Abdul Karim, Mohamed Ismail

Hassan, Mohd Ali

Shirai, Yoshihito

Universiti Putra Malaysia Institutional Repository

UPM Research Report 1998: Volume 2PRODUCTION OF POLYHYDROXYALKANOATESFROM PALM OIL MILL EFFLUENTM.A. Hassan, Y. Shirai and.M'I. Abdul KarimFaculty of Food Science and BiotechnologyUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: polyhydroxyalkanoates, bioplastics, palmoil mill effluent, PHA, POME.IntroductionPolyhydroxyalkanoates (PHA), accumulated in microbialcells as carbon and energy reserve materials, possess char-acteristics similar to conventional plastics. However, thesebacterial plastics are biodegradable upon disposal in the envi-ronment - hence they are also referred to as biodegradableplastics or simply as bioplastics. Unfortunately, the cost ofproducing PHA is currently more than five times that ofnormal petrochemical-based plastics, which limits theirwidespread usage. The high cost is mainly due to the cost ofraw materials and extraction/recovery of the PHA from thebacterial cells. Our strategy to reduce the overall productioncost of PHA is by coupling its production with wastewatertreatment. In our previous work, we have shown that palm oilmill effluent (POME) could be subjected to partial anaerobictreatment to yield organic acids (Hassan et al. 1996). Theobjective of this work was to produce PHA from POMEthrough the organic acids route.Materials and MethodsPOME was first converted anaerobically to organic acids bypalm oil sludge and later the acids were converted to PHA bya photosynthetic bacterium. In the first step, POME wasadded to an equal amount of sludge and treated anaerobicallyat pH 6.5 with mild mixing. Samples were taken daily andanalysed for individual organic acids and residual ammo-nium content. The treatment was terminated when the totalorganic acids were maximum. The mixture was then sedi-mented by hydroxide precipitation, and the supernatant was210used as the substrate for the PHA-producing·bacterium in thesecond step. A glass photo-bioreactor was used. Lighting wasprovided and the temperature was controlled at 30°C. Afteran initial batch operation, continuous fermentation was car-ried out at different retention times until steady state wasachieved. Organic acids and PHA were detected by HPLCand cell weight was measured by the oven method. Commer-cially available test kits detected ammonium and phosphate.Results and DiscussionDuring anaerobic treatment of POME at pH 6.5, about 12-15gIL organic acids could be produced. The main organic acidswere acetic and propionic acids. Results showed that no PHAwas produced when anaerobically treated POME containingsludge particles was used. This could be due to poor lightpenetration, whereby the photosynthetic bacteria would bedeprived of the energy source required for growth. When thesludge particles were removed, PHA could be continuouslyproduced from the organic acids obtained in the first step. At14 days retention time, the total cell concentration reached 3gIL, with more than 1 gIL of PHA at steady state. When theretention time was increased to 40 days, more than 2 gIL ofPHA was produced, corresponding to more than 60% of drycell weight. The effect of C/N was also important. When theC/N ratio was increased from 12 to 32, the cell PHA contentincreased from 30% to 60%. It was also observed that appro-priate nitrogen and phosphate concentrations were necessaryfor optimal cell growth and PHA concentration.ConclusionsThe results of this study showed that PHA could be producedfrom POME through the organic acids route.ReferencesHassan, M.A., Shirai, Y., Kusubayashi, N., Abdul Karim, M.I., Na-kanishi, K. and Hashimoto, K. 1996. Effect of organic acid pro-files during anaerobic treatment of palm oil mill effluent on theproduction of polyhydroxyalkanoates by Rhodobacter sphaeroi-des. J. Ferment. Bioeng. 82(2): 151-156.Supponed by lRPA Grant 03-02-04-0027

Production of polyhydroxyalkanoates from palm oil mill effluent

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Production of polyhydroxyalkanoates from palm oil mill effluent

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