Isolation and characterization of high hydrogen-producing strain Clostridium beijerinckii PS-3 from fermented oil palm sap

Felled oil palm trunk (OPT) (25 years old) is an abundant biomass in Southern Thailand. The OPT composition was 31.28–42.85% cellulose, 19.73–25.56% hemicellulose, 10.74–18.47% lignin, 1.63–2.25% protein, 1.60–1.83% fat, 1.12–1.35% ash and trace amount of minerals (0.01–0.40%). Oil palm sap extracted from OPT was found to contain 15.72 g/L glucose, 2.25 g/L xylose, and 0.086 g/L arabinose. A total of twenty samples from hot springs (45–75 °C and pH 6.5–8.4), oil palm sap and palm oil mill effluent were enriched for isolation of hydrogen-producing bacteria. The highest hydrogen-producing strain was isolated from oil palm sap and identified as Clostridium beijerinckii PS-3 using biochemical test and 16S rRNA gene analysis. Among various carbon sources tested, glucose, xylose, starch and cellulose were the preferred substrates for hydrogen production. The strain PS-3 could produce the maximum hydrogen yield of 140.9 ml H₂/g total sugar and the cumulative hydrogen production of 1973  ml/L-oil palm sap. Therefore, C. beijerinckii PS-3 is a potential candidate for fermentative hydrogen production from mixed sugars of the oil palm sap.     

Effect of initial pH,nutrients and temperature on hydrogen production from palm oil mill effluent using thermotolerant consortia and corresponding microbial communities

Thermotolerant consortia were obtained by heat-shock treatment on seed sludge from palm oil mill. Effect of the initial pH (4.5–6.5) on fermentative hydrogen production palm oil mill effluent (POME) showed the optimum pH at 6.0, with the maximum hydrogen production potential of 702.52 mL/L-POME, production rate of 74.54 mL/L/h. Nutrients optimization was investigated by response surface methodology with central composite design (CCD). The optimum nutrients contained 0.25 g urea/L, 0.02 g Na₂HPO₄/L and 0.36 g FeSO₄·7H₂O/L, giving the predicted value of hydrogen production of 1075 mL/L-POME. Validation experiment revealed the actual hydrogen production of 968 mL/L-POME. Studies on the effect of temperature (25–55 °C) revealed that the maximum hydrogen production potential (985.3 mL/L-POME), hydrogen production rate (75.99 mL/L/h) and hydrogen yield (27.09 mL/g COD) were achieved at 55, 45 and 37 °C, respectively. Corresponding microbial community determined by the DGGE profile demonstrated that Clostridium spp. was the dominant species. Clostridium paraputrificum was the only dominant bacterium presented in all temperatures tested, indicating that the strain was thermotolerant.     

Photofermentive production of biohydrogen from oil palm waste hydrolysate

Oil palm empty fruit bunch (OPEFB) was hydrolyzed with dilute sulfuric acid (6% v/v; 8 mL acid per g dry OPEFB) at 120 °C for 15-min to release the fermentable sugars. The hydrolysate contained xylose (23.51 g/L), acetic acid (2.44 g/L) and glucose (1.80 g/L) as the major carbon components. This hydrolysate was used as the sole carbon source for photofermentive production of hydrogen using a newly identified photosynthetic bacterium Rhodobacter sphaeroides S10. A Plackett–Burman experimental design was used to examine the influence of the following on hydrogen production: yeast extract concentration, molybdenum concentration, magnesium concentration, EDTA concentration and iron concentration. These factors influenced hydrogen production in the following decreasing order: yeast extract concentration > molybdenum concentration > magnesium concentration > EDTA concentration > iron concentration. Under the conditions used (35 °C, 14.6 W/m² illumination, initial pH of 7.0), the optimal composition of the culture medium was (per L): mixed carbon in OPEFB hydrolysate 3.87 g, K₂HPO₄ 0.9 g, KH₂PO₄ 0.6 g, CaCl₂⋅2H₂O 75 mg, l-glutamic acid 795.6 mg, FeSO₄⋅7H₂O 11 mg, Na₂MoO₂⋅2H₂O 1.45 mg, MgSO₄⋅7H₂O 2.46 g, EDTA 0.02 g, yeast extract 0.3 g). With this medium, the lag period of hydrogen production was 7.65 h, the volumetric production rate was 22.4 mL H₂/L medium per hour and the specific hydrogen production rate was 7.0 mL H₂/g (xylose + glucose + acetic acid) per hour during a 90 h batch culture of the bacterium. Under optimal conditions the conversion efficiency of the mixed carbon substrate to hydrogen was nearly 29%.     

Optimization and microbial community analysis for production of biohydrogen from palm oil mill effluent by thermophilic fermentative process

The optimum values of hydraulic retention time (HRT) and organic loading rate (OLR) of an anaerobic sequencing batch reactor (ASBR) for biohydrogen production from palm oil mill effluent (POME) under thermophilic conditions (60 °C) were investigated in order to achieve the maximum process stability. Microbial community structure dynamics in the ASBR was studied by denaturing gradient gel electrophoresis (DGGE) aiming at improved insight into the hydrogen fermentation microorganisms. The optimum values of 2-d HRT with an OLR of 60 gCOD l⁻¹ d⁻¹ gave a maximum hydrogen yield of 0.27 l H₂ g COD⁻¹ with a volumetric hydrogen production rate of 9.1 l H₂ l⁻¹ d⁻¹ (16.9 mmol l⁻¹ h⁻¹). The hydrogen content, total carbohydrate consumption, COD (chemical oxygen demand) removal and suspended solids removal were 55 ± 3.5%, 92 ± 3%, 57 ± 2.5% and 78 ± 2%, respectively. Acetic acid and butyric acid were the major soluble end-products. The microbial community structure was strongly dependent on the HRT and OLR. DGGE profiling illustrated that Thermoanaerobacterium spp., such as Thermoanaerobacterium thermosaccharolyticum and Thermoanaerobacterium bryantii, were dominant and probably played an important role in hydrogen production under the optimum conditions. The shift in the microbial community from a dominance of T. thermosaccharolyticum to a community where also Caloramator proteoclasticus constituted a major component occurred at suboptimal HRT (1 d) and OLR (80 gCOD l⁻¹ d⁻¹) conditions. The results showed that the hydrogen production performance was closely correlated with the bacterial community structure. This is the first report of a successful ASBR operation achieving a high hydrogen production rate from real wastewater (POME).     

Microbial community analysis of thermophilic mixed culture sludge for biohydrogen production from palm oil mill effluent

The microbial community structure of thermophilic mixed culture sludge used for biohydrogen production from palm oil mill effluent was analyzed by fluorescence in situ hybridization (FISH) and 16S rRNA gene clone library techniques. The hydrogen-producing bacteria were isolated and their ability to produce hydrogen was confirmed. The microbial community was dominated by Thermoanaerobacterium species (∼66%). The remaining microorganisms belonged to Clostridium and Desulfotomaculum spp. (∼28% and ∼6%, respectively). Three hydrogen-producing strains, namely HPB-1, HPB-2, and HPB-3, were isolated. 16S rRNA gene sequence analysis of HPB-1 and HPB-2 revealed a high similarity to Thermoanaerobacterium thermosaccharolyticum (98.6% and 99.0%, respectively). The Thermoanaerobacterium HPB-2 strain was a promising candidate for thermophilic fermentative hydrogen production with a hydrogen yield of 2.53 mol H₂ mol⁻¹hexose from organic waste and wastewater containing a mixture of hexose and pentose sugars. Thermoanaerobacterium species play a major role in thermophilic hydrogen production as confirmed both by molecular and cultivation-based analyses.     

Continuous production of biohydrogen from oil palm empty fruit bunch hydrolysate in tubular photobioreactors

Production of hydrogen by the photosynthetic bacterium Rhodobacter sphaeroides was compared in continuously operated tubular photobioreactors illuminated by natural outdoor sunlight (0.15–66 klux; diurnal cycle) and constant indoor artificial light (10 klux; tungsten lamps). In both cases the operating temperature was 35 °C and the organic carbon source was an acid hydrolysate of oil palm empty fruit bunch (EFB), an agroindustrial waste. In the outdoor photobioreactor, under the best production conditions, the daytime feeding rate of the mixed carbon substrate was 48 mL h^?1 and the average pseudo-steady state hydrogen production rate was 36 mL H₂ L^?1 medium h^?1. The cumulative hydrogen production was 430 mL H₂ L^?1 medium. For the indoor photobioreactor fed at the same rate as the outdoor system, the steady state average hydrogen production rate was 43 mL H₂ L^?1 h^?1 and the cumulative hydrogen production was 517 mL H₂ L^?1 medium. Reducing the feed rate to less than 48 mL h^?1, enhanced the biomass concentration, but reduced hydrogen production in both bioreactors. The sunlight-based cumulative hydrogen production was only about 17% less compared to the artificially lit system, but required only 22% of the electrical energy.     

Enhancement of batch biohydrogen production from prehydrolysate of acid treated oil palm empty fruit bunch

Carbohydrates from hydrolyzed biomass has been a potential feedstock for fermentative hydrogen production. In this study, oil palm empty fruit bunch (OPEFB) was treated by sulfuric acid in different concentrations at 120 °C for 15 min in the autoclave. The optimal condition for pretreatment was obtained when OPEFB was hydrolyzing at 6% (w/v) sulfuric acid concentration, which gave the highest total sugar of 26.89 g/L and 78.51% of sugar production yield. However, the best conversion efficiency of OPEFB pretreatment was 39.47 at sulfuric acid concentration of 4%. A series of batch fermentation were performed to determine the effect of pH in fermentation media and the potential of this prehydrolysate was used as a substrate for fermentative hydrogen production under optimum pretreatment conditions. The prehydrolysate of OPEFB was efficiently converted to hydrogen via fermentation by acclimatized mixed consortia. The maximum hydrogen production was 690 mL H₂ L⁻¹ medium, which corresponded to the yield of 1.98 molH₂/mol_xylose achieved at pH 5.5 with initial total sugar concentration of 5 g/L. Therefore, the results implied that OPEFB prehydrolysate is prospective substrate for efficient fermentative hydrogen conducted at low controlled pH. No methane gas was detected throughout the fermentation.     

Preparation of active hydrogen-producing cultures from palm oil mill sludge for biohydrogen production system

Methods are investigated to prepare active hydrogen (H₂)-producing cultures originating from palm oil mill sludge using dark fermentation. The first successful method that produces potent H₂-producing cultures and avoids growing H₂-consuming methanogens involves heat pretreatment of the sludge at 100 °C for 2 h and then the sludge sample is shocked in an ice bath for 15 min. Subsequently, a glucose solution rich in nutrients (glucose-based substrate) of 14.80 g chemical oxygen demand (COD)/L is fed in to enrich the H₂-producing cultures. The H₂ production reaches 78.63% on day 31. The second method involves acid pretreatment of sludge with 10 M hydrochloric acid at pH 3 for 48 h. Glucose-based substrate of 25.47 g COD/L is fed into the system. The H₂ production is 69.41% on day 27. For both methods, the H₂ production is stable after the H₂ content reached its maximum. The operation is performed semi-continuously using a hydraulic retention time of 1 day and at 30 °C. The optimum bacterial cells-to-COD level of substrate is approximately 0.60 in the start-up medium. The fermentation medium has an optimum initial pH of 5 and a final pH of 5.2–5.3. These two methods are recommended to produce active H₂-producing cultures for plant start-up in bio-H₂ production.     

Potential of hydrogen from oil palm biomass as a source of renewable energy worldwide

Various catastrophes related to extreme weather events such as floods, hurricanes, droughts and heat waves occurring on the Earth in the recent times are definitely a clear warning sign from nature questioning our ability to protect the environment and ultimately the Earth itself. Progressive release of greenhouse gases (GHG) such as CO₂ and CH₄ from development of various energy-intensive industries has ultimately caused human civilization to pay its debt. Realizing the urgency of reducing emissions and yet simultaneously catering to needs of industries, researches and scientists conclude that renewable energy is the perfect candidate to fulfill both parties requirement. Renewable energy provides an effective option for the provision of energy services from the technical point of view. In this context, biomass appears as one important renewable source of energy. Biomass has been a major source of energy in the world until before industrialization when fossil fuels become dominant and researches have proven from time to time its viability for large-scale production. Although there has been some successful industrial-scale production of renewable energy from biomass, generally this industry still faces a lot of challenges including the availability of economically viable technology, sophisticated and sustainable natural resources management, and proper market strategies under competitive energy markets. Amidst these challenges, the development and implementation of suitable policies by the local policy-makers is still the single and most important factor that can determine a successful utilization of renewable energy in a particular country. Ultimately, the race to the end line must begin with the proof of biomass ability to sustain in a long run as a sustainable and reliable source of renewable energy. Thus, the aim of this paper is to present the potential availability of oil palm biomass that can be converted to hydrogen (leading candidate positioned as the energy of the millennium) through gasification reaction in supercritical water, as a source of renewable energy to policy-makers. Oil palm topped the ranking as number 1 fruit crops in terms of production for the year 2007 with 36.90 million tonnes produced or 35.90% of the total edible oil in the world. Its potentiality is further enhanced by the fact that oil constitutes only about 10% of the palm production, while the rest 90% is biomass. With a world oil palm biomass production annually of about 184.6 million tons, the maximum theoretical yield of hydrogen potentially produced by oil palm biomass via this method is 2.16×10¹⁰ kg H₂ year⁻¹ with an energy content of 2.59 EJ year⁻¹, meeting almost 50% of the current worldwide hydrogen demand.     

Mesophilic fermentative hydrogen production from sago starch-processing wastewater using enriched mixed cultures

Biohydrogen (bioH₂) production from starch-containing wastewater is an energy intensive process as it involves thermophilic temperatures for hydrolysis prior to dark fermentation. Here we report a low energy consumption bioH₂ production process with sago starch powder and wastewater at 30 °C using enriched anaerobic mixed cultures. The effect of various inoculum pretreatment methods like heat (80 °C, 2 h), acid (pH 4, 2.5 N HCl, 24 h) and chemical (0.2 g L⁻¹ bromoethanesulphonic acid, 24 h) on bioH₂ production from starch powder (1% w/v) showed highest yield (323.4 mL g⁻¹ starch) in heat-treatment and peak production rate (144.5 mL L⁻¹ h⁻¹) in acid-treatment. Acetate (1.07 g L⁻¹) and butyrate (1.21 g L⁻¹) were major soluble metabolites of heat-treatment. Heat-treated inoculum was used to develop mixed cultures on sago starch (1% w/v) in minimal medium with 0.1% peptone-yeast extract (PY) at initial pH 7 and 30 °C. The effect of sago starch concentration, pH, inoculum size and nutrients (PY and Fe ions) on batch bioH₂ production showed 0.5% substrate, pH 7, 10% inoculum size and 0.1% PY as the best H₂ yielding conditions. Peak H₂ yield and production rate were 412.6 mL g⁻¹ starch and 78.6 mL L⁻¹ h⁻¹, respectively at the optimal conditions. Batch experiment results using sago-processing wastewater under similar conditions showed bioH₂ yield of 126.5 mL g⁻¹ COD and 456 mL g⁻¹ starch. The net energy was calculated to be +2.97 kJ g⁻¹ COD and +0.57 kJ g⁻¹ COD for sago starch powder and wastewater, respectively. Finally, the estimated net energy value of +2.85 × 10¹³ kJ from worldwide sago-processing wastewater production indicates that this wastewater can serve as a promising feedstock for bioH₂ production with low energy input.     

Ultrasonic pretreatment of palm oil mill effluent: Impact on biohydrogen production,bioelectricity generation,and underlying microbial communities

Substrate bioavailabity is one of the critical factors that determine the relative biohydrogen (bioH₂) yield in fermentative hydrogen production and bioelectricity output in a microbial fuel cell (MFC). In the present undertaking, batch bioH₂ production and MFC-based biolectricity generation from ultrasonically pretreated palm oil mill effluent (POME) were investigated using heat-pretreated anaerobic sludge as seed inoculum. Maximum bioH₂ production (0.7 mmol H₂/g COD) and COD removal (65%) was achieved at pH 7, for POME which was ultrasonically pretreated at a dose of 195 J/mL. Maximum value for bioH₂ productivity and COD removal at this sonication dose was higher by 38% and 20%, respectively, than unsonicated treatments. In batch MFC experiments, the same ultrasound dose led to reduced lag-time in bioelectricity generation with concomitant 25% increase in bioelectricity output (18.3 W/m³) and an increase of COD removal from 30% to 54%, as compared to controls. Quantitative polymerase chain reaction (qPCR) tests on sludge samples from batch bioH₂ production reflected an abundance of gene fragments coding for both clostridial and thermoanaerobacterial [FeFe]-hydrogenase. Fluorescence in situ hybridization (FISH) tests on sludge from MFC experiments showed Clostridium spp. and Thermoanaerobacterium spp. as the dominant microflora. Results suggest the potential of ultrasonicated POME as sustainable feedstock for dark fermentation-based bioH₂ production and MFC-based bioelectricity generation.     

High efficient biohydrogen production from palm oil mill effluent by two-stage dark fermentation and microbial electrolysis under thermophilic condition

Biohydrogen production from palm oil mill effluent by two-stage dark fermentation and microbial electrolysis was investigated under thermophilic condition. The optimum chemical oxygen demand (COD) concentration and pH for dark fermentation were 66 g·L⁻¹ and 6.5 with a hydrogen yield of 73 mL-H₂·gCOD⁻¹. The dark fermentation effluent consisted of mainly acetate and butyrate. The optimum voltage for microbial electrolysis was 0.7 V with a hydrogen yield of 163 mL-H₂·gCOD⁻¹. The hydrogen yield of continuous two-stage dark fermentation and microbial electrolysis was 236 mL-H₂·gCOD⁻¹ with a hydrogen production rate of 7.81 L·L⁻¹·d⁻¹. The hydrogen yield was 3 times increased when compared with dark fermentation alone. Thermoanaerobacterium sp. was dominated in the dark fermentation stage while Geobacter sp. and Desulfovibrio sp. dominated in the microbial electrolysis cell stage. Two-stage dark fermentation and microbial electrolysis under thermophilic condition is a highly promising option to maximize the conversion of palm oil mill effluent into biohydrogen.     

Statistical optimization of factors affecting biohydrogen production from xylose fermentation using inhibited mixed anaerobic cultures

The role of different chemical and physical factors in enhancing biohydrogen production from xylose using a mixed anaerobic culture was examined under mesophilic conditions. A fractional factorial design (FFD) 3^(k–p) was used to optimize pH, the oleic acid (OA) concentration and the biomass concentration. The FFD analysis indicated that the hydrogen (H₂) yield was affected by 3 single factors as well as by 2 factor interactions. Under optimum conditions (1600 mg L⁻¹ of oleic acid (OA) and 1900 mg L⁻¹ VSS and pH 6.7), the H₂ yield reached 2.64 ± 0.12 mol mol⁻¹ of xylose (80% of the theoretical yield). Based on the ANOVA and Pareto chart analysis, the linear and quadratic OA and pH terms were significant and the linear and quadratic VSS terms were insignificant. Normally distribution of the residuals was confirmed from the Anderson-Darling (AD) plot. The studentized residuals versus the predicted values plot clearly demonstrated that the data points were randomly scattered.     

Enhancement of biohydrogen production from palm oil mill effluent (POME): A review

Palm oil mill effluent (POME), a wastewater from the most significant agricultural industry in Southeast Asia is produced in tremendous amounts that requires proper management to mitigate its negative environmental effects. The feasibility of treating POME in a closed dark fermentation (DF) system to replace the existing inefficient open ponding treatment has been thoroughly investigated. Theoretically, the maximum H₂ yield obtained by DF process is 4 mol_H2/mol_glucose, however, it is not achievable due to the nature of POME. In this study, several enhancement methods for increasing H₂ yield and DF process stability were discussed. An apprehension into the different pre-treatment methods on POME including physicochemical, chemical and biological and their effects on the characteristics of POME including pH, temperature, sugar content, solid content, viscosity, nutrients and by-product toxicity on the biohydrogen production and effluent quality were reviewed. Various bioreactor designs were used for biohydrogen from POME, the modifications applied on the system design to increase the stability and productivity of POME treatment have been examined. Moreover, higher biohydrogen productivity could be obtained with the addition of nanoparticle nutrients and introducing genetically modified H₂-producing bacteria. Finally, further investigation in the future shall focus on the development of a more inclusive and efficient POME treatment via DF process that favours biohydrogen production, environmental benign and economically viable.     

Biohydrogen production from oil palm frond juice and sewage sludge by a metabolically engineered Escherichia coli strain

Biohydrogen is considered a promising and environmentally friendly energy source. Escherichia coli BW25113 hyaB hybC hycA fdoG frdc ldhA aceE has been previously engineered for elevated biohydrogen production from glucose. In this study, we show that this strain can also use biomass from oil palm frond (OPF) juice and sewage sludge as substrates. Substrate improvement was accomplished when hydrogen productivity increased 8-fold after enzymatic treatment of the sludge with a mixture of amylase and cellulase. The OPF juice with sewage sludge provided an optimum carbon/nitrogen ratio since the yield of biohydrogen increased to 1.5 from 1.3 mol H₂/mol glucose compared to our previous study. In this study, we also reveal that our engineered strain improved 200-fold biohydrogen productivity from biomass sources compared to the unmodified host. In conclusion, we determined that our engineered strain can use biomass as an alternative substrate for enhanced biohydrogen production.     

Start-up study of biohydrogen production from palm oil mill effluent in a lab-scale up-flow anaerobic sludge blanket fixed-film reactor

A start-up study of lab-scale up-flow anaerobic sludge blanket fixed-film reactor (UASFF) was conducted to produce biohydrogen from palm oil mill effluent (POME). The reactor was fed with POME at different hydraulic retention time (HRT) and organic loading rate (OLR) to obtain the optimum fermentation time for maximum hydrogen yield (HY). The results showed the HY, volumetric hydrogen production rate (VHPR), and COD removal of 0.5–1.1 L H₂/g COD_consumed, 1.98–4.1 L H₂ L^?1 day^?1, and 33.4–38.5%, respectively. The characteristic study on POME particles was analyzed by particle size distribution (PSD), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). The microbial Shannon and Simpson diversity indices and Principal Component Analysis assessed the alpha and beta diversity, respectively. The results indicated the change of bacterial community diversity over the operation, in which Clostridium sensu stricto 1 and Lactobacillus species were contributed to hydrogen fermentation.     

Biohydrogen production from pentose-rich oil palm empty fruit bunch molasses: A first trial

Oil palm empty fruit bunch (OPEFB) was pretreated by local plantation industry to increase the accessibility towards its fermentable sugars. This pretreatment process led to the formation of a dark sugar-rich molasses byproduct. The total carbohydrate content of the molasses was 9.7 g/L with 4.3 g/L xylose (C₅H₁₀O₅). This pentose-rich molasses was fed as substrate for biohydrogen production using locally isolated Clostridium butyricum KBH1. The effect of initial pH and substrate concentration on the yield and productivity of hydrogen production were investigated in this study. The best result for the fermentation performed in 70 mL working volume was obtained at the initial reaction condition of pH 9, 150 rpm, 37 °C and 5.9 g/L total carbohydrate. The maximum hydrogen yield was 1.24 mol H₂/mol pentose and the highest productivity rate achieved was 0.91 mmol H₂/L/h. The optimal pH at pH 9 was slightly unusual due to the presence of inhibitors, mainly furfural. The furfural content decreased proportionally as pH was increased. The optimal experiment condition was repeated and continued in fermentation volume of 200 mL. The maximum hydrogen yield found for this run was 1.21 mol H₂/mol pentose while the maximum productivity was 1.1 mmol H₂/L/h. The major soluble metabolites in the fermentation were n-butyric acid and acetic acid.     

An overview of empty fruit bunch from oil palm as feedstock for bio-oil production

Empty fruit bunch (EFB) from oil palm is one of the potential biomass to produce biofuels like bio-oil due to its abundant supply and favorable physicochemical characteristics. Confirming the assertion, this paper presents an overview of EFB as a feedstock for bio-oil production. The fundamental characteristics of EFB in terms of proximate analysis, ultimate analysis and chemical composition, as well as the recent advances in EFB conversion processes for bio-oil production like pyrolysis and solvolysis are outlined and discussed. A comparison of properties in terms of proximate analysis, ultimate analysis and fuel properties between the bio-oil from EFB and petroleum fuel oil is included. The major challenges and future prospects towards the utilization of EFB as a useful resource for bio-oil production are also addressed.     

Production of glucose from oil palm trunk and sawdust of rubberwood and mixed hardwood

Disposing of solid waste and demand of fossil fuel have become the great challenges in the 21st century. Malaysia as one of the top producers of palm oil and wooden furniture in the world is well positioned to take the challenge of the reuses of its enormous output of lignocellulosic biomass such as oil palm trunk, sawdust of rubberwood and sawdust of mixed hardwood generated from palm oil and furniture industries. Before these lignocellulosic biomasses can be used to produce fuel and major chemicals which are normally derived from petroleum, lignocellulosic materials have to be converted to glucose. Hence, it is a need to investigate the conversion efficiency and to determine the optimum conditions for the conversion of lignocellulosic materials to glucose. This present work is aimed to investigate the potential use of oil palm trunk, rubberwood sawdust and mixed hardwood sawdust as an alternative feedstock for lignocellulosic glucose production. This research also served to identify the optimum two-stage concentrated acid hydrolysis condition that can convert these three lignocellulosic biomasses to glucose efficiently. Two stages concentrated sulfuric acid hydrolysis process using different acid concentration and reaction time were performed on those lignocellulosic biomass samples. The optimum results for oil palm trunk, rubberwood and mixed hardwood sawdust were obtained by using 60% acid concentration reacted for 30 min during 1st stage hydrolysis and subsequently followed by another 60 min reaction time with 30% acid concentration during the 2nd stage hydrolysis. The results, showed that oil palm trunk has a higher glucose conversion yield than those of rubberwood sawdust and mixed hardwood sawdust.     

Optimization of biohydrogen production from sweet sorghum syrup using statistical methods

This study employed statistically based experimental designs to optimize fermentation conditions for hydrogen production from sweet sorghum syrup by anaerobic mixed cultures. Initial screening of important factors influencing hydrogen production, i.e., total sugar, initial pH, nutrient solution, iron (II) sulphate (FeSO₄), peptone and sodium bicarbonate was conducted by the Plackett–Burman method. Results indicated that only FeSO₄ had statistically significant (P ≤ 0.005) influences on specific hydrogen production (P_s) while total sugar and initial pH had an interdependent effect on P_s. Optimal conditions for the maximal P_s were 25 g/L total sugar, 4.75 initial pH and 1.45 g/L FeSO₄ in which P_s of 6897 mL H₂/L was estimated. Estimated optimum conditions revealed only 0.04% difference from the actual P_s of 6864 mL H₂/L which suggested that the optimal conditions obtained can be practically applied to produce hydrogen from sweet sorghum syrup with the least error.