The formation of lignin-like structures by the degradation primarily of plant polysaccharides has been observed after the severe thermochemical acidic pretreatment of lignocellulosic biomass.

Deconstruction with low-cost ionic liquids (ionoSolv) is a promising method to pre-condition lignocellulosic biomass for the production of renewable fuels, materials and chemicals. This study investigated process intensification strategies for ionoSolv pretreatment of Miscanthus × giganteus with the low-cost ionic liquid triethylammonium hydrogen sulfate ([TEA] [HSO 4 ]) in the presence of 20 wt% water, using high temperatures and a high solid to solvent loading of 1 : 5 g/g. The temperatures investigated were 150, 160, 170 and 180°C. We discuss the effect of pretreatment temperature on lignin and hemicellulose removal, cellulose degradation and enzymatic saccharification yields. We report that very good fractionation can be achieved across all investigated temperatures, including an enzymatic saccharification yield exceeding 75% of the theoretical maximum after only 15 min of treatment at 180°C. We further characterised the recovered lignins, which established some tunability of the hydroxyl group content, subunit composition, connectivity and molecular weight distribution in the isolated lignin while maintaining maximum saccharification yield. This drastic reduction of pretreatment time at increased biomass loading without a yield penalty is promising for the development of a commercial ionoSolv pretreatment process.

Combinatorial pretreatments with a low holding temperature were developed in an effort to synergistically improve the carbohydrate output and lignin processability from corn stover.

Sequential organosolv fragmentation approach (SOFA) enhances the self-assembling process of high-quality lignin nanoparticles (LNPs) by tailoring the lignin chemistry in biorefineries.

Cooperative valorization of lignin and residual sugar has the potential to improve the sustainability and profitability of biorefineries.

Cinnamate esters have gained importance due to their unique antioxidant, flavor, and fragrance properties. Synergism of microwave irradiation and enzyme catalysis was investigated in transesterification of ethyl cinnamate and geraniol. Effects of different operating parameters such as biocatalyst, solvent, and temperature were first studied. An increase in initial rates up to 4.2-fold was observed under microwave irradiation vis-a-vis conventional heating. Further, the Taguchi L16 (4*4) orthogonal array design with four level-four variables and 16 run was employed for the optimization of parameters including enzyme loading, temperature, speed of agitation, and substrate mole ratio. Optimal conditions obtained via the Taguchi approach were as follows: enzyme loading, 60 mg; temperature, 65 °C; speed of agitation, 300 rpm; and substrate mole ratio, 1:2. The analysis of initial rate data established the validity of the ternary complex ordered bi-bi mechanism with inhibition by geraniol. The experimental data fitted very well with the model predictions.

Alkyl benzoate esters have gained importance due to their application in a variety of industries such as flavor, cosmetics, and pharmaceuticals. Effect of microwave irradiation in the enzymatic transesterification of methyl benzoate with different alcohols, viz., n-butanol, n-pentanol, n-hexanol, n-octanol, benzyl alcohol, isoamyl alcohol, and 2-ethyl-1-hexanol, was investigated. Synthesis of n-hexyl benzoate was chosen as the model reaction. Different enzymes such as Novozym 435, Lipozyme TL IM, Lipozyme RM IM, and Lipase AYS Amano were screened under microwave irradiation. Novozym 435 was the most active catalyst. To establish the kinetics and mechanism for Novozym 435 catalyzed transesterification of methyl benzoate with n-hexanol, the effects of various parameters affecting the conversion and rate of reaction were studied. Under microwave synergism, an increase in initial rates up to 6.5-fold was observed. Twenty millimoles of methyl benzoate and 10 mmol of n-hexanol in n-heptane with immobilized Candida antarctica lipase B, i.e., Novozym 435, as biocatalyst showed an optimal conversion of 97% at 60 °C in 6 h. Based on initial rate and progress curve data, the reaction was found to follow the ternary complex ordered bi–bi mechanism with inhibition by n-hexanol.

To make biorefineries sustainable, codesign of fractionation technologies and lignin valorization has been found to be essential. Combinatorial organosolv pretreatment (COP) was thus developed in an effort to efficiently produce sugars and improve lignin processability for the fabrication of lignin nanoparticles (LNPs). COP produced greater than a 90% glucose yield and 73% xylose yield, suggesting the improved sugar release from biomass. LNPs were fabricated from the lignin fractionated by COP via antisolvent precipitation. The smallest effective diameter (142 nm) of LNPs was obtained from COP using EtOH plus sulfuric acid. These LNPs possessed a lower polydispersity index and higher zeta potential, suggesting superior uniformity and greater stability. The lignin characterization results indicated that COP using EtOH plus sulfuric acid cleaved more β-O-4 and β–β linkages and produced lignin with a higher molecular weight and increased G-lignin and C5-substituted OH contents, suggesting the generation of condensed lignin. These modifications enhanced the hydrophobic interactions between lignins and thus enabled the fabrication of LNPs with a small particle size. COP using EtOH plus sulfuric acid also enriched total phenolic OH content and could promote the formation of a hydrogen-bonding network within LNPs. Together with a high zeta potential due to the increased phenolic OH and COOH groups, the stability of LNPs was thus enhanced. Overall, COP increased the sugar release from biomass and improved the lignin processability to facilitate the design of LNPs with satisfactory properties, which showed the potential to improve the lignin valorization and the sustainability of biorefineries.