ORIGINAL ARTICLES Palm oil mill effluent: a waste or ...

466 Journal of Applied Sciences Research, 8(1): 466-473, 2012 ISSN 1819-544X This is a refereed journal and all articles are professionally screened and reviewed

ORIGINAL ARTICLES Palm oil mill effluent: a waste or a raw material? 1,2

Aliyu Salihu and 1Md. Zahangir Alam

1

Bioenvironmental Engineering Research Unit (BERU), Department of Biotechnology Engineering, Faculty of Engineering, International Islamic University Malaysia (IIUM), 50728 Kuala Lumpur, Gombak, Malaysia. 2 Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria ABSTRACT Environmental issues are increasingly becoming more important globally. Large quantities of Palm oil mill effluent (POME) are generated annually during crude palm oil production. In this review, POME was considered as a biphasic product; being a major source of pollution in Malaysia due to its high organic load and as a cheap renewable residue which has been found to be useful in the production of fertilizers, citric acid, bioethanol, biohydrogen, bioplastic, hydrolytic enzymes, among others. Some of the benefits that can be derived from these productions include lower production cost, less waste and reduced energy consumption. Thus, recent advances in biotechnology could offer better solutionsto POME treatment by using it as a raw material to develop some valueadded products. Key words: Palm oil mill effluent, pollution, raw material, value-added products. Introduction The oil palm in Malaysia is over a century old, although palm plant was commercially exploited as an oil crop from 1911 when the first palm oil estate was established(Basiron and Weng, 2004). The effluent produced during palm oil production is a viscous acidic brown liquid, predominantly organic and non-toxic in nature with highly unpleasant odour called palm oil mill effluent (POME)(Kathiravale and Ripin, 1997). Malaysia being amongst the largest producers and suppliers of palm oil in the world had estimated annual production figures in 2000 and 2008 as 8.3 and 16.3 million tonnes respectively (Foo and Hameed, 2010)with a total of 423 mills producing up to 89 million tonnes of oil palm fresh fruit bunches per year(Vairappan and Yen, 2008). This resulted in annual generation of POME of about 66.8 million tonnes(Vairappan and Yen, 2008). Thus, it was estimated that for every 100 tonnes of fresh fruit bunches processed, 78 tonnes ended up as wastes(Vikineswary et al., 1997).Direct discharge of untreated POMEinto aquatic environments may cause some pollution problems;as such its treatment requires efficient and rapid technology(Singh et al., 2010). Bioconversion denotes biological transformation of waste and/or the reformationof complex organic waste into a valuable metabolite using biological processes or microorganisms i.e. Bacteria, yeast and fungi. Several microbial species have been known for their ability to break down organic materials present in waste by producing value added products(Alam et al., 2007).Renewable resources including agricultural and industrial residues have been studied extensively through microbial bioconversion processes. These cheap agricultural and food-processing by-products are used by most researchers as substrates in the fermentation processes to produce several products of economic importance. This review describes some of the value added products that can be generated from POME, which is in line with global awareness towards creating a clean and healthy environment through green technology. This can minimize the costs of production and effective treatment in waste management as well as full compliance with environmental regulations. Characteristics and Properties: Although, the palm industry has contributed significantly towards Malaysia foreign exchange earnings and the increase in standard of living of its population(Yusoff and Hansen, 2007), however the effluent from the industry is known to be an environmental pollutant based on its high compositions of total solids, suspended organic solids, dissolved organic matter among others as represented in Table 1. Treatment systems of POME: Malaysian palm oil industries use different treatment strategies; so as to curb the pollution of waterways that can be caused by POME. Thus, the industries are facing the challenge of balancing the environmental Corresponding Author: Aliyu Salihu, Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria.

467 J. Appl. Sci. Res., 8(1): 466-473, 2012

protection, their economic viabilities and sustainable development. Initial pre-treatment involves the use of flocculation, solvent extraction, adsorption and membrane separation processes to remove the suspended solids and residual oil and grease(Abdul Latif et al., 2003a). Abdul Latif et al. (2003b) showed the superiority of membrane separation using ultrafiltration and reverse osmosis over the use of coagulation and activated carbon adsorption for POME treatment. The latter had removal efficiencies of 97.9% turbidity, 56% COD and 71% BOD while the former yielded a higher removal efficiencies of 100% turbidity, 98.8% COD and 99.4% BOD. Table 1: Characteristics of POME and its respective standard discharge limit by Malaysian Department of Environment as described by different researchers. Parameter Ahmad et al. (2003) Najafpour et al. (2006) Choorit&Wisarnwan Standard limit (2007) (mg/L) pH 4.7 3.8-4.4 4.24- 4.66 5-9 Oil and Grease(mg/L) 4,000 4,900-5,700 8,845-10,052 50 Biological Oxygen 25,000 23,000-26,000 62,500-69,215 100 Demand (mg/L) Chemical Oxygen 50,000 42,500-55,700 95,465-112,023 Demand (mg/L) Total solids(mg/L) 40,500 68,854-75,327 Suspended 18,000 16,500-19,500 400 44,680ԟ47,140 solids(mg/L) Total Nitrogen (mg/L) 750 500-700 1,305-1,493 150 Total volatile solids 34,000 4,045-4,335 (TVS) (mg/L)

Ponding stands as the most common treatment system,which is a multi-stage process consisting of de-oiling tank, acidification ponds, anaerobic and facultative or aerobic ponds(Chan and Chooi, 1984).Thus, the capacity of the palm oil mill and the amount of effluent discharges determine the nature of the ponds. Facultative or aerobic ponds are necessary to further reduce BOD concentration in order to produce effluent that complies with the national effluent discharge standards. Although, anaerobic and facultative ponding systems are widely employed for POME treatment(Ma, 1999), however, in order to prevent the escape of methane gas generated; these systems are coupled with closed digesters, so that the generated methane can be used as an auxiliary fuel in the boilers of palm oil mill industries(Vijayaraghavan et al., 2007). Also, open digesting tanks are used for POME treatment, especially when there is limited area of land for ponding treatment. In the process of degrading POME; methane is generated through a series of reactions. The first step includes hydrolysis, where complex molecules are converted into their smaller subunits. This is then followed by acidogenesis (including acetogenesis), which involves the breakdown of the subunits by acidogenic bacteria to organic acids, hydrogen and carbon dioxide. The last step is methanogenesis, where the action of hydrogenotropic methanogens and acetoclastic methanogens results in formation of methane(Poh and Chong, 2009). The merits and demerits of alternative treatment methods are summarized in Table 2. Table 2: Advantages and disadvantages of methods employed for treatment of POME (Poh& Chong, 2009). Treatment type Advantages Disadvantages Anaerobic Minimal energy requirement (no aeration), methane gas Vast area of land required for conventional generation as a valuable product, the sludge generated digesters, longer retention time and slow start-up can be used for land application Aerobic Shorter retention time, efficient in handling toxic wastes Required higher energy (aeration), unsuitable for land application as the rate of toxic inactivation is much slower than that of anaerobic. Membrane Small area required for membrane treatment plant, Short membrane life, membrane fouling, effective and efficient treatment expensive compared to conventional treatment Evaporation The Solid concentrate formed is utilized as feed High energy consumption material for fertilizer processing

Uniqueness of POME: High concentrations of carbohydrate, protein, nitrogenous compounds, lipids and minerals present in POME (Habib et al., 1997) make it a good raw material for bioconversion through various biotechnological processes. Table 3 shows the proximate composition (%) of major constituents as well as the minerals contents of raw POME. Conversion of POME to value added products: The POME is a biphasic product which is considered as a waste but at the same time, it is utilized as a raw material in other processes. Many processing technologies for converting POME into value added products have

468 J. Appl. Sci. Res., 8(1): 466-473, 2012

been developed, these include: carotenoid, which can be further utilized for vitamin A and vitamins E (tocopherols) production(Wahid et al., 2004), citric acid(Alam et al., 2008a), fertilizer(Basiron and Weng, 2004), biodiesel(Gutiérrez et al., 2009), hydrolytic enzymes, among others. This gives positive impact by solving environmental problem besides giving value added products. Table 3: The proximate compositionand mineral contents of raw POME (Habib et al., 1997). Major constituents Composition (%) Macro-minerals Composition (µg/g dry weight) Moisture 6.99±0.14 K 8951.55±256.45 Crude protein 12.75±1.30 Na 94.57±6.45 Crude lipid 10.21±1.24 Ca 1650.09±160.45 Ash 14.88±1.35 Mg 911.95±95.50 Carbohydrate 29.55±2.44 P 14377.38±1206.88 Nitrogen free 26.39±2.33 S 13.32±1.45 extract Total carotene 0.019±0.001

Micro-minerals Fe Cu Zn Mn Mo Cr

Composition (µg/g dry weight) 11.08±2.20 10.76±1.04 17.58±2.10 38.81±3.65 6.45±0.40 4.02±0.44

Co Ni Se Si Sn Al B As V

2.40±0.35 1.31±0.30 12.32±1.35 10.50±1.80 2.30±0.30 16.60±1.44 7.60±0.60 9.09±0.65 0.12±0.02

Carotene extraction from POME: Carotene is a provitamin, which is converted in the body to a vitamin. The β-carotene is a precursor of vitamin A, whose function in the body plays major roles in the maintenance of strong bones, healthy skin, teeth and hair(Ahmad et al., 2010).It is also known as a potent antioxidant, protecting the cells against effects of free radicals in the body. In order to extract carotene from POME, the process was carried out using different solvent systems; the most important ones with high extraction potentials are petroleum ether with a mean concentration of 417.9 ppm, and n-hexane whose mean concentration was found to be 394.8 ppm(Ahmad et al., 2008). Thus, the amount of carotene extracted from POME is closely related to that obtained from the crude palm oil; whose carotene concentration ranges between 400 and 3500ppm. Carotenoids have been extensively used in food, cosmetic and pharmaceutical industries; as such their extraction and recovery from POME could be important(Ahmad et al., 2008). Bioplastic formation: Polyhydroxyalkanoates (PHAs) are thermoplastics whose excellent mechanical properties are similar to those of polypropylene. They are endowed with other additional advantages such as biodegradability, biocompatibility, and production are mainly from renewable resources (Mumtaz et al., 2010; Purushothaman et al., 2001). The PHAs are intracellular products generated by some bacteria species under nutrient limiting conditions especially in a medium rich in carbon with little or no nitrogen or phosphorus present (Hassan et al., 1996). Based on this, high organic content of POME makes it a good substrate for bioplastic production. Hassan et al. (1996) developed a two-stage process for the production of PHA using POME. The initial stage involvesthe production of organic acids (acetic and propionic acids) by anaerobic treatment of POME, followed by conversion of the produced organic acids to PHA using a phototrophic bacterium, Rhodobacter sphaeroides (IF0 12203). Thus, renewable agricultural residues coupled with highly producing microorganisms are the pre-requisites that can make the PHA production economically viable; since the types and compositions of the substrates determine the final polymer properties of the bioplastics (Mumtaz et al., 2010). Thus, use of POME as an inexpensive carbon sourceto produce PHAs may lead to some significant economic advantages. This is because substantial amount (40%) of total operating costs of PHA production could be linked to the raw materials, and more than 70% of this cost is attributed to the carbon source. Alias and Tan (2005) isolated a bacteria species from POME, which has the ability to produce poly-(3)hydroxybutyrate. The bacterium was tentatively identified as Burkholderia cepacia. Generally, wild type microorganisms do not produce a high yield of PHA to be considered for use at industrial scale, but their ability to synthesize PHA would be very important that may lead to genetic modification of the microorganisms.

469 J. Appl. Sci. Res., 8(1): 466-473, 2012

Bioethanol production: Currently, there is global interest in the utilization of biomass and wastes forbioethanol production.Countries like USA and China have initiated several biofuel programs where lignocellulosic biomass and agro-industrial residues are effectively used for production of ethanol and other biofuels. Conventionally, chemical as well as physical methods of hydrolysis are firstly used for pretreating the residues. Enzymatic treatments to convert cellulose and hemicellulose to sugars are then used; the microbial bioconversion of the produced sugar results in the formation of the final product, bioethanol (Hahn-Hagerdal et al., 2006). The utilization of bioethanol (biofuel) for transport is of importance for a number of reasons, especially with regards to environmental issues such as climate change, depletion of fossil fuel reserves, and reduction of reliance on imports (Wingren et al., 2003). Large scale production of bioethanol using lignocellulosic biomass and agro-industrial residues could reduce the reliance on fossil sources and curb some levels of environmental pollution (Rass-Hansen et al., 2007). Since, combustion of ethanol does not contribute to global warming unlike fossil fuel with atmospheric buildup of carbon dioxide in the atmosphere. Several renewable residues have been used in the production of ethanol; these include waste paper, domestic refuse (Cheung and Anderson, 1996), andlignocellulosic biomass (corn stover, crop straw, sugar cane bagasse) (Wyman, 1996). Alam et al. (2008b) studied the production of bioethanol using POME as the main substrate using Saccharomyces cerevisiae under controlled laboratory condition with an optimum yield of 16%. Also, compatible mixed cultures of Trichoderma harzianum, Phanerochaete chrysosporium, Mucor hiemalis, and S. cerevisiae resulted in bioethanol production of 4% (v/v) or 31.6 g/l based on direct bioconversion of POME. Following the determination of optimum operating conditions by two-level fractional factorial design in stirred-tank bioreactor, the highest bioethanol production was found to be 4.6% (v/v) or 36.3 g/l at a temperature of 32oC, pH of 6, and pO2 of 30% (Alam et al., 2009). Based on this, conversion of POME for bioethanol production offers a simple and effective treatment of this effluentproduced by palm oil mills. This can alleviate the competition in the utilization of food-based raw materials thereby preserving the price of food commodity. Thus, the oil palm-based residuescould provide an impetus for sustainable generation of bioethanol as well as other value added products, since palm oil production constitutes the major agricultural earnings in Malaysia (Cheng et al., 2007). Citric acid production: In an effort to utilize the palm oil industries effluent discharge, citric acid has been produced using POME as a raw material (Jamal et al., 2007).Industrial production of citric acid depends on fungal fermentation (e.g. Aspergillus niger) in the presence of glucose (or sucrose) as the main substrate using liquid and solid state fermentation techniques (Grewal and Karla, 1995). However, several cheaper substrates have been used for citric acid production by A. niger. These include inulin (Drysdale and McKay, 1995), date fruit syrup (Roukas and Kotzekidou, 1997), sugarcane molasses (Gupta, 1994,among others. All these substrates have lesser yields when compared to POME. Alam et al. (2008a) obtained the citric acid yield of 5.2 g/l from POME using a seven day fermentation period. Citric acid is used extensively in various industrial processes especially as acidulant, stabilizer, flavor enhancer, preservative, antioxidant, emulsifier and chelating agent (Jamal et al., 2005). Thus, annual production of citric acid is estimated to be about half million tonnes based on the fermentation of conventionally used raw materials (glucose and sucrose). Based on the extensive use of citric acid, several strategies have been put in place for its efficient production using agricultural residues. Efforts to achieve this goal by using POME as a new substrate proved effective (Jamal et al., 2007; Alam et al., 2008a). Medium for isolation and growth of microorganisms: Numerous microorganisms can invade and grow in POME, breaking down complex molecules into simple ones. The high organic matter in POME has contributed in the proliferation of aerobic microorganisms. The growth of Yarrowia lipolytica NCIM 3589 in raw POME led to a substantial reduction in Chemical oxygen demand (COD) within 48 hrs and the acidic pH of POME became alkaline due to utilization of fatty acids by the organism (Oswal et al., 2002). Rashid et al. (2009) isolated and purified some filamentous fungi from POME into three different genera namely Penicillium, Rhizopus and Basidiomycetes. Also, some bacterial species isolated from POME ponds at a palmoilprocessing factory, showed high potential for PHAs production based on initial staining screening experiments using Sudan Black B plates (Redzwan et al., 1997). Rhizopus oryzae and Rhizopus rhizopodiformis were thermophilicfungi isolated from POME. These fungi showed high extra- and intracellular lipase activity at 50°C (Razak et al., 1997).

470 J. Appl. Sci. Res., 8(1): 466-473, 2012

Biohydrogen production: Biohydrogen production attracts attention of researchers, as it is less energy intensive and can be coupled with wastewater treatment processes using dark-and photo-fermentation techniques. Thus, Hydrogen is characterized with a high energy yield of 122 KJ/g which is 2.75 times higher than the hydrocarbon fuels; and the only end-product is water (Chong et al., 2009). These characteristics make it a promising alternative fuel. The recent biological approach to producing hydrogen is to convert agro-industrial residues into hydrogen-rich gasthrough anaerobic processes by potential bacterial strains. As such many researchers have recognized the potential of harnessing hydrogen from POME. Central composite design was used to determine the optimum conditions for hydrogen production using POME by Clostridium butyricum EB6. The maximum hydrogen yield of 914 ml H2/h was obtained at the optimum conditions of pH, temperature and chemical oxygen demand (COD) of 6.52, 41oC and 60g COD/l respectively (Chong et al., 2009). Also, thermophilicmicroflora was studied by O-Thong et al. (2007) in anaerobic sequencing batch reactor for hydrogen production using POME. The supplementation by nitrogen, phosphorus and iron sources resulted in significant increment of hydrogen production yield from 1.6±0.1 to 2.24±0.03 molH2 mol−1 hexose and hydrogen production rate from 4.4±0.38 to 6.1±0.03 lH2 l−1 POMEd−1 (OThong et al., 2007). In case of Rhodopseudomonas palustris PBUM001, the process parameters for the hydrogen production were optimized using response surface methodology (RSM). The maximum predicted cumulative hydrogen production and COD reduction of 1.05 ml H2/ml POME and 31.71% respectively were obtained based on the developed optimum conditions of 100% (v/v) POME concentration, 10% (v/v) inoculum size, light intensity of 4.0 klx, agitation rate of 250 rpm and pH of 6 (Jamil et al., 2009). Therefore, sustainable production of biohydrogen from POME could help in reducing the energy-linked environmental impacts, global warming due to anthropogenic carbon emissions and mobile source emissions such as carbon monoxide, nitrogen oxides, sulphur oxides, non-methane hydrocarbons, and particulates. Compost and Biofertilizer: Composting is a process whereby complex organic residues of plant and animal origins are converted into manure or biofertilizer (Singh et al., 2010) through the activities of several microbial systems (bacteria, actinomycetes, and fungi). This process helps in stabilizing various types of industrial wastes and sludge (e.g. sludge from pulp and paper, sugar, oleochemical, oil mills, etc.),and aids in reducing the volume/weight of the produced sludge (Abd-Rahman et al., 2003). Since POME is of biological origin, its composting can be a good alternative for its sustainable management. Though, oil palm empty fruit bunches (EFB) have been used to produce organic fertilizer and the process led to their bulk volume reduction by about 50%. (Chavalparit et al.,2006). Baharuddin et al. (2009) studied the physicochemical changes during co-composting of EFB with partially treated POME on a pilot scale. Initial rise in temperature was noticed during the first 3 days of treatment and thereafter the temperature fluctuated between 50o–62oC throughout the composting period. However, no much variation in moisture content from the initial values of 65–75% to about 60% at the end of the treatment, and the pH ranges from 7.75–8.10. Decrease in C/N ratio from 45 to 12 was identified after 60 days of composting. The macro and micronutrients are present in considerable amounts in the final compost. Thus, concluding that the utilization of EFB with POME for composting process can produce acceptable quality compost that can be applied to palm oil plantations as biofertilizer and for soil conditioning. Therefore, the production of compost using POME could serve as a valorization strategy that can reduce the volume of this waste with easy land application. Enzyme production: Hydrolytic enzymes are among the most important groups of industrial enzymes; because of their biotechnological potential use. According to technical market research report, enzymes for industrial applications is expected to increase to over $2.7 billion by 2012, with an average annual growth rate of 4%. The total industrial enzyme market in 2009 was reported to be $2.4 billion (Hassan et al., 2006). The POME has been reported to be utilized as a medium for industrial enzyme production by different microorganisms. White rot fungus Phanerochaete chrysosporium was used for lignin peroxidase production using POME as the main substrate in the presence of wheat flour as the co-substrate (Alam et al. 2006). Protease production by A. terreus IMI 282743 using pre-filtered POME yieldeda maximum activity of 129 U/ml after four days of fermentation in a medium containing 75% (v/v) retentate of pre-filtered POME at 37oC, 250 rpm and 5% (v/v) of temperature, agitation and inoculum concentration respectively (Wu et al., 2006). Based on this, Wu et al. (2009) explored the use of statistical experimental design to optimize the medium and process conditions. The developed optimum conditions of 37.95oC, 1.30% (v/v) and 3.83 days for temperature,

471 J. Appl. Sci. Res., 8(1): 466-473, 2012

inoculum concentration and fermentation time respectively resulted in 4.37-fold increase in extracellular protease production. Rashid et al. (2009) studied the production of cellulase in the presence of POME as a basal medium. The results revealed that T. reesei RUT C-30 resulted in the filter paper cellulase and carboxymethylcellulase activity of 0.917 U/ml and 2.51 U/ml respectively after 5 days of fermentation. Submerged and solid state fermentationswere used by Prasertsan et al. (1997) to optimize the cellulase (CMCase) and xylanase productions using A. niger ATCC 6275. Addition of 0.6 g/l NH4NO3 into the POME during the fermentation process increased the production of both xylanases and CMCases. The residual oil and grease present in POME could serve as inducers during the lipase production. Razak et al. (1997) isolated two fungal species (Rhizopus oryzae and Rhizopus rhizopodiformis) from POME that showed potentials to produce both themembrane-bound and extracellular lipases under appropriate conditions.Salihu et al. (2011a)utilized POME as a growth medium for lipase production in shake flask cultures using ten different microorganisms. All the strains showed considerable levels of lipase activity and the highest activity of 4.02 U/ml was found in Candida cylindracea ATCC 14830.The C. cylindracea lipase production was optimized by RSM and the optimum medium containing POME supplemented with 0.45% (w/v), 0.65% (v/v) and 0.2% (v/v) of peptone, Tween-80 and olive oil respectivelyresulted in highest lipase production of 20.26 U/ml (Salihu et al., 2011b). Conclusion: Agricultural residuesare produced in large quantities in many developing countries. Their use has still been limited, being basically used as feeds for animals, or simply as landfills. However, they can serve as potential resources for use in several bioconversion processes for producing valuable products. Numerous attempts have been made forusing POME in the production of value-added products, these help in solving pollution problems, which may be caused by its disposal. Also, realization of these potentials offered by POME can be of special economic interest for countries with abundant agro-industrial residues. As such, research interests have been inspired in establishing a selective, reliable and durable alternative for judicious utilization of the residues across the globe. References Abd-Rahman, R., K.S. Mohd and Y. Abu Zahrim, 2003. Composting palm oil mill sludge - sawdust: Effect of different amount of sawdust. Proceedings of National workshop in conjunction with ARRPET workshop on Wastewater treatment and recycling 2: Removal chloroorganics and heavy metals. ISBN 983-2982-04-9. Abdul Latif, A., I. Suzylawati, I. Norliza and B. Subhash, 2003a. Removal of suspended solids and residual oil from palm oil mill effluent.J. Chem. Technol. Biotechnol., 78(9): 971-978. Abdul Latif, A., I. Suzylawati, I. Norliza and B. Subhash, 2003b. Water recycling from palm oil mill effluent using membrane technology.Desalination, 157: 87-95. Ahmad, A., S. Ismail and S. Bhatia, 2003. Water recycling from palm oil mill effluent (POME) using membrane technology. Desalination, 157: 87-95. Ahmad, A.L., C.Y. Chan, S.R. AbdShukor and M.D. Mashitah, 2008. Recovery of oil and carotenes from palm oil mill effluent (POME).Chem. Engin. J., 141: 383-386. Ahmad, A.L., C.Y. Chan, S.R. AbdShukor and M.D. Mashitah, 2010. Optimization of carotene recovery from extracted oil of POME by adsorption chromatography using response surface methodology. Sep. Purif. Technol., 73: 279-285. Alam, M.Z., P. Jamal and M.M. Nadzir, 2008a. Bioconversion of palm oil mill effluent for citric acid production: statistical optimization of fermentation media and time by central composite design. World J. MicrobiolBiotechnol., 24: 1177-1185. Alam, M.Z., N.A. Kabbashi and K.H.M. Zain, 2008b. Optimization of Media Composition for Bioethanol Production by Direct Bioconversion of Palm Oil Mill Effluent, Proceedings of International Conference on Environmental Research and Technology (ICERT 2008), 952-956. Alam, M.Z., N.A. Kabbashi and A.A. Razak, 2007. Liquid State Bioconversion of Domestic Wastewater Sludge for Bioethanol Production, In Ibrahim, F., N. A. Abu Osman, J. Usman and N. A. Kadri (Eds.): Biomed 06, IFMBE Proceedings, 15: 479-482. Alam, M.Z., M.I. AbdulKarim and M.T. Mespuan, 2006. Statistical optimization of physicochemical factors for lignin peroxidase production using POME as substrate.Proceedings of the 20th Symposium of Malaysian Chemical Engineers (SomChE 2006). Shah Alam, Malaysia, pp: 151-156. Alam, M.Z., N.A. Kabbashi and S.N.I.S. Hussin, 2009. Production of bioethanol by direct bioconversion of oilpalm industrial effluent in a stirred-tank bioreactor.J. Ind. Microbiol. Biotechnol., 36: 801-808. Alias, Z. and I.K.P. Tan, 2005. Isolation of palm oil-utilising, polyhydroxyalkanoate (PHA)-producing bacteria by an enrichment technique.Bioresour. Technol., 96: 1229-1234.

472 J. Appl. Sci. Res., 8(1): 466-473, 2012

Baharuddin, A.S., M. Wakisaka, Y. Shirai, S. Abd Aziz, N.A. Abdul Rahman and M.A. Hassan, 2009. Cocomposting of empty fruit bunches and partially treated palm oil mill effluents in pilot scale. Int. J. Agric. Res., 4(2): 69-78. Basiron, Y. and C.K. Weng, 2004. The oil palm and its sustainability.J. Oil Palm Res., 16(1): 1-10. Chan, K.S. and C.F. Chooi, 1984. Ponding System for palm oil mill effluent treatment. In: Proceedings of the Regional Workshop on Palm Oil Mill Technology & Effluent Treatment, 185-192. Chavalparit, O., W.H. Rulkens, A.P.J. Mol and S. Khaodhair, 2006. Options for environmental sustainability of the crude palm oil industry in Thailand through enhancement of industrial ecosystems. Environ. Dev. Sustain., 8: 271-287. Cheng, C.K., H.H. Hani and K.S.K. Ismail, 2007. Production of bioethanol from oil palm empty fruit bunches. International Conference on Sustainable Materials (ICoSM-2007), 69-72. Cheung, S.M. and B.C. Anderson, 1996. Laboratory investigation of ethanol production from municipal primary wastewater solids.Bioresour. Technol., 59: 81-96. Chong, M., N.A. Abdul Rahman, R. Abdul Rahim, S. Abdul Aziz, Y. Shirai and M.A. Hassan, 2009. Optimization of biohydrogen production by Clostridium butyricum EB6 from palm oil mill effluent using response surface methodology.Int. J. Hydrogen Energy, 34: 7475-7482. Choorit, W. and P. Wisarnwan, 2007. Effect of temperature on the anaerobic digestion of palm oil mill effluent.Electr. J. Biotechnol., 10(3): 376-385. Drysdale, C.R. and M.H. McKay, 1995. Citric acid production by Aspergillus niger on surface culture on inulin. Lett. Appl. Microbiol., 20: 252-254. Foo, K.Y. and B.H. Hameed, 2010. Insight into the applications of palm oil mill effluent: A renewable utilization of the industrial agricultural waste. Renew. Sustain. Energy Rev., 14: 1445-1452. Grewal, H.S. and A.L. Karla, 1995. Fungal production of citric acid.Biotechnol. Adv., 13: 209-234. Gupta, S., 1994. Continuous production of citric acid from sugar cane molasses using a combination of submerged immobilized and surface stabilized cultures of Aspergillus niger KCU520. Biotechnol. Lett., 16: 599-604. Gutiérrez, L.F., O.J. Sánchez and C.A. Cardona, 2009. Process integration possibilities for biodiesel production from palm oil using ethanol obtained from lignocellulosic residues of oil palm industry.Bioresour. Technol., 100(3): 1227-1237. Habib, M.A.B., F.M. Yusoff, S.M. Phang, K.J. Ang and S. Mohamed, 1997. Nutritional values of chironomid larvae grown in palm oil mill effluent and algal culture. Aquaculture, 158: 95-105. Hahn-Hagerdal, B., M. Galbe, M.F. Gorwa-Grauslund, G. Lidenand, G. Zacchi, 2006. Bio-ethanol: the fuel of tomorrow from the residues of today. Trends Biotechnol., 24(12): 549-556. Hasan, F., A.A. Shah and A. Hameed, 2006. Industrial applications of microbial lipases.Enzym. Microbial Technol., 39: 235-251. Hassan, M.A., Y. Shirai, N. Kusubayashi, M.I. Abdulkarim, K. Nakanishi and K. Hashimoto, 1996. Effect of Organic acid profiles during Anaerobic Treatment of Palm Oil Mill Effluent on the Production of Polyhydroxyalkanoates by Rhodobactersphaeroides. J. Ferment. Bioengin., 82(2): 151-156. Jamal, P., M.Z. Alam, M.R.M. Salleh and M.M. Akib, 2005. Sewage Treatment Plant Sludge: A Source of Potential Microorganism for Citric acid Production, American J. Appl. Sci., 2(8): 1236-1239. Jamal, P., M.Z. Alam and A. Mohamad, 2007. Microbial Bioconversion of Palm Oil Mill Effluent to Citric Acid with Optimum Process Conditions, In: Ibrahim, F., N.A. Abu Osman, J. Usman and N.A. Kadri (Eds.): Biomed 06, IFMBE Proceedings, 15: 483-487. Jamil, Z., M.S.M. Annuar, S. Ibrahim and S. Vikineswary, 2009. Optimization of phototrophic hydrogen production by Rhodopseudomonas palustris PBUM001 via statistical experimental design.Int. J. Hydrogen Energy, 34: 7502-7512. Kathiravale, S. and A. Ripin, 1997. Palm oil mill effluent treatment towards zero discharge, A paper presented at National Science and Technology Conference, Kuala Lampur, Malaysia (July, 15th -16th 1997), 1-8. Ma, A.N., 1999. Treatment of palm oil mill effluent. In: Gurmit, S., et al. (Eds.). Oil Palm and the Environment.A Malaysian Perspective. MOPGC, Kuala Lumpur, 113-125. Mumtaz, T., N.A. Yahaya, S. Abd-aziz, N. AbdulRahman, P.L. Yee, Y. Shirai and M.A. Hassan, 2010. Turning waste to wealth biodegradable plastics polyhydroxyalkanoates from palm oil mill effluent – a Malaysian perspective.J. Clean. Prod., 18(14): 1393-1402. Najafpour, G.D., A.A.L. Zinatizadeh, A.R. Mohamed, M.H. Isa and H. Nasrollahzadeh, 2006. High-rate anaerobic digestion of palm oil mill effluent in an upflow anaerobic sludge-fixed film bioreactor.Process Biochem., 41(2): 370-379. Oswal, N., P.M. Sarma, S.S. Zinjarde and A. Pant, 2002. Palm oil mill effluent treatment by a tropical marine yeast. Bioresour. Technol., 85: 35-37. O-Thong, S., P. Prasertsan, N. Intrasungkha, S. Dhamwichukorn and N. Birkeland, 2007. Improvement of biohydrogen production and treatment efficiency on palm oil mill effluent with nutrient supplementation at

473 J. Appl. Sci. Res., 8(1): 466-473, 2012

thermophilic condition using an anaerobic sequencing batch reactor.Enzym.Microb. Technol., 41: 583590. Poh, P.E. and M.F. Chong, 2009. Development of anaerobic digestion methods for palm oil mill effluent (POME) treatment.Bioresour. Technol., 100: 1-9. Prasertsan, P., A.H. Kittikul, A. Kunghae, J. Maneesri and S. Oi, 1997. Optimization for xylanase and cellulase production from Aspergillus niger ATTC 6275 in palm oil mill wastes and its application. World J. Microbiol.Biotechnol., 13: 555-559. Purushothaman, M., R.K.I. Anderson, S. Narayana and V.K. Jayaraman, 2001. Industrial byproducts as cheaper medium components influencing the production of Polyhydroxyalkanoates (PHA) – Biodegradable Plastics. Bioprocess Biosys. Engin., 24: 131-136. Rashid, S.S., M.Z. Alam, M.A. Abdulkarim and M.H. Salleh, 2009. Management of palm oil mill effluent through production of cellulases by filamentous fungi.World J Microbiol.Biotechnol., 25(12): 2219-2226. Rass-Hansen, J., H. Falsig, B. Jorgensen and C.H. Christensen, 2007. Perspective bioethanol: fuel or feedstock? J. Chem. Technol Biotechnol., 82: 329-333. Razak, C.N.A., A.B. Salleh, R. Musani, M.Y. Samad and M. Basri, 1997. Some characteristics of lipases from thermophilic fungi isolated from palm oil mill effluent. J. Mol. Catal. B: Enzym., 3: 153-159. Redzwan, G., S.N. Gan and I.K.P. Tan, 1997. Short Communication: Isolation of polyhydroxyalkanoateproducing bacteria from an integrated-farming pond and palm-oil mill effluent ponds. World J. Microbiol.Biotechnol., 13: 707-709. Roukas, T. and P. Kotzekidou, 1997. Pretreatment of Date syrup to increase Citric acid Production. Enzym.Microb. Technol., 21: 273-276. Salihu, A., M.Z. Alam, M.I. AbdulKarim and H.M. Salleh, 2011a. Suitability of using Palm oil mill effluent as a medium for lipase production.Afr. J. Biotechnol., 10(11): 2044-2052. Salihu, A., M.Z. Alam, M.I. AbdulKarim and H.M. Salleh, 2011b. Optimization of lipase production by Candida cylindracea in palm oil mill effluent based medium using statistical experimental design. J. Mol. Catal. B: Enzym., 69: 66-73. Singh, R.P., M.H. Ibrahim, N. Esa and M.S. Iliyana, 2010. Composting of waste from palm oil mill: a sustainable waste management practice.Rev. Environ. Sci. Biotechnol., 9: 331-344. Vairappan, S.C. and A.M. Yen, 2008. Palm oil mill effluent (POME) cultured marine microalgae as supplementary diet for rotifer culture. J. Appl. Phycol., 20: 603-608. Vijayaraghavan, K., D. Ahmad and M.E. Abdul Aziz, 2007. Aerobic treatment of Palm oil mill effluent. J. Environ. Man., 82: 24-31. Vikineswary, S., A.J. Kuthubutheen and A.A. Ravoof, 1997. Growth of Trichoderma harzianum and Myceliophthora thermophila in palm oil sludge.World J. Microbiol.Biotechnol., 13: 189-194. Wahid, M.D., S.N.A. Abdullah and I.E. Henson, 2004. Oil Palm - Achievements and Potential: 2004 new directions for a diverse planet. Proceedings of the 4th International Crop Science Congress (26th Sep – 1st Oct). Brisbane, Australia. Wingren, A., M. Galbe and G. Zacchi, 2003. Techno-economic evaluation of producing ethanol from softwood: comparison of SSF and SHF and identification of bottlenecks. Biotechnol.Prog., 19: 1109-1117. Wu, T.Y., A.W. Mohammad, J.M. Jahim and N. Anuar, 2006. Investigations on protease production by a wildtype Aspergillus terreus strain using diluted retentate of pre-filtered palm oil mill effluent (POME) as substrate. Enzym.Microb. Technol., 39: 1223-1229. Wu, T.Y., A.W. Mohammad, J.M. Jahim and N. Anuar, 2009. Optimized reuse and bioconversion from retentate of pre-filtered palm oil mill effluent (POME) into microbial protease by Aspergillus terreus using response surface methodology. J Chem. Technol. Biotechnol., 84: 1390-1396. Wyman, C.E., 1996. Ethanol production from lignocellulosic biomass: overview. In: Wyman, C. E. (ed.). Handbook on Bioethanol: Production and Utilization. Taylor and Francis, Washington, pp: 1-18. Yusoff, S. and S.B. Hansen, 2007. Feasibility Study of Performing an Life Cycle Assessment on Crude Palm Oil Production in Malaysia. Int. J. Life Cycle Assess, 12(1): 50-58.