Analysis Package P15 : Uronic Acids

This study presents a method for effective pectin extraction from the laminae of three tobacco varieties as a means of biomass valorisation. Two pre-treatment methods (cold ethanol vs. accelerated solvent extraction [ASE] with ethanol) were compared for their capacities to produce a high pectin yield. Enzymatic extraction of pectin was also tested as a green extraction procedure and compared to the acid extraction approach. The optimisation experiments revealed that cold ethanol extraction followed by acid hydrolysis is the most convenient method for pectin extraction; the optimal set of conditions for hydrolysis were identified as 90°C, pH 1.5, and 4 h of extraction. Applying these optimised conditions to the three Nicotiana rustica tobacco varieties yielded pectin recoveries of 66.2%, 57.8%, and 56.7% from the NRT63, Bakoum Miena, and NRT61 samples, respectively. Tobacco pectins were found to have a medium molecular weight and low methoxy content. These results highlight the potential of tobacco residues as feedstock for to produce pectin with dietary applications.

Knowing the accurate composition of biomass is of crucial importance in order to assess and decide on the use and processes to be applied to specific biomass types. In this study, the composition of the lignocellulosic constituents present in forestry, agricultural and underutilised waste residues was assessed. Considering the increased interest on hemicellulose fractions for application in biomaterials and biomolecules, large emphasis has been given in detailing the monomeric constituents of the hemicellulose polymer. Lignin and cellulose, the two other major components of lignocellulosic biomass, were analysed and correlated with the trends in the other constituents. In the samples analysed, the total structural sugars content ranged from 26.0 to 67.5% of the biomass dry weight, indicating high variation between different feedstock and fractions. Hemicellulose concentration and composition also varied significantly (from 38.8% in birch (Betula Pendula Roth) foliage to 22.0 % in rice (Oryza sativa L.) straw) between the feedstock types and within the same feedstock type between different species and different fractions. The extractives content varied greatly between the different species (from 2.66 % to 30.47 % of the biomass dry weight) with high contents in certain fractions of feedstock suggesting more detailed compositional analysis of these extracts is warranted.

In this study, 18 animals were fed two forage-based diets: red clover (RC) and grass silage (GS), in a crossover-design experiment in which methane (CH4) emissions were recorded in respiration chambers. Rumen samples obtained through naso-gastric sampling tubes were analysed by NMR. Methane yield (g/kg DM) was significantly lower from animals fed RC (17.8 +/- 3.17) compared to GS (21.2 +/- 4.61) p = 0.008. In total 42 metabolites were identified, 6 showing significant differences between diets (acetate, propionate, butyrate, valerate, 3-phenylopropionate, and 2-hydroxyvalerate). Partial least squares discriminant analysis (PLS-DA) was used to assess which metabolites were more important to distinguish between diets and partial least squares (PLS) regressions were used to assess which metabolites were more strongly associated with the variation in CH4 emissions. Acetate, butyrate and propionate along with dimethylamine were important for the distinction between diets according to the PLS-DA results. PLS regression revealed that diet and dry matter intake are key factors to explain CH4 variation when included in the model. Additionally, PLS was conducted within diet, revealing that the association between metabolites and CH4 emissions can be conditioned by diet. These results provide new insights into the methylotrophic methanogenic pathway, confirming that metabolite profiles change according to diet composition, with consequences for CH4 emissions.

Acetone organosolv fractionation of beech and birch wood at the lab-scale results in high sugar yields from the (hemi)cellulose and the isolation of a high-purity lignin. In this study, the process is scaled up to validate the technology at the pilot scale using industrial-size beech and birch wood chips and low liquid-to-solid ratios as a next step toward commercialization. Translation of the fractionation process to the pilot-scale showed a similar performance as compared to the lab-scale processing with a good conversion of the wood polymeric pentoses to mostly monomeric sugars and a high delignification. Continuous lignin precipitation by solvent evaporation using the LigniSep process resulted in the formation of nonsticky lignin aggregates with a good filterability. The improved lignin yields and advanced process design as compared to the traditional dilutive lignin precipitation approaches are likely to translate to a better process economy. The pulp washing efficiency and the recovery of (nonprecipitable) lignin from the aqueous hemicellulose stream still need to be improved for an efficient process design. However, the fractionation performance and high product concentrations in the spent liquor provide an excellent start position for improved process design at the commercial scale.

Pretreatments of lignocellulosic biomass prior to fast pyrolysis need to give a better yield and quality of pyrolysis oil and be practical to implement at a commercial scale. This study demonstrated, at a large pilot scale, that thermomechanical refining can reduce the particle size, hemicellulose content, and mineral content of pine wood chips, leading to improved yields of carbohydrate-derived chemicals on fast pyrolysis. Additionally, a hemicellulose-rich byproduct can be generated during the pretreatment for separate valorization. The impact of different presteaming times, citric acid infusion, and disc refining on the yield and composition of the pyrolysis oil was studied. Presteaming of citric acid-infused wood chips at 173 C for 3 min and refining to wood fiber proved most effective in improving the yield of pyrolysis oil organics, including the valuable biochemicals levoglucosan and hydroxyacetaldehyde, while reducing the yields of low-value char and noncondensable gases.