A holistic approach to managing palm oil mill effluent (POME): biotechnological advances in the sustainable reuse of POME

During the last century, a great deal of research and development as well as applications has been devoted to waste. These include waste minimization and treatment, the environmental assessment of waste, minimization of environmental impact, life cycle assessment and others. The major reason for such huge efforts is that waste generation constitutes one of the major environmental problems where production industries are concerned. Until now, an increasing pressure has been put on finding methods of reusing waste, for instance through cleaner production, thus mirroring rapid changes in environmental policies. The palm oil industry is one of the leading industries in Malaysia with a yearly production of more than 13 million tons of crude palm oil and plantations covering 11% of the Malaysian land area. However, the production of such amounts of crude palm oil result in even larger amounts of palm oil mill effluent (POME), estimated at nearly three times the quantity of crude palm oil. Normally, POME is treated using end-of-pipe processes, but it is worth considering the potential value of POME prior to its treatment through introduction of a cleaner production. It is envisaged that POME can be sustainably reused as a fermentation substrate in the production of various metabolites, fertilizers and animal feeds through biotechnological advances. The present paper thus discusses various technically feasible and economically beneficial means of transforming the POME into low or preferably high value added products.     

Performance and microbial diversity of palm oil mill effluent microbial fuel cell

Aim: To evaluate the bioenergy generation and the microbial community structure from palm oil mill effluent using microbial fuel cell. Methods and Results: Microbial fuel cells enriched with palm oil mill effluent (POME) were employed to harvest bioenergy from both artificial wastewater containing acetate and complex POME. The microbial fuel cell (MFC) showed maximum power density of 3004 mW m^?2 after continuous feeding with artificial wastewater containing acetate substrate. Subsequent replacement of the acetate substrate with complex substrate of POME recorded maximum power density of 622 mW m^?2. Based on 16S rDNA analyses, relatively higher abundance of Deltaproteobacteria (88·5%) was detected in the MFCs fed with acetate artificial wastewater as compared to POME. Meanwhile, members of Gammaproteobacteria, Epsilonproteobacteria and Betaproteobacteria codominated the microbial consortium of the MFC fed with POME with 21, 20 and 18·5% abundances, respectively. Conclusions: Enriched electrochemically active bacteria originated from POME demonstrated potential to generate bioenergy from both acetate and complex POME substrates. Further improvements including the development of MFC systems that are able to utilize both fermentative and nonfermentative substrates in POME are needed to maximize the bioenergy generation. Significance and Impact of the Study: A better understanding of microbial structure is critical for bioenergy generation from POME using MFC. Data obtained in this study improve our understanding of microbial community structure in conversion of POME to electricity.     

Evaluation of methods for preparing hydrogen-producing seed inocula under thermophilic condition by process performance and microbial community analysis

Five methods for preparation of hydrogen-producing seeds (base, acid, 2-bromoethanesulfonic acid (BESA), load-shock and heat shock treatments) as well as an untreated anaerobic digested sludge were compared for their hydrogen production performance and responsible microbial community structures under thermophilic condition (60 degrees C). The results showed that the load-shock treatment method was the best for enriching thermophilic hydrogen-producing seeds from mixed anaerobic cultures as it completely repressed methanogenic activity and gave the a maximum hydrogen production yield of 1.96 mol H(2) mol(-1) hexose with an hydrogen production rate of 11.2 mmol H(2) l(-1)h(-1). Load-shock and heat-shock treatments resulted in a dominance of Thermoanaerobacterium thermosaccharolyticum with acetic acid and butyric acid type of fermentation while base- and acid-treated seeds were dominated by Clostridium sp. and BESA-treated seeds were dominated by Bacillus sp. The comparative experimental results from hydrogen production performance and microbial community analysis showed that the load-shock treatment method was better than the other four methods for enriching thermophilic hydrogen-producing seeds from anaerobic digested sludge. Load-shock treated sludge was implemented in palm oil mill effluent (POME) fermentation and was found to give maximum hydrogen production rates of 13.34 mmol H(2) l(-1)h(-1) and resulted in a dominance of Thermoanaerobacterium spp. Load-shock treatment is an easy and practical method for enriching thermophilic hydrogen-producing bacteria from anaerobic digested sludge.     

Composting of waste from palm oil mill: a sustainable waste management practice

Malaysia is blessed with abundant natural resources and bears a favorable climate for commercial cultivation of crops such as oil palm. In Malaysia the total plantation area of oil palm was 4,487,957 ha in 2008. It has been reported that in 2005 there was a total of 423 palm oil mills having production capacity of approximately 89 million tonnes of fresh fruit bunch (FFB) per year. Waste from the oil palm mill process include palm oil mill effluent (POME), generated mainly from oil extraction, washing and cleaning up processes. POME contains cellulosic material, fat, oil, and grease. Discharging untreated effluent into water streams may cause considerable environmental problems. The solid wastes generated are mainly decanter cake, empty fruit bunches, seed shells and fibre from the mesocarp. POME as well as the solid wastes may rapidly deteriorate the surrounding environment if not dealt with properly. Hence there is an urgent need for a sustainable waste management system to tackle these wastes. As these wastes are organic in origin, they are rich in plant nutrients. Composting of waste generated from palm oil mills can be good practice as it will be helpful in recycling useful plant nutrients. This review deals with various aspects of waste management practices in palm oil mills and the possibility of composting the wastes.     

Suppression of filamentation in recombinant Escherichia coli by amplified FtsZ activity

A stable plasmid pSYL107 containing the Alcaligenes eutrophus polyhydroxyalkanoate biosynthesis genes and the Escherichia coli ftsZ gene was constructed. Cell filamentation previously observed during the synthesis of poly(3-hydroxybutyric acid), PHB, could be suppressed by the amplified activity of FtsZ. In a defined medium XL1-Blue (pSYL107) accumulated twice as much PHB than XL1-Blue harboring pSYL105, which does not contain the ftsZ gene.     

Renewable and sustainable bioenergies production from palm oil mill effluent (POME): win-win strategies toward better environmental protection

Palm oil industry is one of the leading agricultural industries in Malaysia with average crude palm oil production of more than 13 million tonne per year. However, production of such huge amount of crude palm oil has consequently resulted to even larger amount of palm oil mill effluent (POME). POME is a highly polluting wastewater with high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) in which can caused severe pollution to the environment, typically pollution to water resources. On the other hand, POME was identified as a potential source to generate renewable bioenergies such as biomethane and biohydrogen through anaerobic digestion. In other words, a combination of wastewater treatment and renewable bioenergies production would be an added advantage to the palm oil industry. In line with the world's focus on sustainability concept, such strategy should be implemented immediately to ensure palm oil is produced in an environmental friendly and sustainable manner. This review aims to discuss various technologies to convert POME to biomethane and biohydrogen in a commercial scale. Furthermore, discussion on using POME to culture microalgae for biodiesel and bioethanol production was included in the present paper as a new remedy to utilize POME with a greater beneficial return.     

Efficient production of polyhydroxyalkanoates from plant oils by Alcaligenes eutrophus and its recombinant strain

The ability of Alcaligenes eutrophus to grow and produce polyhydroxyalkanoates (PHA) on plant oils was evaluated. When olive oil, corn oil, or palm oil was fed as a sole carbon source, the wild-type strain of A. eutrophus grew well and accumulated poly(3-hydroxybutyrate) homopolymer up to approximately 80% (w/w) of the cell dry weight during its stationary growth phase. In addition, a recombinant strain of A. eutrophus PHB⁻4 (a PHA-negative mutant), harboring a PHA synthase gene from Aeromonas caviae, was revealed to produce a random copolyester of 3-hydroxybutyrate and 3-hydroxyhexanoate from these plant oils with a high cellular content (approximately 80% w/w). The mole fraction of 3-hydroxyhexanoate units was 4–5 mol% whatever the structure of the triglycerides fed. The polyesters produced by the A. eutrophus strains from olive oil were 200–400 kDa (the number-average molecular mass). The results demonstrate that renewable and inexpensive plant oils are excellent carbon sources for efficient production of PHA using A. eutrophus strains. Received: 3 September 1997 / Received revision: 10 November 1997 / Accepted: 16 November 1997     

Polyhydroxyalkanoate production from anaerobically treated palm oil mill effluent by new bacterial strain <Emphasis Type="Italic">Comamonas</Emphasis> sp. EB172

A new isolate designated as strain EB172 was isolated from a digester treating palm oil mill effluent and was investigated by polyphasic taxonomic approach. The cells were rod-shaped, Gram-negative, non-pigmented, non-spore-forming and non-fermentative. Phylogenetic analysis using the 16S rRNA gene sequence showed that the strain clustered with the genus Comamonas. Its closest neighbours were the type strains Comamonas terrigena (96.8%), Comamonas koreensis (93.4%), Comamonas composti (92.9%), and Comamonas kerstersii (91.1%). The ability of the strain EB172 to produce polyhydroxyalkanoates (PHA) when supplied with organic acids made this bacterium unique among Comamonas species. The bacterial strain was clearly distinguished from all of the existing strains by phylogenetic analysis, fatty acid composition and a range of physiological and biochemical characteristics. The G+C content of the genomic DNA was 59.1 mol%. The strain showed good growth in acetic, propionic and n-butyric acids. Comamonas sp. EB172 produced 9.8 g/l of cell dry weight and accumulated 59 (wt%) of PHAs when supplemented with mixed organic acids from anaerobically treated palm oil mill effluent. It is evident from the genotypic, phenotypic data and ability to produce PHAs that strain EB172 represents a new strain in the genus Comamonas (GeneBank accession no. EU847238).     

Fermentative production of poly-β-hydroxybutyric acid from xylose by a two-stage culture method employing Lactococcus lactis IO-1 and Alcaligenes eutrophus

Summary A two-stage culture method employing Lactococcus.lactis IO-1 and Alcaligenes eutrophus was developed for production of poly--hydroxybutyric acid (PHB) from xylose. In this method, xylose was converted to L-lactic acid and acetic acid by L.lactis IO-1, and then the organic acids were converted to PHB by A.eutrophus. When the supernatant of the IO-1 culture broth, containing 10 g·dm^-3 L-lactate derived from xylose, was used as medium for A. eutrophus, the concentration of cells increased to 8.5 g·dm^-3 in 24 h and 55% of the content in the cells by weight was PHB.     

Management of palm oil mill effluent through production of cellulases by filamentous fungi

A laboratory scale study to evaluate the potentiality of filamentous fungi for the production of cellulolytic enzymes using palm oil mill effluent (POME) as a basal medium was initiated. A total of 25 filamentous fungi in which 16 filamentous fungi were isolated and purified from oil palm industrial residues and 9 strains from laboratory stock were screened using POME with 1% total suspended solids. Trichoderma reesei RUT C-30 was identified as a potential strain for cellulolytic enzyme production as compared to other genera of Aspergillus, Penicillum, Rhizopus, Phanerochaete, Trichoderma and basidiomycete groups. The results showed that T. reesei RUT C-30 gave the highest filter paper cellulase and carboxy methyl cellulase activity of 0.917 and 2.51 U/ml respectively at day 5 of fermentation. Other parameters such as growth formation, pH, filterability and total biosolids were observed to evaluate the bioconversion process.     

Aerobic granular sludge formation for high strength agro-based wastewater treatment

The present study investigates the formation of aerobic granular sludge in sequencing batch reactor (SBR) fed with palm oil mill effluent (POME). Stable granules were observed in the reactor with diameters between 2.0 and 4.0 mm at a chemical oxygen demand (COD) loading rate of 2.5 kg COD m⁻³ d⁻¹. The biomass concentration was 7600 mg L⁻¹ while the sludge volume index (SVI) was 31.3 mL g SS⁻¹ indicating good biomass accumulation in the reactor and good settling properties of granular sludge, respectively. COD and ammonia removals were achieved at a maximum of 91.1% and 97.6%, respectively while color removal averaged at only 38%. This study provides insights on the development and the capabilities of aerobic granular sludge in POME treatment.     

Dairy manure pellets and palm oil mill effluent as alternative nutrient sources in cultivating Sporosarcina pasteurii for calcium carbonate bioprecipitation

Microbially induced carbonate precipitation (MICP) is a process that hydrolysis urea by microbial urease to fill the pore spaces of soil with induced calcium carbonate (CaCO₃) precipitates, which eventually results in improved or solidified soil. This research explored the possibility of using dairy manure pellets (DMP) and palm oil mill effluent (POME) as alternative nutrient sources for Sporosarcina pasteurii cultivation and CaCO₃ bioprecipitation. Different concentrations (20–80 g l⁻¹) of DMP and POME were used to propagate the cells of S. pasteurii under laboratory conditions. The measured CaCO₃ contents for MICP soil specimens that were treated with bacterial cultures grown in DMP medium (60%, w/v) was 15·30 ± 0·04 g ml⁻¹ and POME medium (40%, v/v) was 15·49 ± 0·05 g ml⁻¹ after 21 days curing. The scanning electron microscopy showed that soil treated with DMP had rhombohedral structure-like crystals with smooth surfaces, whilst that of POME entailed ring-like cubical formation with rough surfaces Electron dispersive X-ray analysis was able to identify a high mass percentage of chemical element compositions (Ca, C and O), whilst spectrum from Fourier-transform infrared spectroscopy confirmed the vibration peak intensities for CaCO₃. Atomic force microscopy further showed clear topographical differences on the crystal surface structures that were formed around the MICP treated soil samples. These nutrient sources (DMP and POME) showed encouraging potential cultivation mediums to address high costs related to bacterial cultivation and biocementation treatment.     

Production of biodegradable copolyesters of 3-hydroxybutyrate and 4-hydroxybutyrate by Alcaligenes eutrophus

Summary New copolyesters of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) were produced by Alcaligenes eutrophus from various carbon sources of 4-hydroxybutyric acid, 4-chlorobutyric acid, 1,4-butanediol, and -butyrolactone. The composition of copolyesters varied from 0 to 37 mol% 4HB, depending on the carbon sources supplied. The biosynthetic pathway of copolyesters has been discussed. The copolyester film was biodegradable in soil and activated sludge. The rate of biodegradation was enhanced by the presence of 4HB units.     

Manipulation of the genes for poly-β-hydroxybutyric acid synthesis in Alcaligenes eutrophus

Summary In order to establish the molecular breeding system in Alcaligenes eutrophus producing poly--hydroxybutyric acid (PHB), phbCAB genes from A. eutrophus were recombined into the E. coli-A. eutrophus shuttle vector and directly transferred into A. eutrophus by the electroporation. In A. eutrophus transformants, recombinant plasmids were stably maintained and enzyme activities for PHB biosyntheses were elevated 1.4–2.7 fold by the cloned genes.     

Isolation of palm oil-utilising, polyhydroxyalkanoate (PHA)-producing bacteria by an enrichment technique

In early attempts to isolate palm oil-utilising bacteria from palm oil mill effluent (POME), diluted liquid samples of POME were spread on agar containing POME as primary nutrient. 45 purified colonies were screened for intracellular lipids by staining with Sudan Black B. Of these, 10 isolates were positively stained. The latter were grown in a nitrogen-limiting medium with palm olein (a triglyceride) or saponified palm olein (salts of fatty acids) as carbon source. None of the isolates grew in the palm olein medium but all grew well in the saponified palm olein medium. Of the latter however, only one isolate was positively stained with Nile Blue A, indicating the presence of PHA. This method did not successfully generate bacterial isolates which could metabolise palm olein to produce PHA. An enrichment technique was therefore developed whereby a selective medium was designed. The latter comprised minerals and palm olein (1% w/v) as sole carbon source to which POME (2.5% v/v) was added as the source of bacteria. The culture was incubated with shaking at 30 degrees C for 4 weeks. Out of seven isolates obtained from the selective medium, two isolates, FLP1 and FLP2, could utilise palm olein for growth and production of the homopolyester, poly(3-hydroxybutyrate). FLP1 is gram-negative and is identified (BIOLOG) to have 80% similarity to Burkholderia cepacia. When grown with propionate or valerate, FLP1 produced a copolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate).     

Comparison of different treatment options for palm oil production waste on a life cycle basis

Background, aim, and scope  

Globally, 45 million metric tonnes of palm oil has been produced in 2009. The production of 1 t crude palm oil requires 5 t of fresh fruit bunches (FFB). On average, processing of 1 t FFB in palm oil mills generates 230 kg empty fruit bunches (EFB) and 650 kg palm oil mill effluent (POME) as residues. These residues cause considerable environmental burdens, particularly greenhouse gas emissions. In order to reduce those emissions, four waste management options are compared in the present study using 1,000 kg of FFB as functional unit.     

Transfer and expression of PCB-degradative genes into heavy metal resistantAlcaligenes eutrophus strains

Sites polluted with organic compounds frequently contain inorganic pollutants such as heavy metals. The latter might inhibit the biodegradation of the organics and impair bioremediation. Chromosomally located polychlorinated biphenyl (PCB) catabolic genes ofAlcaligenes eutrophus A5,Achromobacter sp. LBS1C1 andAlcaligenes denitrificans JB1 were introduced into the heavy metal resistantAlcaligenes eutrophus strain CH34 and related strains by means of natural conjugation. Mobile elements containing the PCB catabolic genes were transferred fromA. eutrophus A5 andAchromobacter sp. LB51C1 intoA. eutrophus CH34 after transposition onto their endogenous IncP plasmids pSS50 and pSS60, respectively. The PCB catabolic genes ofA. denitrificans JB1 were transferred intoA. eutrophus CH34 by means of RP4::Mu3A mediated prime plasmid formation. TheA. eutrophus CH34 transconjugant strains expressed both catabolic and metal resistance markers. Such constructs may be useful for the decontamination of sites polluted by both organics and heavy metals.     

Biosynthesis of copolyesters consisting of 3-hydroxybutyric acid and medium-chain-length 3-hydroxyalkanoic acids from 1,3-butanediol or from 3-hydroxybutyrate by Pseudomonas sp. A33

Pseudomonas sp. A33 and other isolates of aerobic bacteria accumulated a complex copolyester containing 3-hydroxybutyric acid (3HB) and various medium-chain-length 3-hydroxyalkanoic acids (3HA_MCL) from 3-hydroxybutyric acid or from 1,3-butanediol under nitrogen-limitated culture conditions. 3HB contributed to 15.1 mol/100 mol of the constituents of the polyester depending on the strain and on the cultivation conditions. The accumulated polymer was a copolyester of 3HB and 3HA_MCL rather than a blend of poly(3HB) and poly(3HA_MCL) on the basis of multiple evidence. 3-Hydroxyhexadecenoic acid and 3-hydroxyhexadecanoic acid were detected as constituents of polyhydroxyalkanoates, which have hitherto not been described, by¹³C nuclear magnetic resonance or by gas chromatography/mass spectrometric analysis. In total, ten different constituents were detected in the polymer synthesized from 1,3-butanediol by Pseudomonas sp. A33:besides seven saturated (3HB, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate, and 3-hydrohexadecanoate) three unsaturated (3-hydroxydodecenoate, 3-hydroxytetradecenoate and 3-hydrohexadecanoate) hydroxyalkanoic acid constituents occured. The polyhydroxyalkanoate synthase of Pseudomonas sp. A33 was cloned, and its substrate specificity was evaluated by heterologous expression in various strains of P. putida, P. oleovorans and Alcaligenes eutrophus.     

Bioconversion of palm oil mill effluent for citric acid production: statistical optimization of fermentation media and time by central composite design

A laboratory-scale study was conducted to evaluate the feasibility of using palm oil mill effluent (POME) as a major substrate and other nutrients for maximum production of citric acid using the potential fungal strain Aspergillus niger (A103). Statistical optimization of medium composition (substrate–POME, co-substrates–wheat flour and glucose, and nitrogen source–ammonium nitrate) and fermentation time was carried out by central composite design (CCD) to develop a polynomial regression model through the effects of linear, quadratic, and interaction of the factors. The statistical analysis of the results showed that, in the range studied, ammonium nitrate had no significant effect whereas substrate, co-substrates and fermentation time had significant effects on citric acid production. The optimized medium containing 2% (w/w) of substrate concentration (POME), 4% (w/w) of wheat flour concentration, 4% (w/w) of glucose concentration, 0% (w/v) of ammonium nitrate and 5 days fermentation time gave the maximum predicted citric acid of 5.37 g/l which was found to be 1.5 g/l in the experimental run. The determination of coefficient (R ²) from the analysis observed was 0.964, indicating a satisfactory adjustment of the model with the response. The analysis showed that the major substrate POME (P < 0.05), glucose (P < 0.01), nutrient (P < 0.05), and fermentation time (P < 0.01) was more significant for citric acid production. The bioconversion of POME for citric acid production using optimal conditions showed the higher removal of chemical oxygen demand (82%) with the production of citric acid (5.2 g/l) on the final day of fermentation process (7 days). The pH and biosolids accumulation were observed during the bioconversion process.     

The lysis of gram-negative Alcaligenes eutrophus and Alcaligenes latus by palmitoyl carnitine

Summary The use of synthetic palmitoyl carnitine, naturally occurring in cellular membranes, was investigated for the lysis of Alcaligenes eutrophus and Alcaligenes latus. The optimal concentration of the lysin was 1.0 mM and the lysis was almost completed in 60 minutes. Alcaligenes latus was more susceptible to the lytic activity of palmitoyl carnitine than Alcaligenes eutrophus. Palmitoyl carnitine was found to be a more effective lysin than lysozyme.