Polihidroksialkanoat (PHA) adalah polimer biodegradasi yang telah menarik minat di kalangan penyelidik akhir-akhir ini. Selaras dengan itu, sintesis PHA dalam mikroorganisma merawat air sisa kilang minyak sawit (POME) mempunyai prospek yang menarik. Butiran aerobik yang dihasilkan dengan menggunakan POME belum diterokai untuk sintesis PHA sehingga kini. POME (dicerna secara acidogenik) untuk kajian ini dikumpul dari tasik rawatan anaerobik di kilang kelapa sawit. Hasil kajian ini menunjukkan bahawa butiran aerobik telah berjaya dihasilkan dengan POME yang dicerna secara acidogenik dalam 9 hari dan pada masa yang sama, 85 % suapan COD berjaya disingkirkan secara purata. Butiran aerobik mempunyai purata indeks isipadu enapcemar (SVI) 48 mL/g. Manakala, kandungan substrat polimerik sel (EPS) dalam butiran aerobik menunjukkan kandungan protin adalah lebih tinggi berbanding karbohidrat. Selain itu, analisa 16S rRNA menunjukkan genera Bacillus dan Bordetella mendominasi kumpulan bakteria dalam butiran aerobik tersebut. Analisa berikutnya mendedahkan bahawa butiran aerobik dapat menumpuk PHA disamping merawat POME. Purata kandungan PHA adalah 0.68 g PHA/g CDW dan PHA yang terkumpul adalah poli-3-hidroksibutirat-co-hidroksivalerat (P3(HB-co-HV)). Kajian yang seterusnya mendedahkan bahawa masa kitaran 6 jam dan strategi penyuapan aerobik dinamik (ADF) menumpuk kandungan PHA yang tertinggi (0.651 g PHA/g CDW) berbanding strategi yang lain. Sementara itu, kajian penyarian PHA mendedahkan bahawa kaedah serakan natrium hipoklorit-kloroform adalah pilihan yang terbaik berbanding dengan tiga kaedah yang lain. Penyingkiran hampir kesemua lapisan EPS dalam butiran aerobik dikenalpasti sebagai elemen utama dalam penyarian PHA daripada butiran aerobik. Hasil PHA yang diperoleh adalah 0.89 g PHA/g CDW dengan menggunakan kaedah serakan natrium hipoklorit-kloroform. Sebaliknya, kitaran pertumbuhan-perpecahan didapati mempengaruhi jumlah keupayaan penumpukan PHA. Butiran aerobik di antara 0.35 dan 0.5 mm menumpuk 0.68 g PHA/g CDW berbanding dengan 0.60 g PHA/g CDW dalam butiran aerobik lebih besar daripada 2 mm. Resapan substrat dan oksigen ke dalam butiran aerobik didapati sebagai penyebab kepada perbezaan ini. Peningkatan kepekatan substrat dari 0.91 hingga 3.64 kg COD/m3.hari telah meningkatkan kandungan PHA daripada 0.66 ke 0.87 g PHA/g CDW. Manakala, peningkatan kadar pengudaraan dari 1 ke 4 L/min telah mempercepatkan penumpukan PHA maksimum, tanpa mempengaruhi jumlah kandungan PHA dalam butiran aerobik. Manakala, sisa minyak didapati melekat pada permukaan butiran aerobik dan seterusnya menghadkan peresapan substrat. Akibatnya, kandungan PHA telah menurun. Pemalar perencatan didapati bernilai 5.61 g/L sisa minyak. Hasil keseluruhan kajian ini menumpu ke arah penumpukan PHA dalam butiran aerobik.
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Polyhydroxyalkanoate (PHA) is a biodegradable polymer which has attracted a lot of interests among researchers lately. In tandem with that, PHA synthesis in microorganisms treating palm oil mill effluent (POME) is an interesting prospect. Aerobic granules developed using POME are totally unexplored till date for PHA synthesis. POME (acidogenically digested) used in this study was collected from an existing anaerobic pond of palm oil mill wastewater treatment plant. The findings of this study showed that aerobic granules were successfully developed using acidogenically digested POME within 9 days and 85 % of the influent COD was removed on average. The developed aerobic granules had an average sludge volume index (SVI) of 48 mL/g. The extracellular polymeric substance (EPS) in aerobic granules contained higher proportion of protein than carbohydrate. Besides that, 16S rRNA analysis indicated that Bacillus and Bordetella genera were the dominating group of bacteria in aerobic granules developed using acidogenically digested POME. The ensuing analysis reveals that aerobic granules were able to accumulate PHA during the treatment of acidogenically digested POME. The average PHA content was 0.68 g PHA/g CDW and the PHA accumulated was co-polymer of poly-3-hydroxybutyrate-co-hydroxyvalerate (P3(HB-co-HV)). The subsequent study reveals that at the cycle time of 6 hrs, the aerobic dynamic feeding (ADF) strategy accumulates the highest PHA (0.651 g PHA/g CDW) of all other strategies. Meanwhile, the PHA recovery study reveals that the sodium hypochlorite-chloroform dispersion method is the best choice compared to other three methods used. The key element in recovering PHA from aerobic granules found to be nearly complete removal of EPS layer in the aerobic granules. The PHA recovery yield was 0.89 g PHA/g CDW in the sodium hypochlorite-chloroform dispersion method. On the other hand, the growth-disintegration processes found to influence the amount of PHA accumulating capability. Granules in between 0.35 and 0.50 mm accumulated 0.68 g PHA/g CDW compared to 0.60 g PHA/g CDW in granules larger than 2 mm. Substrate and oxygen diffusion into the aerobic granules found to be the reason for this difference. Increase of organic loading rate (OLR) from 0.91 to 3.64 kg COD/m3.day has increased the PHA content from 0.66 to 0.87 g PHA/g CDW, respectively. Meanwhile, increase of aeration rate from 1 to 4 L/min has accelerated the formation of PHA only, whereas the PHA content in aerobic granules remained constant. The residual oil was found to attach on the surface of aerobic granules and subsequently limits the substrate diffusion which in turn decreased the PHA content. The inhibition constant was 5.61 g/L residual oil. The overall outcome of this study converges towards the successful PHA accumulation in aerobic granules.
Accumulation and extraction of polyhydroxyalkanoate from aerobic granules treating palm oil mill effluent_Gobi Kanadasan _K4_2015_MYMY