Biogas Production and Determination of Methanogens from Digester - Treated Palm Oil Mill Effluent

Due to increasing awareness of the risk of the environmental pollution and emission of green house gases (GHG) that caused global warming, a study of palm oil mill effluent (POME) treatment using biological processes in close digesters has been conducted. Potentially beneficial methane gas production from this treatment has driven the objectives of this study to explore the methanogens from POME sludge and their characteristic in order to improve the POME treatment efficiency. A pilot plant digester with 500 m3 volume was operated for one year and biogas and methane production profiles were monitored daily. Parameters used for monitoring were pH, temperature, volatile fatty acids, chemical oxygen demand, biogas and methane concentration during the treatment. Structure of the flocs formation and methanogenic bacteria isolated from this digester was also carried out in order to understand the microbiological characteristics of the bioprocess involved Specific methanogenic activity test (SMA) and microscopic observation were carried out to support the existence of the methanogens that were able to produce methane gas. During POME treatment process, the highest methane concentration obtained was 55 % (v/v) and chemical oxygen demand (COD) removal efficiency was up to 95%. Anticipated active biomasses retained in the digester were determined as total solids (TS) and volatile suspended solids (VSS) at 2.5% and 1.5%, respectively. SMA test for acetolastic methanogens was determined in the range of 0.05 - 1.3 g COD/ g VSS/d. Microscopic observation of the sludge and isolated colonies have shown that the digester systems were dominated by microorganism resemble to Methanosaeta sp. and fluorescence microscope has proved that this microorganism exhibited autofluorescence green color

Feasibility of palm oil mill effluent sludge oil as cheaper carbon sources in biosurfactant production

Biosurfactant have received growing interest in recent years due to its capability in biodegradation of oils that would increase oil solubility in water, reduction of surface tension and low level of toxicity imposed to environment. Therefore, biosurfactant is less competitive than synthetic products, due to high production costs. Hence, low grade and cheaper carbon sources such as palm oil mill effluent (POME) sludge oil is used as alternative substrate in biosurfactant production of Pseudomonas aeruginosa RW9. In this work, different types and concentrations of carbon and nitrogen sources were supplemented in the mineral salt medium to obtain an optimal biosurfactant production. Rhamnolipids surfactant produced was extracted and purified by using solvent extraction process and silica gel column chromatography, respectively. The purified samples produced were characterized by emulsification index (E24,%), surface tension, NMR, HPLC and GC-MS

Hydrothermal pretreatment enhanced enzymatic hydrolysis and glucose production from oil palm biomass

The present works investigate hydrothermal pretreatment of oil palm empty fruit bunch and oil palm frond fiber in a batch tube reactor system with temperature and time range from 170 to 250 °C and 10 to 20 min, respectively. The behavior of soluble sugars, acids, furans, and phenols dramatically changed over treatment severities as determined by HPLC. The cellulose-rich treated solids were analyzed by SEM, WAXD, and BET surface area. Enzymatic hydrolysis was performed from both pretreated slurries and washed solid, and data obtained suggested that tannic acid derived from lignin degradation was a potential cellulase inhibitor. Both partial removal of hemicellulose and migration of lignin during hydrothermal pretreatment caused structural changes on the cellulose–hemicellulose–lignin matrix, resulting in the opening and expansion of specific surface area and pore volume. The current results provided important factors that maximize conversion of cellulose to glucose from oil palm biomass by hydrothermal process

Multiple stage pretreatment affecting the properties of nanocellulose from oil palm frond

Cellulose extraction is an important step prior to nanocellulose production from lignocellulosic materials. The important view of present study rely on pretreatment method for cellulose extraction by comparing their effect on properties of nanocellulose. Oil palm frond was choose in focusing study as the potential value added product. Two pretreatment method were conduct which are multiple stage pretreatment and compared with single stage pretreatment. Peracetic acid was used as totally chlorine free (TCF) bleaching as it is environmental favorable. Multiple stage is the combination of physical, enzymatic and alkaline treatment while single stage represent for soda pulping process using 14% active alkaline charge in high temperature and pressure (160°C, 0.6-1.0 MPa). For multiple stage, superheated steam (300°C, 9 min) used as a prospective in open the fiber structure to allow the subsequent of enzymatic hydrolysis using xylanase. The xylanase was then access to catalyze 1, 4-beta-xylosidase which results in removal of hemicellulose and increase the cellulose content. In addition, xylanase enhanced the delignification process using alkaline treatment of 10% sodium hydroxide. Cellulose nanofibrillation was then conducted using a wet disc mill (WDM). Chemical analysis revealed the cellulose purity from multiple stage and single stage pretreatment with 83.4% and 94.6%. By characterization, the cellulose from multiple stage pretreatment results in high degree of polymerization up to 1,226, higher crystallinity (69.5%) and reach maximum thermal degradation at 326°C. The characteristics of cellulose eventually affected the nanocelluloses properties and by morphology, the nanocellulose produced from both treatment have the diameter size less than 100 nm

Hydrothermal pretreatment of mixed oil palm biomass

Oil palm biomass has high amount of carbohydrates which potentially to be converted into biosugar. Due to complex structure of the lignocellulosic component, pretreatment is needed to allow the penetration of cellulase into cellulose. While several pretreatments were available to open up the lignocellulosic structure, hydrothermal pretreatment process was chosen as the effectiveness and environmental-friendly process. Earlier research using individual biomass in different pretreatment processes had proven great effect on conversion of glucose. In this study, a pretreatment process was tested on mixed biomass to adapt bulk amount of biomass produced daily. The aim is to achieve high cellulose content after hydrothermal preatment. Mixing ratio of oil palm biomass was 1:1:1 of 2.0 mm size that involved empty fruit bunch, mesocarp fibre and frond fiber, and then continued to hydrothermal pretreatment with different severity factors (log, Rₒ) of 2.48 until 5.14. Chemical composition of untreated and pretreated mixed oil palm biomass was determined using acid hydrolysis. Each sample was examined with scanning electron microscope, wide-angle x-ray diffraction, and Brunauer-Emmett-Teller surface area analyses to check on the structure of biomass after pretreatment. High cellulose content which 50.1±0.3% was successfully achieved at temperature of 190˚C in 10 min. In conclusion, this experiment succeeded to approve that by hydrothermal pretreatment can give high cellulose content in mixed oil palm biomass under low temperature and short time

Pseudogene product YqiG is important for pflB expression and biohydrogen production in Escherichia coli BW25113

Pseudogenes in the Escherichia coli genome are assumed to be non-functional. In this study, Keio collection BW25113∆yqiG and YqiG-producing strain (BW25113/pCA24N-YqiG) were used to evaluate the importance of pseudogene yqiG in hydrogen metabolism. Our results show pseudogene protein YqiG was identified as an essential protein in the production of biohydrogen from glucose. The mutant yqiG decreased biohydrogen production from 37 µmol mg−1 protein to 6 µmol mg−1 protein compared to the wild-type strain, and glucose consumption was reduced by 80%. Through transcriptional analysis, we found that the yqiG mutation represses pflB transcription tenfold; pflB encodes pyruvate-formate lyase, one of the key enzymes in the anaerobic metabolism of E. coli. Moreover, production of YqiG stimulated glycolysis and increased biohydrogen productivity 1.5-fold compared to that of the wild-type strain. Thus, YqiG is important for the central glycolysis reaction and is able to influence hydrogen metabolism activity in E. coli

Metabolic engineered Escherichia coli to enhance polyhydroxyalkanoates production

Polyhydroxyalkanoates (PHAs) are linear polyesters produced through fermentation of sugar or lipid. Biosynthesis of PHA consists of three enzymes which are acetyl-CoA acetyltransferase (phaA), acetoacetyl-CoA reductase (phaB) and PHA synthase (phaC). Comamonas sp. is one of the strains commonly used for PHA production. Under growth conditions PHA is synthesized by excess of carbon sources and other essential nutrients. In order to develop higher PHA production from bacterial respond strategy, PHA biosynthesis operon of Comamonas sp. EB172 was introduced into Escherichia coli BW25113 through pGEMT vector. E. coli was chosen due to the complete genome information and the absence of depolymerisation gene, phaZ. The presence of PHA operon in E. coli has yielded PHA about 46% (w/w) with glucose as the carbon source. Therefore, the aim of this study is to improve the PHA production by screening of specific genes related to metabolic pathway of PHA in E. coli. Single gene deletion strains of keio collection harboring PHA biosynthesis operon of Comamonas sp. EB172 were used. Six genes pgi, frdC, fdnG, gltA, pta, and poxB were found to be associated with PHA metabolism activity. Second genes knockouts were introduced in through P1 transduction in order to improve PHA production and E. coli BW25113 frdC gltA::kan was shown an improvement of PHA production 53% compared to the wild type

Ecotoxicological assessment of palm oil mill effluent final discharge by zebrafish (Danio rerio) embryonic assay

Most palm oil mills adopted conventional ponding system, including anaerobic, aerobic, facultative and algae ponds, for the treatment of palm oil mill effluent (POME). Only a few mills installed a bio-polishing plant to treat POME further before its final discharge. The present study aims to determine the quality and toxicity levels of POME final discharge from three different mills by using conventional chemical analyses and fish (Danio rerio) embryo toxicity (FET) test. The effluent derived from mill A which installed with a bio-polishing plant had lower values of BOD, COD and TSS at 45 mg/L, 104 mg/L, and 27 mg/L, respectively. Only mill A nearly met the industrial effluent discharge standard for BOD. In FET test, effluent from mill A recorded low lethality and most of the embryos were malformed after hatching (half-maximal effective concentration (EC50) = 20%). The highest toxicity was observed from the effluent of mill B and all embryos were coagulated after 24 h in samples greater than 75% of effluent (38% of half-maximal lethal concentration (LC50) at 96 h). The embryos in the effluent from mill C recorded high mortality after hatching, and the survivors were malformed after 96 h exposure (LC50 = 26%). Elemental analysis of POME final discharge samples showed Cu, Zn, and Fe concentrations were in the range of 0.10–0.32 mg/L, 0.01–0.99 mg/L, and 0.94–4.54 mg/L, respectively and all values were below the effluent permissible discharge limits. However, the present study found these metals inhibited D. rerio embryonic development at 0.12 mg/L of Cu, and 4.9 mg/L of Fe for 96 h-EC50. The present study found that bio-polishing plant installed in mill A effectively removing pollutants especially BOD and the FET test was a useful method to monitor quality and toxicity of the POME final discharge samples

Improved biogas production from palm oil mill effluent by a scaled-down anaerobic treatment process

This is a scale-down study of a 500-m3 methane recovery test plant for anaerobic treatment of palm oil mill effluent (POME) where biomass washout has become one of the problems because of the continuous mixing of effluent during anaerobic treatment of POME. Therefore, in this study, anaerobic POME treatment using a scaled down 50-l bioreactor which mimicked the 500-m3 bioreactor was carried out to improve biogas production with and without biomass sedimentation. Three sets of experiments were conducted under different conditions in terms of biomass sedimentation applied to the system. The first experiment was operated under semi-continuous mode whereas the second and third experiments were operated based on mix and settle mode. As expected, biomass retention improved the anaerobic process as the POME treatment incorporated with mix and settle system were able to operate at an organic loading rate (OLR) of 3.5 and 6.0 kg COD/m3/day respectively, while the semi continuous operated anaerobic treatment only achieved OLR of 3.0 kg COD/m3/day. The highest biogas and methane production rates achieved were 2.42 m3/m3 of reactor/day and 0.992 m3/m3 of reactor/day, respectively at OLR 6.0 kg COD/m3/day. The biomass or solids retention in the reactors was represented by the total solids measured in this study

Combination of superheated steam with laccase pretreatment together with size reduction to enhance enzymatic hydrolysis of oil palm biomass

Oil palm empty fruit bunch (OPEFB) and oil palm mesocarp fiber (OPMF) are lignocellulosic biomass that abundantly generated in palm oil mills. However, the presence of these oil palm wastes has created a major disposal problem. Current treatment is either by mulching at the plantation of dumping at side of the mill. Since these materials are rich in carbohydrate these OPEFB and OPMF has been widely reported as suitable raw materials to produce fermentable sugars. However, the presence of lignin and hemicellulose in their composition hinders the access of cellulase to hydrolyse cellulose. Effective pretreatments are required to reduce the recalcitrance of lignocellulosic structures and therefore improve the fermentable sugars production. Combination of physico-chemical and biological pretreatment was proposed to obtain better fermentable sugar production from OPEFB and OPMF. Physico-chemical pretreatment like superheated steam (SHS) was used in this study as it can modify the lignocellulosic materials. However, based on previous studies, SHS pretreatment alone does not able to produce high fermentable sugars. Therefore combination pretreatment of SHS with laccase from Trametes Versicolor has been studied to improve delignification and at the same time enhance the production of fermentable sugars. In addition, the effect of size reduction prior to laccase pretreatment was also conducted to reduce particle size to expose large surface area so that the laccase can accessible attack to the lignin structure. This study revealed that glucose yield was successfully enhanced by combining SHS with laccase pretreatment together with size reduction of OPEFB and OPMF