• Energy Research

ABSTRACTRefined palm kernel oil was trans-esterified with ethanol to produce fatty acid ethyl esters. The medium-chain fatty acid ethyl ester (bio-kerosene) was fractionated from the bottom fractio...

Rhodotorula paludigena CM33 is an oleaginous yeast that has been demonstrated to accumulate substantial quantities of intracellular lipids and carotenoids. In this study, crude glycerol, a by-product of biodiesel production, was used as a carbon source to enhance the accumulation of lipids and carotenoids in the cells. The culture conditions were first optimized using response surface methodology, which revealed that the carotenoid concentration and lipid content improved when the concentration of crude glycerol was 40 g/L. Different fermentation conditions were also investigated: batch, repeated-batch, and fed-batch conditions in a 500 L fermenter. For fed-batch fermentation, the maximum concentrations of biomass, lipids, and carotenoids obtained were 46.32 g/L, 37.65%, and 713.80 mg/L, respectively. A chemical-free carotenoid extraction method was also optimized using high-pressure homogenization and a microfluidizer device. The carotenoids were found to be mostly beta-carotene, which was confirmed by HPLC (high pressure liquid chromatography), LC-MS (liquid chromatography-mass spectrometry), and NMR (nuclear magnetic resonance). The results of this study indicate that crude glycerol can be used as a substrate to produce carotenoids, resulting in enhanced value of this biodiesel by-product.

AbstractAn oleaginous yeast Rhodotorula paludigena CM33 was pyrolyzed for the first time to produce bio-oil and biochar applying a bench-scale reactor. The strain possessed a high lipid content with the main fatty acids similar to vegetable oils. Prior to pyrolysis, the yeast was dehydrated using a spray dryer. Pyrolysis temperatures in the range of 400–600 °C were explored in order to obtain the optimal condition for bio-oil and biochar production. The result showed that a maximum bio-oil yield of 60% was achieved at 550 °C. Simulated distillation gas chromatography showed that the bio-oil contained 2.6% heavy naphtha, 20.7% kerosene, 24.3% biodiesel, and 52.4% fuel oil. Moreover, a short path distillation technique was attempted in order to further purify the bio-oil. The biochar was also characterized for its properties. The consequence of this work could pave a way for the sustainable production of solid and liquid biofuel products from the oleaginous yeast.

AbstractCassava pulp (CP), a by‐product of the tapioca starch industry, has been recognized as a high potential substrate for bio‐gas production due to its high carbon content. In this work, co‐digestion between CP and distiller stillage (DS) was investigated with the main objective to improve the system stability as well as to enhance the biogas production. The effect of five different CP:DS ratios including 1:0, 1:0.5, 1:1, 0.5:1, and 0:1 based on volatile solids (VS) was carried out. The result showed that the co‐digestion of CP and DS is a promising approach for increasing the cumulative methane yield by 65.57%–222.19% compared to the digestion of CP alone. The highest methane yield of 685.10 ml/g VS was obtained at the CP:DS of 1:1. The bacterial and archaeal communities were analyzed by denaturing gradient gel electrophoresis. The bacterial community of CP:DS ratio was dominated by Bacteroidetes, Firmicutes, and Chloroflexi phylum whilst Methanosarcina (Methanosarcina barkeri) dominated the methanogenic archaeal community. This work demonstrated the adaptation of co‐digestion resulting in a higher methane production with a higher stability of the system. The result could pave a way for a highly efficient co‐digestion system in a larger scale biogas production.

This study examines the effects of engine compression ratio, load, and biofuel composition on performance, combustion, and emissions. The experimental setup includes testing different compression ratios (16, 17, 18) and loads (25 %, 50 %, 75 % torque) at a fixed speed of 1500 rpm, using Thai standard diesel as the control fuel. Biofuel variations tested include neat biodiesel, neat biokerosene, and blends of 30 % biokerosene with 70 % biodiesel and 50 % biokerosene with 50 % biodiesel. The results show that an increased compression ratio enhances combustion efficiency, reduces brake specific fuel consumption, and improves brake thermal efficiency, although it also leads to higher nitrogen oxide emissions. Biofuels improve brake thermal efficiency due to their higher oxygen content. However, the increased viscosity of biodiesel can hinder fuel atomization, resulting in higher emissions. In contrast, biokerosene improves brake thermal efficiency by facilitating earlier combustion and reducing emissions. Performance is primarily affected by load, while emissions are influenced by both biokerosene content and load. Gradient boosting models and optimization techniques, such as the non-dominated sorting genetic algorithm III (NSGA-III) and adaptive geometry estimation-based multi-objective evolutionary algorithms (AGE-MOEA), produce consistent results, with AGE-MOEA identifying denser optimal points. The findings suggest that optimal biokerosene blends ranging from 20 % to 40 %, across all compression ratios and loads of 50 %–75 %, provide valuable insights for advancing sustainable fuel utilization practices in automotive vehicles.

La contamination du sol par des substances huileuses a conduit à plusieurs problèmes environnementaux. Ces travaux se sont concentrés sur l'isolement et la caractérisation des micro-organismes qui possèdent la capacité de dégrader l'huile de Jatropha, un stock d'alimentation de production de biodiesel, dans des conditions anaérobies. Les souches isolées actives ont été testées pour leurs caractéristiques morphologiques, physiologiques et génotypiques. Sur la base de l'analyse de la séquence d'ARNr 16S, Enterococcus faecalis et Burkholderia cenocepacia W-1 ont été sélectionnés en raison de leur capacité à produire de grandes Des études supplémentaires ont été menées pour la dégradation de l'huile en utilisant un minimum de milieu salin M9 supplémenté avec de l'huile de Jatropha à 1% comme seule source de carbone. Le test d'activité lipolytique a montré que l'activité la plus élevée était obtenue à 532 U/L. En outre, l'analyse GC/MS a révélé que différents composés de l'espace de tête et du surnageant comprenaient plusieurs hydrocarbures. Cependant, les acides gras libres formés au cours de l'activité hydrolytique ont entraîné la diminution du pH et également retardé la croissance bactérienne probablement en raison de la toxicité des acides gras sur les cellules. La conséquence de cette étude est le bénéfice de la réduction des problèmes environnementaux dus à la contamination par l'huile de Jatropha ainsi que obtenu biocarburants gazeux utiles. La contaminación del suelo por sustancias oleosas condujo a varios problemas ambientales. Este trabajo se centró en el aislamiento y la caracterización de microorganismos que poseen la capacidad de degradar el aceite de Jatropha, una materia prima de producción de biodiésel, en condiciones anaeróbicas. Las cepas aisladas activas se probaron para determinar las características morfológicas, fisiológicas y genotípicas. Con base en el análisis de la secuencia de ARNr 16S, se seleccionaron Enterococcus faecalis y Burkholderia cenocepacia W-1 debido a su capacidad para producir grandes zonas. Se realizaron estudios adicionales para la degradación del aceite utilizando medios de sal M9 mínimos complementados con aceite de Jatropha al 1% como única fuente de carbono. El ensayo de actividad lipolítica mostró que la actividad más alta se obtuvo a 532 U/L. Además, el análisis de GC/MS reveló que los diferentes compuestos del espacio de cabeza y el sobrenadante incluían varios hidrocarburos. Sin embargo, los ácidos grasos libres formados durante la actividad hidrolítica resultaron en la disminución del pH y también retrasaron el crecimiento bacteriano probablemente debido a la toxicidad de los ácidos grasos en las células. La consecuencia de este estudio es el beneficio de la reducción de los problemas ambientales de la contaminación por aceite de Jatropha, así como la obtención biocombustibles gaseosos útiles. Ground contamination by oily substances led to several environmental issues.This work focused on the isolation and characterization of micro-organisms which possess the capability of degrading Jatropha oil, a feed stock of biodiesel production, under anaerobic condition.The active isolated strains were tested for morphological, physiological and genotypic characteristics.Based on 16S rRNA sequence analysis, the Enterococcus faecalis and Burkholderia cenocepacia W-1 were selected due to their ability to produce large clear zones.Further studies were carried out for oil degradation using minimal M9 salt media supplemented with 1% Jatropha oil as the sole carbon source.Lipolytic activity assay showed that the highest activity was obtained at 532 U/L.In addition, GC/MS analysis revealed that different compounds from the head space and supernatant included several hydrocarbons.However, free fatty acids formed during hydrolytic activity resulted in the decrease of pH, and also retarded bacterial growth probably due to the toxicity of the fatty acids on the cells.The consequence of this study is the benefit of reduced environmental problems from Jatropha oil contamination as well as obtained useful gaseous biofuels. أدى التلوث الأرضي بالمواد الزيتية إلى العديد من القضايا البيئية. ركز هذا العمل على عزل وتوصيف الكائنات الحية الدقيقة التي تمتلك القدرة على تحلل زيت الجاتروفا، وهو مخزون علف لإنتاج الديزل الحيوي، في ظل ظروف لاهوائية. تم اختبار السلالات المعزولة النشطة بحثًا عن الخصائص المورفولوجية والفسيولوجية والنمطية الوراثية. استنادًا إلى تحليل تسلسل الحمض النووي الريبي الريبوزي 16S، تم اختيار المكورات المعوية البرازية و Burkholderia cenocepacia W -1 بسبب قدرتها على إنتاج كمية كبيرة واضحة المناطق. أجريت المزيد من الدراسات لتدهور الزيت باستخدام الحد الأدنى من الوسائط المالحة M9 المكملة بزيت الجاتروفا بنسبة 1 ٪ كمصدر وحيد للكربون. أظهر فحص النشاط المحللي للدهون أنه تم الحصول على أعلى نشاط عند 532 وحدة/لتر. بالإضافة إلى ذلك، كشف تحليل GC/MS أن المركبات المختلفة من مساحة الرأس والطفرة الطافية شملت العديد من الهيدروكربونات. ومع ذلك، أدت الأحماض الدهنية الحرة المتكونة أثناء نشاط التحلل المائي إلى انخفاض درجة الحموضة، وكذلك تأخر نمو البكتيريا ربما بسبب سمية الأحماض الدهنية على الخلايا. نتيجة هذه الدراسة هي فائدة تقليل المشاكل البيئية من تلوث زيت الجاتروفا وكذلك الحصول عليها وقود حيوي غازي مفيد.

Sixty-seven yeast strains were isolated from castor beans then their endogenous lipids were stained by Nile Red (NR) fluorescence dye, and flow cytometry was used to obtain a strain with a high relative mean fluorescence intensity (MFI) value. The highest MFI value was obtained for strain CM33, which produced a maximum lipid content of 20.8 % dry cell weight (DCW). Based on the sequence of the ITS-5.8S-ITS rDNA and D1/D2 26S rDNA regions, CM33 showed 99 % identity with Rhodotorula paludigena. The potential of CM33 to assimilate various carbon sources was examined by growth on minimal media using glucose, glycerol, sucrose or xylose. CM33 was grown in glucose-based medium for 96 h and exhibited a maximum lipid content of 23.9 % DCW. Furthermore, when cells were cultured on molasses waste, their biomass, lipid content and lipid concentration reached 16.5 g/L, 37.1 % DCW and 6.1 g/L, respectively. These results demonstrated the potential of R. paludigena CM33 to contribute to a value-added carbon chain by converting renewable waste materials for biolipid production.