Pemberbukuan dirangsang pH mikroalga Scenedesmus dimorphus dikaji dalam kajian ini untuk menyiasat kebolehlaksanaannya dalam pemulihan mikroalga bagi pengeluaran hiliran bioetanol. Mikroalga Scenedesmus dimorphus dipilih atas keupayaan cemerlang dalam pengumpulan kanji dalam sel. Kajian ini dibahagikan kepada 4 bahagian: kultivasi mikroalga, pengawasan pertumbuhan mikroalga, pencirian kandungan kanji mikroalga dan pemberbukuan dirangsang pH mikroalga dengan fokus pada 3 parameter: pH media kultur, isi padu pemendapan mikroalga dan masa pemendapan mikroalga. Berdasarkan kajian awal reagen kimia, Ca(OH)2 ialah reagen kimia terbaik bagi pemberbukuan dirangsang pH kerana pembentukan mendakan CaCO3 merangsang pemberbukuan sapuan mikroalga. Eksperimen selanjutnya dengan penggunaan Ca(OH)2 memberikan pemulihan mikroalga dalam julat 27.8%-95.7% bagi pH media kultur, isi padu pemendapan mikroalga dan masa pemendapan mikroalga yang berbeza. Pemberbukuan dirangsang pH optimum berlaku pada pH media kultur 10, isi padu pemendapan mikroalga 200mL dan masa pemendapan mikroalga 10 minit dengan pemulihan mikroalga 91.1%. Kehilangan kandungan kanji mikroalga dalam pemberbukuan dirangsang pH diimbangi oleh pemulihan mikroalga yang tinggi. Pandangan mikroskop selanjutnya membuktikan bahawa pemberbukuan dirangsang pH ialah cara pemisahan mikroalga yang sesuai bagi mikroalga Scenedesmus dimorphus sebelum pengeluaran hiliran bioetanol.
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The pH induced flocculation of Scenedesmus dimorphus strain microalgae was studied in this research to investigate its feasibility to recover microalgae for downstream bioethanol production. Scenedesmus dimorphus strain microalgae was selected due to their excellent ability in accumulating starch in their cells. The research was split into 4 sections: microalgae cultivation, microalgae growth monitoring, microalgae starch content characterization and pH induced microalgae flocculation with focus on 3 process parameters: culture medium pH, microalgae settling volume and microalgae settling time. Based on chemical reagent prescreening, Ca(OH)2 was the best chemical reagent for pH induced microalgae flocculation as CaCO3 precipitates formation induced sweeping flocculation of microalgae. Further experiments using Ca(OH)2 yielded a range of microalgae recovery (27.8%-95.7%) at different culture medium pH, microalgae settling volume and microalgae settling time. The optimum pH induced flocculation occurred at culture medium pH10, 200mL microalgae settling volume and 10 minutes microalgae settling time, giving 91.1% microalgae recovery. The lost of microalgae starch content in pH induced flocculation was compensated by the high microalgae recovery. Further microscopic view of microalgae vindicated that pH induced flocculation was indeed a viable microalgae separation method for Scenedesmus dimorphus strain microalgae prior to downstream bioethanol production.
Scenedesmus dimorphus strain microalgae as feedstock for bioethanol production optimum conditions for pH induced flocculation / Beh Jyh Jiunn