari biomassa. Optimasi dilakukan menggunakan CCD sebanyak 20 run dengan tiga faktor, yaitu suhu 13–47 °C, waktu 20–70 menit, dan LSR 2–18 v/b. Respons yang dianalisis meliputi konsentrasi R-PE (R-PEC), yield R-PE (R-PEY), indeks kemurnian R-PE (R-PEPI), serta kadar karaginan yang terekstrak (CY). Kondisi optimum ditetapkan menggunakan fungsi desirability, kemudian diverifikasi secara eksperimental dan dibandingkan dengan UAE kontrol serta maserasi. Ekstrak terpilih kemudian dimurnikan melalui presipitasi amonium sulfat 60% dan dialisis, lalu dievaluasi spektrum UV–Vis, warna CIELAB, profil protein SDS-PAGE, aktivitas antioksidan (ABTS dan DPPH), serta residu pasca-ekstraksi. Kondisi optimum diperoleh pada 20 °C, 30 menit, dan LSR 12 v/b dengan desirability 0,822; seluruh respons hasil verifikasi berada pada selang kepercayaan 95% sehingga model dinyatakan valid. Kondisi UAE optimum menghasilkan ekstrak kasar terbaik dengan R-PEC 0,028 mg/mL, R-PEY 0,334 mg/g, dan R-PEPI 0,250. Setelah pemurnian, fraksi R-PE mencapai R-PEC 1,833 mg/mL, R-PEPI 0,666, dan recovery 72,65%, serta menunjukkan aktivitas antioksidan paling kuat (IC50 ABTS 13,77 µg/mL; IC50 DPPH 21,12 µg/mL). Residu kering tidak berbeda nyata antar metode (8–9 g/100 g biomassa basah), menandakan UAE teroptimasi tidak menyebabkan kehilangan biomassa struktural berlebih. Temuan ini menunjukkan UAE teroptimasi efektif menghasilkan R-PE berkualitas lebih baik dalam waktu singkat, sekaligus menyisakan residu yang berpotensi untuk pemanfaatan lanjutan.

Indonesia’s utilization of Kappaphycus alvarezii remains largely centered on carrageenan production, which may result in the loss of high-value pigments, such as R-phycoerythrin (R-PE), during processing. R-PE is a water-soluble chromoprotein with considerable value as a natural colorant and antioxidant ingredient; however, its extraction requires an effective strategy because the pigment is entrapped within a carrageenan gel-rich cell wall matrix and is sensitive to processing conditions. This study aimed to determine the optimum conditions for R-phycoerythrin (R-PE) extraction from wet K. alvarezii biomass using ultrasound assisted extraction (UAE) optimized through Response Surface Methodology (RSM) with a Central Composite Design (CCD) by varying temperature, extraction time, and the rasio-to-solid biomass ratio (LSR), while controlling the co-extracted carrageenan (carrageenan yield; CY) as an indicator of carrageenan loss from the biomass. Optimization was performed using a 20-run CCD with three factors: temperature (13–47 °C), extraction time (20–70 min), and LSR (2–18 v/b). The evaluated responses included R-PE concentration (R-PEC), R-PE yield (R-PEY), R-PE purity index (R-PEPI), and CY. The optimum condition was identified using a desirability function, experimentally verified, and compared with the UAE control and maceration. The selected extract was subsequently purified by 60% ammonium sulfate precipitation, followed by dialysis, and further characterized in terms of UV–Vis spectra, CIELAB color parameters, SDS–PAGE protein profile, antioxidant activity (using the ABTS and DPPH assays), and post-extraction residues. The optimum condition was obtained at 20 °C, 30 min, and LSR 12 v/b, with a desirability of 0.822; all verified responses fell within the 95% confidence interval, confirming the model's validity. Under optimal UAE conditions, the best crude extract was obtained, with an R-PEC of 0.028 mg/mL, an R-PEY of 0.334 mg/g, and an R-PEPI of 0.250. After purification, the R-PE fraction reached an R-PEC of 1.833 mg/mL and an R-PEPI of 0.666, with a recovery of 72.65%, and exhibited the strongest antioxidant activity (IC50 ABTS 13.77 µg/mL; IC50 DPPH 21.12 µg/mL). The dry residue did not differ significantly among extraction methods (8–9 g/100 g wet biomass), indicating that optimized UAE did not cause excessive loss of structural biomass. Overall, these findings demonstrate that optimized UAE enables rapid production of higher-quality R-PE while leaving a residue that remains amenable to further valorization.