Category Archives: InPress

THE COLD FLOW PROPERTIES OF PALM BIODIESEL FOR DIESEL BLENDS MANDATE IN MALAYSIA’S HIGHLANDS

Greenhouse gas emission from burnt fossil fuels in transportation leads to global warming. Therefore, biodiesel which is believed to help in reducing carbon dioxide (CO2) emission has been widely used as renewable energy that will replace diesel fuel. Biodiesel of 7% in diesel or B7 has been accepted worldwide to be the automotive fuel. In the last decade, most countries that implemented biodiesel program have gradually increased its biodiesel blending ratio above 7% for economic and environmental reasons. Malaysia has also announced the implementation of B20 starting January 2020. However, the biodiesel mandate in Malaysia’s highlands was maintained at B7 because of the concern on low temperature vehicle operability. This study focuses on the cold flow properties of the blended diesel fuels and the quality of the palm biodiesel for the national biodiesel program. The monoglycerides and the water content in the biodiesel were evaluated in relation to cold temperature fuel performance. Cloud point (CP) and cold filter plugging point (CFPP) of B7 diesel sold at highlands were found below the lowest ambient temperature recorded at highlands for the past 10 years. Both CP and CFPP of Euro 5 diesel were lower than Euro 2M diesel. A 41-months survey of the monoglycerides and the water contents in the palm biodiesel indicated that the palm biodiesel used in Malaysia’s biodiesel mandate meets both the EN14214:2019 and the Malaysian Standard MS2008:2014 specifications. CP and CFPP of the blended fuels increase with the increase of biodiesel blending ratio. Based on the study, it is anticipated that B20 could be introduced at Malaysia’s highlands without any problem.

OIL PALM ECONOMIC PERFORMANCE IN MALAYSIA AND R&D PROGRESS IN 2020

The year 2020 faced unprecedented challenge for most of the global economic growth due to the outbreak of Coronavirus disease (COVID-19). Despite a downward trend performance of the Malaysian oil palm industry, particularly for the first half of 2020, the impact is less severe due to the encouraging palm oil export revenue through the National Economic Recovery Plan (PENJANA) which nurtures a notable increase in crude palm oil (CPO) price. In honouring the Malaysian pledge on forest conservation, land expansion for the oil palm cultivation remains stagnant over the years. The effort is now shifting towards enhancing the oil palm yield performance through new planting materials and good agricultural practices, coupled with systematic pest and disease management. Sustainability continues to be the key agenda of the oil palm industry, in moving forward to sustain the industry ecosystem. The industry is now open for innovative palm oil processes to comply with the dynamic and stringent food safety and quality standards and trade regulations. Owing to the distinction in food and feed applicability together with health prospects, translating the information into consumer-friendly language is becoming crucial for effective communication. Valorisation via the concept of ‘waste to wealth’ has compelled series of innovations in capitalising oil palm co-products for greener bioenergy and oleochemicals, and source of phytonutrients to generate higher earnings without having to heavily rely on palm oil trade as commodity. Mandatory enactment of the Malaysian Sustainable Palm Oil (MSPO) certification scheme has portrayed a success story of showing the utmost commitment towards sustainability. With persistent dedication, the oil palm industry is envisaged to be self-sustaining, amidst the never-ending challenges surrounding economy, well-being and environment.

CORRELATION BETWEEN NON-RIBOSOMAL PEPTIDE SYNTHETASE (NRPS) PRODUCTION AND VIRULENCE OF Ganoderma boninense PER71 ON OIL PALM (Elaeis guineensis)

Basal stem rot (BSR) disease caused by the white rot fungus Ganoderma boninense is the most destructive oil palm disease leading to production losses in fresh fruit bunches. Non-ribosomal peptide synthetase (NRPS) plays an important role in fungal pathogenicity. These large multi-modular enzymes catalyse the biosynthesis of secondary metabolites that act as fungal virulence factors. In this study, the detection of NRPS in G. boninense was achieved using polymerase chain reaction (PCR)-based method. Core motifs of adenylation domain of NRPS gene was identified in G. boninense. The deduced amino acid sequence showed similarity to the conserved core motifs (A2, A3 and A5) of the adenylation domain. Siderophores were predicted as the potential secondary metabolites synthesised by NRPS. Expression analysis of GbNRPS in 3-month-old oil palm artificially infected with G. boninense has confirmed the upregulation of GbNRPS at 1 month after inoculation (MAI) peaking at 4 MAI in susceptible clone but not in tolerant clone. There was a correlation between GbNRPS gene expression and disease severity. Susceptible clones showed significantly higher disease severity index (DSI) (62.50%) compared to tolerant clones (28.13%) at 4 MAI. This is the first putative detection of adenylation domain of NRPS (GbNRPS) gene and functional analysis of NRPS as a virulence factor in disease development.

STABILITY AND PERFORMANCE OF PALMBASED TRANSPARENT SOAP WITH OIL PALM LEAVES EXTRACT

Oil palm leaves (OPAL) is one of the oil palm waste components that can be extracted for natural phenolics. The OPAL extracts have been successfully extracted via four different extraction procedures; extraction with ethanol (OPAL M1), deoiled and followed by extraction with ethanol (OPAL M2), deoiled and extraction with ethanolic hydrochloric acid (OPAL M3) and aqueous extraction (OPAL M4). In this study, pH, moisture content, hardness, foaming power and stability, antioxidant activity and colour stability of transparent soaps with OPAL extracts were carried out. The results indicated that all transparent soaps with OPAL extracts had similar pH in the range of 9.88 to 9.98. However, there was a significant reduction of moisture content (14.6%-16.7%) compared to transparent soap control (18.3%) due to the evaporation of water during the melting and mixing. The hardness of transparent soaps with OPAL M3 and OPAL M4 was found to be softer than transparent soaps with OPAL M1 and OPAL M2. By adding OPAL extracts, the foaming ability and stability were not affected. Transparent soap formulated with OPAL M1 extract exhibited the highest percentage of antioxidant activity (3.7%). The use of OPAL extracts is recommended in transparent soap as it provides natural colourant.

EFFECT OF BIOFUEL ON LIGHT-DUTY VEHICLES ENGINE PERFORMANCE AND LUBE OIL DEGRADATION

Biofuel is a renewable, biodegradable and non-toxic fuel that is an alternative to fossil fuel. However, the long-term effect of biodiesel on internal combustion engine operation is not extensively studied. Thus, this study examined the effect of B5 biofuel (blend of 5% refined, bleached and deodourised palm olein oil (RBDPOo) and 95% automotive diesel oil (ADO) on engine performance and lube oil degradation of lightduty vehicles, i.e. Mercedes Benz (M), Mitsubishi Storm (MS) and Toyota Hilux (TH), up to 80 000 km mileage. ADO was also used for each vehicle brand for comparison. The engine power and torque were examined using chassis dynamometer. Analysis on wear metal content of lube oil was conducted to indicate engine deterioration level. Results showed insignificant deterioration on engine performance of M and MS vehicles using ADO and B5 but B5 vehicles showed lower torque reduction than ADO vehicles. For lube oil analysis, the properties and wear metal contents in B5 vehicles were within acceptable limit as suggested by the International Council on Combustion Engines (CIMAC). Results of this study concluded that the B5 biofuel can be potentially used for selected vehicle brands without engine modifications and normal service intervals can be applied for B5 vehicles.

HISTONE MODIFICATION MARKS IMPROVE IDENTIFICATION OF OIL PALM TRANSCRIPTION START SITES

Epigenetic regulation involves modifications of chromatin components such as post-translational modifications of histone proteins, methylation of cytosines in deoxyribonucleic acid (DNA), the involvement of small RNA and chromatin remodeling. Numerous methods have been established to understand the epigenetic control of agronomically important traits. Chromatin immunoprecipitation with sequencing (ChIP-Seq) is widely used to identify the binding sites of transcription factors or modified histones on a genome-wide scale. Here, ChIP-Seq targeting H3K4me3 and H3K27me3 marks in oil palm spears were conducted to examine genomic regions enriched with these histone modifications. Due to low DNA amounts from ChIP experiments, the data analysis workflow was optimised based on ChIP-Seq workflows on other plants. Mapping to specific target regions revealed that the histone mark peak positions were located close to predicted transcription start sites (TSS). This agrees with H3K4me3 and H3K27me3 profiles in other plants where H3K4me3 marks are generally associated with active genes and promoter regions while H3K27me3 marks are linked to repressed genes. Gene-wide mapping for low coverage ChIP-Seq data showed that H3K4me3 and H3K27me3 profiles on the oil palm genome corresponded to consensus histone profiles in other plants. This is the first ChIP-Seq analysis workflow reported for oil palm spears, which can be used to develop future oil palm ChIP-Seq studies.

NUTRIENT ENHANCEMENT OF PALM KERNEL CAKE VIA SOLID STATE FERMENTATION BY LOCALLY ISOLATED Rhizopus oryzae ME01

Palm kernel cake (PKC) is abundantly generated in palm kernel crushing plant throughout the year. Its use as monogastric animal food source is very limited due to its high fibre and moderate protein content. Therefore, this study is aimed to enhance PKC nutritional value, particularly the protein content through solid state fermentation (SSF), using a locally isolated fungus. Fungal identification was performed using partial 18S ribosomal ribonucleic acid (rRNA) nucleotide sequence. A fungus containing 600 base pairs was sequenced and aligned with GenBank database and named Rhizopus oryzae ME01. SSF was carried out using palm kernel expeller (PKE) which is mechanical pressed and palm kernel cake (PKC) which is solvent extracted, as a single carbon source with minimum mineral addition. Results showed that SSF successfully increased crude protein and ash content of fermented PKC and PKE, respectively. Interestingly, this study also found that the size of PKC’s particle had impacted protein content of fermented palm kernel cake (fPKC) during SSF. PKC which has a smaller and uniform size than PKE, gave higher crude protein increment than fermented palm kernel expeller (fPKE). However, the protein content of fPKE had increased by 7.64% more than fPKC which was only 3.45%. Thus, fPKE appeared to enhance PKE’s nutrient value, especially for monogastric animal feed applications.

DOES PALM MID FRACTION AFFECT ADULT SATIETY?

Dietary fats with different melting characteristics, fatty acids chain length and positional distribution may affect postprandial gut hormones and satiety response. We investigated the effects of palm mid fraction (PMF) (POP-rich), shea stearin (SS) (SOS-rich) and high oleic sunflower oil (HOSF) (OOO-rich) with either palmitic, stearic or oleic acid predominance at the sn-1 and sn-3 positions on gut hormone concentrations and satiety. A randomised, double-blind crossover (3 × 3 arms) orthogonal Latin-square study was conducted on 36 healthy adults (18 males, 18 females; average aged 23 years). Each subject received ~50 g of test fat incorporated in a muffin in random order, two weeks apart, over a six-week period. Blood samples were collected for a 3-hr period. We found that PMF- and HOSF-rich diets with either palmitic or oleic acid at the sn-1 and sn-3 positions exerted significantly higher (P<0.05) postprandial glucose dependent insulinotropic polypeptide (GIP) compared to SS-rich diet. However, plasma glucagon like-peptide 1 (GLP-1), peptide YY (PYY), ghrelin and visual analogue scale (VAS) (P>0.05) were not affected. These results suggested that PMF- and HOSF-rich diets increased the secretion of GIP that may promote satiety response in human adults.

SHORT COMMUNICATION: SIMPLIFIED APPROACH FOR EARLY IDENTIFICATION OF SPONTANEOUS OIL PALM HAPLOID (Elaeis guineensis)

Haploid technology facilitates the production of completely homozygous plants that are desirable in crop breeding. Having just one complete set of chromosomes in a haploid individual allows it to be doubled to produce a normal but pure 2n diploid plant. Here, we report a simple way to identify natural haploids of oil palm (Elaeis guineensis Jacq.) from screening 6400 abnormal germinated seeds. Initially, the germinated seeds were selected based on 12 unique ‘off-type’ morphological characteristics. The selected seeds were then grown and the seedlings were subjected to a second selection for three distinctive characteristics. Ploidy analysis with flow cytometry (FCM) and chromosome karyotyping confirmed the haploidy of one seedling with stunted height and size. Further analysis with the True-to-Type single nucleotide polymorphism (SNP) panel demonstrated that the plant was homozygous at all the loci tested, confirming its haploid status. This study has established a simple and systematic strategy that assists in accelerating early identification of oil palm spontaneous haploid.

MORPHO-PHYSIOLOGICAL ASSESSMENT OF OIL PALM (Elaeis guineensis Jacq.) SEEDLINGS EXPOSED TO SIMULATED DROUGHT CONDITIONS

Elaeis guineensis Jacq. (oil palm) production is threatened by drought due to climate change and anthropogenic deforestation. This study aims to understand how drought conditions contribute to changes in foliar nitrate-nitrogen concentration as well as the effects on the growth and development of oil palm seedlings. Seventy oil palm seedlings were maintained in a screen house and subjected to simulated drought conditions. There was a significant reduction in the number of leaves with increased drought exposure from 10 to four per plant. Oil palm leaves exposed to higher drought levels had less broad leaves, with leaf area ranging from 133.25-172.22 cm2 compared to the control (383.73 cm2). The foliar yield per plant was low in plants exposed to extreme drought condition (2.27 g), compared to 71.98 g in the control. Moreover, total drought-exposed oil palm seedlings had the highest concentration of nitrate-nitrogen. E. guineensis exposed to no-drought conditions had more roots (18 roots) than those exposed to total or partial drought (6-10 roots per plant). Overall, there was a decrease in height, leaf area and the number of leaves for most of the seedlings exposed to drought condition, which might be detrimental to their photosynthetic ability and growth.

BIRD SPECIES RICHNESS, ABUNDANCE AND THEIR FEEDING GUILD ACROSS OIL PALMS DEVELOPMENT THROUGH MIST-NETTING METHOD IN BETONG, SARAWAK

There are a lot of studies comparing birds in oil palm plantation with forests and other crop ecosystems but less on bird across drained peat swamp forest converted to oil palm plantation. This study assessed the bird species richness, abundance and their feeding guild change throughout the oil palm development phases including drained peat swamp forest (DPSF), cleared land (CL), one-year-old palm (1YOP), two-year-old palm (2YOP), three-year-old palm (3YOP), four-year-old palm (4YOP) and five-year-old palm (5YOP). Sixty-seven species of bird were recorded across the development phases through mist-netting method, of which 35.8% were only recorded in DPSF, 19.4% of the DPSF bird species continued to be recorded after the forest conversion to oil palm plantation, and 44.8% of bird species were additional species from DPSF species, appearing following the planting of oil palm. Species richness of bird was significantly higher in DPSF than CL but similar level to those in oil palm plantation. Even though level of species richness in oil palm plantation was similar level to those in DPSF, Non-metric Multidimensional Scaling revealed that bird compositions were different according to the three grouping habitats; DPSF, CL and oil palm plantation. Species richness of insectivorous guild was ranked higher along the oil palm development phases. Species abundance of insectivorous was ranked higher at the early stage of development then omnivorous guild recorded abundant once the Yellow-vented Bulbul started to dominate oil palm of more than 2YOP. Good understanding on bird’s distribution change across the conversion of forest to oil palm development gives a better idea on how to minimise land disturbance during plantation operations.

THE EFFECTS OF RECYCLING PALM PRESSEDFIBRE OIL ON CRUDE PALM OIL QUALITY

Palm pressed-fibre oil (PPFO) is known as a phytonutrients rich oil. PPFO was practically recycled back to the crude palm oil (CPO) processing line to increase oil extraction rates. This study evaluated the effect of blending CPO with PPFO at different PPFO dosage from 5%-25% (w/w) on blended oil quality. Free fatty acid (FFA) of blended oils increased from 3.42%-3.91%, while deterioration of bleachability index (DOBI) and iodine value (IV) decreased from 2.76 to 2.33 and 51.96 ± 0.37 to 50.21 ± 0.03, respectively. Minor components amount in blended oils were found to increase with carotenoids (539-654 ppm), squalene (475- 1201 ppm), sterols (433-808 ppm), phospholipids (34.67-63.84 ppm) and vitamin E (1185-1626 ppm). The oxidative stability of blended oils was improved (14.31-16.76 hr) but chlorine, iron and copper content were found to increase from 3.85-7.49 ppm, 13.58-17.63 ppm and 0.19-0.38 ppm, respectively. Although blending PPFO would deteriorate some quality properties of CPO, nonetheless, PPFO is rich with phytonutrients, therefore signifying its potential applications in pharmaceuticals and food industry.

THE EFFECT OF MICROWAVE TREATMENT AND DELAYED HARVESTING ON OIL PALM FRUITLETS (Elaeis guineensis) OIL QUALITY

Conventional palm oil mill practice not only processes unwanted empty bunches in sterilisation stage but also produces large amount of wastewater. The oil extraction rate (OER) of the mill is affected by the quality of the oil palm fresh fruit bunches (FFB), which may consist of unripe fruit with less oil content, and uneven distribution of steam throughout the bunches during sterilisation. Besides the FFB, oil palm mills also process loose fruits either collected from the plantations or detached during FFB transportation to the mills. As these loose fruitlets are void of the stalk and core of the bunch, processing them in the same way as FFB is not cost effective. The objective of this study was to carry out processing of fruitlets using microwave, followed by solvent extraction. Loose fruitlets detached in plantations usually come from the outer layer of bunch which contains more oil compared to the inner layer. The following methodology was adopted in this study: 1) optimisation of load per batch for microwave processing of fruitlets, 2) optimisation of microwave heating parameters, and 3) processing of fruitlets detached from the same bunch over 21 days. Fruitlets were sterilised via microwave (2.4 GHz, 900 W, medium power) and its oil is extracted by n-hexane. Optimum load of 170-220 g fruitlets per batch with 3 min heating left the fruitlets to be well conditioned, i.e., softened mesocarp and unburned kernel. The fruitlets get heated rapidly by microwave due to instantaneous dielectric heating effect of moisturised materials. Quality of oil extracted from fruits detached from the same bunch collected over 21 days was investigated. Free fatty acids (FFA), deterioration of bleachability index (DOBI), and oxidative stability of the oil was found to have reduced from 1.3%, 4.32 and 15.18 hr to 6.5%, 0.86 and 5.28 hr, respectively.

SOIL FUNGAL COMPOSITION AND DIVERSITY IN OIL PALM PLANTATION AT SUNGAI ASAP, SARAWAK, MALAYSIA

A study was carried out to compare the soil fungal composition and diversity in oil palm plantation with the adjacent secondary forest at Sungai Asap, Sarawak, Malaysia using denaturing gradient gel electrophoresis (DGGE). Findings revealed that soil fungal composition in the oil palm plantation was significantly different compared with undisturbed secondary forest (SF1) and disturbed secondary forest (SF2) by forming three main clusters as shown in the principal component analysis (PCA). Furthermore, DGGE profile revealed that the banding pattern of oil palm planted area (OPPA) remained diverse throughout the assessment years. However, DGGE banding patterns of SF1 and SF2 showed similarities as noted in the dry season (June 2011) whereby both clusters were overlapped. The composition of soil fungal community in oil palm plantation was dominated by fungi from the phylum Ascomycota whereas secondary forests were dominated by fungi from Basidiomycota. Biodiversity indices showed that the soil fungal diversity in SF1 was higher than SF2 and OPPA. It was postulated that there was possible interactions between soil fungal communities with plantation activities thereby soil fungal communities were shifted in order to acclimatise with new environments in the plantation.

A PROOF-OF-CONCEPT STUDY: DETERMINING THE GEOGRAPHICAL ORIGIN OF CRUDE PALM OIL WITH THE COMBINED USE OF GC-IMS FINGERPRINTING AND CHEMOMETRICS

Current administrative controls used to verify geographical provenance within palm oil supply chains require enhancement and strengthening by more robust analytical methods. In this study, the application of volatile organic compound fingerprinting, in combination with five different analytical classification models, has been used to verify the regional geographical provenance of crude palm oil samples. For this purpose, 108 crude palm oil samples were collected from two regions within Malaysia, namely Peninsular Malaysia (32) and Sabah (76). Samples were analysed by gas chromatography-ion mobility spectrometer (GC-IMS) and the five predictive models (Sparse Logistic Regression, Random Forests, Gaussian Processes, Support Vector Machines and Artificial Neural Networks) were built and applied. Models were validated using 10-fold cross-validation. The area under curve (AUC) measure was used as a summary indicator of the performance of each classifier. All models performed well (AUC 0.96) with the Sparse Logistic Regression model giving best performance (AUC = 0.98). This demonstrates that the verification of the geographical origin of crude palm oil is feasible by volatile organic compound fingerprinting, using GC-IMS supported by chemometric analysis.

MAPPING THE NITROGEN STATUS ON IMMATURE OIL PALM AREA IN MALAYSIAN OIL PALM PLANTATION WITH AUTOPILOT TRACTOR-MOUNTED ACTIVE LIGHT SENSOR

This study was conducted to identify and visualise spatially the Nitrogen (N) status on immature oil palm area with an autopilot tractor-mounted active light sensor (ALS) in a Malaysian oil palm plantation. All the measurements taken by the ALS were assessed ‘on-the-go’ at every second while the tractor was moving on the field with autopilot steering mode. The N status was analysed based on 46% of the N content in urea and 40 kg ha–1 N application rate for a standard fertiliser requirement for immature oil palm. The ordinary kriging method was used to produce the interpolated maps of the N status by means of the ArcGIS 10.3 software. It was found that mean N-as applied rate per hectare read by the sensor was 1.62% lower than the recommended one. By showing such very small difference in mean rates, generally, the system showed its effectiveness in monitoring N status on immature oil palm. The interpolated maps also successfully displayed spatial variability of the N status on immature oil palm area, which are useable for reference in applying variable rate application (VRA) to economise the use of fertiliser on the said crop.

OPTIMISATION OF ALKALI EXTRACTION OF PALM KERNEL CAKE PROTEIN

Palm kernel cake (PKC) is commonly used in animal feed, particularly as ruminant feed to supply protein and energy. There is little information on the properties of protein concentrate produced from the PKC which constitute 14%-17% of the meal. Protein concentrates can be produced from PKC using alkali extraction, where PKC is extracted with an alkali solution and followed by precipitation at the isoelectric point. Thus, this study examined the effects of extraction using several extractants at different conditions; meal ratio of 0.5:50-3.0:50 g ml–1, concentration of 0.1-1.0 M, pH 1-12, temperature of 30°C-80°C and time duration of 30-180 min. Sodium hydroxide (NaOH) was found to be the most suitable alkali for protein extraction. Optimum conditions for protein extraction were obtained at 1.0 M NaOH concentration, 50°C temperature, meal to solvent ratio of 2:50 (g ml–1), pH 12 and 120 min. The extracted protein was isolated by isoelectric precipitation at pH 3.5 using 1.0 M hydrochloric acid (HCI). The percentage of protein recovery was 80%-86%. Protein content in the recovery ranged from 45%-50%. Analysis by high performance liquid chromatography (HPLC) showed that arginine, glutamic acid, phenylalanine and leucine were the most abundant amino acids in the concentrates.

THE EFFECT OF SATURATED AND UNSATURATED FATTY ACID COMPOSITION IN BIO-BASED LUBRICANT TO THE TRIBOLOGICAL PERFORMANCES USING FOUR-BALL TRIBOTESTER

The performances of bio-based lubricants were influenced by the strength of its molecular interaction between the fatty acid chain and iron molecules on metal surfaces. In this study, the fatty acid compositions of refined, bleached and deodorised palm oil (RBDPO), double fractionated palm olein (SPL) and palm mid olein (PMO) were determined by using gas-liquid chromatography (GLC). Four-ball tribotester was used to evaluate the performance of the lubricants in terms of friction coefficient, wear scar diameter (WSD) and surface roughness (Ra). It was found that PMO with high saturated fatty acid content exhibited excellent tribological characteristics subjected to various temperatures and rotational speeds. However, there was no significant impact observed at extreme pressure (EP) conditions. The physical wear condition was also discussed and analysed.

EVALUATION OF MITOCHONDRIAL DNA ISOLATION METHODS FOR OIL PALM (Elaeis guineensis) LEAF

An efficient preparation of pure and intact mitochondrial deoxyribonucleic acid (mtDNA) that is free from nuclear DNA contamination is a prerequisite to study the molecular complexities of the organellar genome and gene structure in oil palm. Different extraction methods have been reported for mtDNA isolation from different plants. Using oil palm leaf tissues that are present in abundance, three methods were tested and modified to isolate mtDNA. The methods used vary primarily at the purification steps, either by using phenol/chloroform or density gradient centrifugation. High ionic alkaline buffer coupled with differential centrifugation were employed in Method I. While Methods II and III utilised the discontinuous sucrose and Percoll gradient centrifugation for mitochondria isolation, respectively. Method III provided good quality mtDNA from green leaves, yielding ~6.3 μg g–1 tissue. Restriction digest and polymerase chain reaction (PCR) for regions specific to mitochondrial, nuclear and chloroplast DNA further verified the quality of the mtDNA from Method III, which had the least plastid DNA contamination. Method III that incorporated Percoll density gradient centrifugation was the most efficient and provided good quality mtDNA without nuclear DNA contamination for sequencing applications and studies requiring pure mtDNA.

A COMPARATIVE STUDY OF BACTERIAL COMMUNITIES DETERMINED BY CULTURE-DEPENDENT AND-INDEPENDENT APPROACHES IN OIL PALM PLANTED ON TROPICAL PEATLAND

A combination of deoxyribonucleic acid (DNA)-based method and sequencing technologies have initiated a new era of soil microbial ecology to examine the patterns of bacterial communities in tropical peatland. The aims of the study are to verify and compare the bacterial communities in a 12-year-old oil palm plantation on peat of Sibu, Sarawak, Malaysia using culture-dependent and culture-independent approaches. The bacterial diversity identified from both approaches were amplified using 16S ribosomal deoxyribonucleic acid (rDNA) (341/907) primer, sequenced and analysed. This resulted in recovering a total of 227 bacterial isolates belonging to four major phyla accumulated from 22 genera. Meanwhile, about 216 denaturing gradient gel electrophoresis (DGGE) bands were excised, which corresponded to 195 different bacterial species from 20 different phyla by culture-independent method. Although both approaches detected a total of four predominant bacterial phyla (Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes), in general, different taxonomic sequences were targeted by each method. In comparison to culture-dependent, polymerase chain reaction-(PCR) DGGE method identified a higher rate of bacterial diversity and richness and also detected non-culturable bacteria. Thus, this suggests that culture-independent method was showed to be more efficient on the bacterial diversity identification that will lead towards unravelling the hidden bacterial species associated with agricultural practices carried out in Southeast Asia peatland.