Optimization of lignin extraction from bamboo by ultrasound-assisted organosolv pretreatment

Lignin extraction from acacia wood: Crafting deep eutectic solvents with a systematic D-optimal mixture-process experimental design

Lignin is a complex biopolymer whose efficient extraction from biomass is crucial for various applications. Deep eutectic solvents (DES), particularly natural-origin DES (NADES), have emerged as promising systems for lignin fractionation and separation from other biomass components. While ternary DES offer enhanced fractionation performance, the role of each component in these mixtures remains unclear. In this study, the effects of adding tartaric acid (Tart) or citric acid (Cit) to a common binary DES mixture composed of lactic acid (Lact) and choline chloride (ChCl) were investigated for lignin extraction from acacia wood. Ternary Cit-based DES showed superior performance compared to Tart-based DES. Using a combined mixture-process D-Optimal experimental design, the Lact:Cit:ChCl DES composition and extraction temperature were optimized targeting maximum lignin yield and purity. The optimal conditions (i.e., Lact:Cit:ChCl, 0.6:0.3:0.1 molar ratio, 140 °C) resulted in a lignin extraction yield of 99.63 ± 1.24 % and a lignin purity of 91.45 ± 1.03 %. Furthermore, this DES exhibited feasible recyclability and reusability without sacrificing efficiency.

Valorization of Lignocellulose with One-Step Acidified Monophasic Phenoxyethanol Fractionation

Effective fractionation of lignocelluosic biomass and subsequent valorization of all three major components under mild conditions were achieved. Pretreatment with acidified monophasic phenoxyethanol (EPH) efficiently removed 92.6 % lignin and 80 % xylan from poplar at 110 °C in 60 min, yielding high-value EPH-xyloside, EPH-modified lignin (EPHL), and a solid residue nearly purely composed of carbohydrates. After removing the grafted acetyl groups using 1 % NaOH at 50 °C, the highest enzymatic digestibility reached 92.3 %. EPHL could be recovered in high yield and purity with an uncondensed structure, while xylose was converted to EPH-xyloside, a potential precursor in biomedical industries. Additionally, the acidified monophasic EPH solvent could effectively fractionate biomass from species other than hardwood, achieving over 70 % delignification from recalcitrant pinewood under the same mild conditions, demonstrating the high potential of monophasic EPH pretreatment.

Extraction of super high-yield lignin-carbohydrate complexes from rice straw without compromising cellulose hydrolysis

Lignin-carbohydrate complexes (LCC) that exhibit both structural advantages of lignin and carbohydrates are promising amphiphilic biopolymers, but the extraction is challenged by its liable chemical bond cleavage between lignin and carbohydrates. This work proposed a facile chemical route to integrating the production of water-insoluble (WIS LCC) and water-soluble LCC (WS LCC) into the emerging deep eutectic solvent (DES) biorefinery at mild conditions. The tailored mechanochemical fractionation process of ball milling assisted aqueous alkaline DES could extract 24.2 % LCC in total, with the co-production of a highly hydrolysable cellulose fraction (98.7 % glucose conversion). The resulting LCC exhibited considerably high contents of β-O-4, phenyl glycoside, and ferulic acid linkage bonds. When 100 g starting straw was subjected to this technique route, 9.1 g WIS LCC, 15.1 g WS LCC and 45.5 g glucose were cascaded produced. It was proposed that the selective disruption of hydrogen bonding entangled network and the quasi-state dissolution of the whole biomass allowed the subsequent cascade fractionation of WIS LCC, WS LCC and highly hydrolysable cellulose through solution property adjustment. This work showed a promising approach for LCC production with high yield without compromising cellulose conversion potential, which has been challenging in the current lignocellulose biorefinery.

Delignification of the cotton stalk and ginning mill waste via EnZolv pretreatment and optimization of process parameters using response surface methodology (RSM)

The present study aimed to add value to cotton waste biomass using a more eco-friendly process, EnZolv which delignifies cotton stalk and cotton ginning mill waste. A maximum delignification of 68.68% and 65.51% was obtained using pre-optimized EnZolv parameters in cotton stalk (CS) and ginning mill waste (GMW), respectively. Optimized EnZolv process removed 78.68% of lignin in CS using Response Surface Methodology (RSM) in Box-Behnken design at 0% moisture content, 50 U laccase g-1 of biomass, 5 h incubation time, 50 ⁰C incubation temperature, and 150 rpm shaking speed. Similarly, RSM-based delignification of 70.53% in GMW was achieved under the optimized EnZolv conditions of 98.75 % moisture content, 41.59 U laccase g-1 of biomass, 9.3 h incubation time, 46.15 ⁰C incubation temperature, and 150 rpm shaking speed.

High efficient adsorption of W(VI) with a novel lignin-based biosorbent functionalized with Zn2+ and polyamine

Functionalized lignin-based biosorbent has become popular in wastewater treatment and extraction of valuable metals. Amination and metallization modification can effectively improve the adsorption performance of adsorbent. Zn2+/polyamine lignin for adsorption of W(VI) was synthesized by quaternization, amination and metallization from lignin with 3-chloro-2-hydroxypropyl trimethylammonium chloride, tetraethylenepentamine and ZnCl2. The adsorbent was characterized by SEM-EDS, FTIR and XRD. The adsorption performance of Zn2+/polyamine lignin for W(VI) was investigated in batch system. The adsorption mechanism was revealed by zeta potential, SEM-EDS and FTIR and XPS. It was shown that Zn2+/polyamine lignin exhibited great adsorption capacity at pH of 2, 25 °C, oscillation rate of 400 r/min, initial tungsten concentration of 700 mg·L-1 and adsorption time of 720 min. The maximum adsorption capacity of 0.5 g·L-1 Zn2+/polyamine lignin for W(VI) reached 488.28 mg·g-1. The adsorption followed Langmuir model and quasi-second-order kinetic model, indicating that the adsorption was monolayer homogeneous chemisorption. W(VI) was adsorbed through electrostatic attraction of hydrogen bond and Zn2+, ion exchange with Cl- and coordination with -NH2. The adsorption capacity reduced by only 6.47 % after seven cycles of adsorption-desorption, which indicated that Zn2+/polyamine lignin had a great application prospect.

Development of lignocellulosic biorefineries for the sustainable production of biofuels: Towards circular bioeconomy

The idea of environment friendly and affordable renewable energy resources has prompted the industry to focus on the set up of biorefineries for sustainable bioeconomy. Lignocellulosic biomass (LCB) is considered as an abundantly available renewable feedstock for the production of biofuels which can potentially reduce the dependence on petrochemical refineries. By utilizing various conversion technologies, an integrated biorefinery platform of LCB can be created, embracing the idea of the 'circular bioeconomy'. The development of effective pretreatment methods and biocatalytic systems by various bioengineering and machine learning approaches could reduce the bioprocessing costs, thereby making biomass-based biorefinery more sustainable. This review summarizes the development and advances in the lignocellulosic biorefineries from the LCB to the final product stage using various different state-of-the-art approaches for the progress of circular bioeconomy. The life cycle assessment which generates knowledge on the environmental impacts related to biofuel production chains is also summarized.