Polyhydroalkanoates (PHAs) Production from Saponified Sunflower Oil in Mixed Cultures under Aerobic Condition

Abstract

Satu kajian makmal telah dijalankan bagi menentukan keadaan yang optimum bagi penghasilan polihidroksialkanoat (PHA) menggunakan minyak bunga matahari (MB) tersaponifikasi. Sistem ini telah dijalankan semasa keadaan fasa terjujuk berterusan bagi pertumbuhan dan pengumpulan. Tujuan saponifikasi ke atas MB adalah untuk meningkatkan kualiti konstituen PHA (e.g. kopolimer bagi unit hidroksil) seperti hidroksibutirat (HBs), hidroksivalerat (HVs) dan hidroksiheksanoat (HHs). Kandungan utama MB adalah asid lemak rantai panjang (ALRP) di dalam kumpulan asid lemak tak tepu (C14:1 - C18:3) dan penghasil PHA yang terpilih akan dihasilkan semasa pertumbuhan tak seimbang (keadaan feast-famine). Operasi suap-kelompok selama hampir 6 bulan di bawah keadaan aerobik dinamik (dengan pelbagai keadaan operasi) dapat meningkatkan penghasilan PHA sehingga 33% jisim sel kering. Ia juga menunjukkan bahawa lumpur yang melalui keadaan aerobik di dalam kultur campuran mampu mengumpulkan jumlah PHA yang tinggi melalui manipulasi panjang kitaran (kajian masa penahanan hidrolik). Kadar penyimpanan spesifik PHA yang tinggi (qpfeast = 0.5 C-mol/C-mol. h) serta kandungan lumpur PHA tinggi dicapai dengan menggunakan kultur campuran menjadikan MB tersaponifikasi ini kompetitif berbanding dengan yang dihasilkan dengan menggunakan minyak sayuran yang lain (minyak jagung, kacang soya dan lain-lain). Kata kunci: Minyak bunga matahari tersaponifikasikan (MB), polihidroksialkanoat (PHA), rejim feast–famine, kultur campuran A laboratory study was conducted to assess the optimal conditions for polyhyroxyalkanoates (PHA) production using saponified sunflower oil (SO). The system was operated under continuous sequential phase of growth and accumulation conditions. The main purposed of using saponified SO was to improve the quality of PHA constituents (e.g. copolymer of hydroxyl-unit) such as hydroxybutyrates (HHBs), hydroxyvalerates (HHVs) and hydroxyhexanoates (HHs). Typically, SO mainly contains long-chain-fatty-acid (LCFA) with unsaturated fatty acid (C14:1 - C18:3) and therefore, the selected PHA-producer would be developed during unbalanced growth (feast-famine condition). Operation of the fed-batch for almost 6 months under aerobic dynamic conditions (with various operating conditions) has increased the PHA production up to 33% of dried cell weight. It was also shown that sludge subjected to aerobic condition in mixed cultures could accumulate high amount of PHA by manipulating the cycle length (HRT study). The high specific PHA storage rate (qpfeast = 0.5 C-mol/C-mol. h) as well as the high sludge PHA contents achieved by mixed cultures make this saponified SO competitive with those based on the other vegetable oil (e.g. corn oil, soy oil, etc.) Key words: Saponified sunflower oil (SO), polyhydroxyalkanoates (PHAs), feast–famine regimes, mixed cultures