Unlocking pilot-scale green diesel production from microalgae.

Microalgae have emerged as a promising source of biomass to produce renewable biofuels due to their ability to synthesize high-energy density compounds of commercial interest. This study proposes an approach for pilot-scale oil extraction, purification by fractional distillation, hydrocarbon characterization by gas chromatography coupled to mass spectrometry (GC-MS), evaluation of physicochemical parameters of the produced hydrocarbons, preliminary cost analysis, and challenges and future opportunities for green diesel on a commercial scale. Here, the microalgae Tetradesmus obliquus was cultivated in 12 m³ photobioreactors using biodigested swine waste as a culture medium. The resulting biomass was subjected to drying and harvesting, followed by oil extraction using a hot solvent extraction method, followed by distillation to purify the compounds. Three different extraction and distillation experiments were conducted, each using different solvent combinations. The results obtained revealed that extraction with a solvent blend, composed of hexane and ethanol, provided more significant yields compared to extraction with pure hexane. GC-MS analysis showed the presence of alkanes and alkenes in the oil samples, and the proportion of solvent used in the extraction directly influenced the production of alkanes. Additionally, specific hydrocarbons such as 4-methyl-1-decene, 8-heptadecene, 1-pentadecene, 9-heneicosene, and 2-dodecene were identified. The evaluation of the physicochemical parameters demonstrated that the calorific value of the distilled oil samples is within the range of typical values for petroleum diesel. However, it was observed that the distilled oil samples had higher sulfur content compared to conventional diesel. Regarding the cost analysis, it was found that it varies depending on the experimental conditions. In particular, the process using a solvent mixture of 70% hexane and 30% ethanol proved to be more economical than the others, since it extracted a greater quantity of oil with a lower initial biomass requirement. In summary, this microalgae-derived hydrocarbon production process is promising and offers insights for compound purification and future biofuel applications.

Development of a Microwave-Assisted Bench Reactor for Biomass Pyrolysis Using Hybrid Heating.

Microwave-assisted pyrolysis (MAP) is a cutting-edge technology that converts biomass into fuels, chemicals, and materials. In this study, an Arduino was used to control and automate a MAP system built from a microwave oven with a cordierite chamber filled with silicon carbide. Sugar cane bagasse was pyrolyzed at 250, 350, 450, and 550 °C to validate the MAP system and obtain pyrolytic products with different yields and chemical compositions. Lower temperatures led to high biochar yields, but the highest surface area of 25.14 m2 g-1 was only achieved at 550 °C. By contrast, higher temperatures favored the recovery of pyrolysis liquids. BET and scanning electron microscopy analyses revealed a porous biochar structure, while Fourier transform infrared spectroscopy analysis showed that the availability of functional groups on the biochar surface decreased with an increase in pyrolysis temperature. GC-MS analysis quantified valuable low molecular mass compounds in pyrolysis liquids, including aldehydes, ketones, phenols, and alcohols. With its unprecedented hybrid heating device, the MAP system promoted suitable heating rates (31.9 °C min-1) and precise temperature control (only 19 °C of set point variation), generating pyrolysis products devoid of microwave susceptor interferences. Therefore, MAP provided a rapid, safe, and efficient means of depolymerizing biomass, thus holding promise for biorefinery applications.

Impact of cellulose properties on enzymatic degradation by bacterial GH48 enzymes: Structural and mechanistic insights from processive Bacillus licheniformis Cel48B cellulase.

Processive cellulases are highly efficient molecular engines involved in the cellulose breakdown process. However, the mechanism that processive bacterial enzymes utilize to recruit and retain cellulose strands in the catalytic site remains poorly understood. Here, integrated enzymatic assays, protein crystallography and computational approaches were combined to study the enzymatic properties of the processive BlCel48B cellulase from Bacillus licheniformis. Hydrolytic efficiency, substrate binding affinity, cleavage patterns, and the apparent processivity of bacterial BlCel48B are significantly impacted by the cellulose size and its surface morphology. BlCel48B crystallographic structure was solved with ligands spanning -5 to -2 and +1 to +2 subsites. Statistical coupling analysis and molecular dynamics show that co-evolved residues on active site are critical for stabilizing ligands in the catalytic tunnel. Our results provide mechanistic insights into BlCel48B molecular-level determinants of activity, substrate binding, and processivity on insoluble cellulose, thus shedding light on structure-activity correlations of GH48 family members in general.

Multiple response optimization of alkaline pretreatment of sisal fiber (Agave sisalana) assisted by ultrasound.

A procedure for the alkaline pretreatment of sisal fiber assisted by ultrasound was optimized to obtain a higher solubilization of hemicellulose and the removal of lignin with cellulose fraction maintenance. A full factorial design 23 was used for the evaluation of the effects of the variables (sonication time, NaOH concentration, and sonication amplitude) on the pretreatment. The optimal values for the variables using the Doehlert matrix for the sonication time, NaOH concentration, and sonication amplitude were 27 min, 4.1% (m/v), and 50%, respectively. The X-ray diffractometry and scanning electron microscopy analyses, after pretreatment, showed changes in chemical structure and morphology due to the removal of 82% of hemicellulose and 86% of lignin from sisal fiber. The soft reaction conditions and relatively short times demonstrated the effectiveness of the combined action of ultrasound with alkaline pretreatment to improve the accessibility to cellulose in this important step of the ethanol production process from biomass.

Molecular and structural characterization of the biosurfactant produced by Pseudomonas aeruginosa DAUPE 614.

Pseudomonas aeruginosa DAUPE 614 produced rhamnolipids (3.9gL(-1)) when cultivated on a medium containing glycerol and ammonium nitrate. These rhamnolipids reduced the surface tension of water to 27.3mNm(-1), with a critical micelle concentration of 13.9mgL(-1). The maximum emulsification index against toluene was 86.4%. The structure of the carbohydrate moiety of the glycolipid was determined by gas chromatography-mass spectroscopy (GC-MS) analysis allied to electrospray ionization mass spectrometry and nuclear magnetic resonance (NMR) 1D, 2D (13)C, (1)H spectroscopy. The hydroxyl fatty acids were analyzed by GC-MS as hydroxy-acetylated fatty acid methyl ester derivatives. The positions of the fatty acids in the lipid moiety were variable, with 6 mono-rhamnolipid homologues (Rha-C(10)-C(10); Rha-C(10)-C(8); Rha-C(8)-C(10); Rha-C(10)-C(12:1); Rha-C(12)-C(10); Rha-C(10)-C(12)) and 6 di-rhamnolipid homologues (Rha(2)-C(10)-C(10); Rha(2)-C(10)-C(8); Rha(2)-C(8)-C(10); Rha(2)-C(10)-C(12:1); Rha(2)-C(12)-C(10); Rha(2)-C(10)-C(12)). The ratio of Rha(2)-C(10)-C(10) to Rha-C(10)-C(10) was higher than has been reported in previous studies. Our methodology allowed us to distinguish between the isomeric pairs Rha-C(10)-C(8)/Rha-C(8)-C(10), Rha-C(10)-C(12)/Rha-C(12)-C(10), Rha(2)-C(10)-C(8)/Rha(2)-C(8)-C(10) and Rha(2)-C(12)-C(10)/Rha(2)-C(10)-C(12). For each isomeric pair, the congener with the shorter chain adjacent to the sugar was always more abundant than the congener with longer chain.

Multivariate monitoring of soybean oil ethanolysis by FTIR.

In this work, an analytical procedure was developed to monitor the ethanolysis of degummed soybean oil (DSO) using Fourier-transformed mid-infrared spectroscopy (FTIR) and methods of multivariate analysis such as principal component analysis (PCA) and partial least squares regression (PLS). The triglycerides (reagents) and ethyl esters (products) involved in ethanolysis were shown to have similar FTIR spectra. However, when the FTIR spectra derived from seven standard mixtures of triolein and ethyl oleate were treated by PCA at the region that represents the CO stretching vibration of ester groups (1700-1800cm(-1)), only two principal components (PC) were shown to capture 99.95% of the total spectral variance (92.37% for the former and 7.58% for the latter PC). This observation supported the development of a multivariate calibration model that was based on the PLS regression of the FTIR data. The prevision capability of this model was measured against 40 reaction aliquots whose ester content was previously determined by size exclusion chromatography. Only small discrepancies were observed when the two experimental data sets were treated by linear regression (R(2)=0.9837) and these deviations were attributed to the occurrence of non-modeled transient species in the reaction mixture (reaction intermediates), particularly at short reaction times. Therefore, the FTIR/PLS model was shown to be a fast and accurate method to predict reaction yields and to follow the in situ kinetics of soybean oil ethanolysis.

Fractionation of Eucalyptus grandis chips by dilute acid-catalysed steam explosion.

Steam explosion of Eucalyptus grandis has been carried out under various pretreatment conditions (200-210 degrees C, 2-5 min) after impregnation of the wood chips with 0.087 and 0.175% (w/w) H2SO4. This study, arranged as a 2(3) factorial design, indicated that pretreatment temperature is the most critical variable affecting the yield of steam-treated fractions. Pretreatment of 0.175% (w/w) H2SO4-impregnated chips at 210 degrees C for 2 min was the best condition for hemicellulose recovery (mostly as xylose) in the water soluble fraction, reaching almost 70% of the corresponding xylose theoretical yield. By contrast, lower pretreatment temperatures of 200 degrees C were enough to yield steam-treated substrates from which a 90% cellulose conversion was obtained in 48 h, using low enzyme loadings of a Celluclast 1.5 1 plus Novozym 188 mixture (Novo Nordisk). Release of water-soluble chromophores was monitored by UV spectroscopy and their concentration increased with pretreatment severity. The yield of alkali-soluble lignin increased at higher levels of acid impregnation and pretreatment temperatures. Thermoanalysis of these lignin fractions indicated a pattern of lignin fragmentation towards greater pretreatment severities but lignin condensation prevailed at the most drastic pretreatment conditions.