Enhanced lignin extraction process from steam exploded corn stalk

Current roles of lignin for the agroindustry: Applications, challenges, and opportunities

Lignin has the potential to be used as an additive, coating agent, fertilizer, plant growth stimulator, and packaging material in the agroindustry due to its functional aromatic structure. The quantitative measurement of functional groups is a significant element of the research for lignin structure since they directly impact their optical, dispersion, and chemical properties. These physical and chemical properties of lignin strongly depend on its type and source and its isolation procedure. Thus, lignin provides numerous opportunities for the circular economy in the agroindustry; however, studying and resolving the challenges associated with its separation, purification, and modification is required. This review discusses the most recent findings on lignin use in agroindustry and historical facts about lignin. The properties of lignin and its roles as coating agents, pesticide carriers, plant growth stimulators, and soil-improving agents have been summarized. The emerging challenges in the field of lignin-based agroindustry are considered, and potential future steps to overcome these challenges are discussed.

Lignin from Morinda citrifolia leaves: Physical and chemical characterization, in vitro evaluation of antioxidant, cytotoxic, antiparasitic and ultrastructural activities

In this work, we investigated in vitro the antioxidant, cytotoxic and anti-leishmanial activities of a lignin extracted from the leaves of Morinda citrifolia. Initially, an analysis of the composition of the sheets was performed, then the lignin was obtained by alkaline delignification and characterized by different techniques: elemental analysis, FT-R, UV-vis, HSQC-NMR, thermal analysis, Py-GC/MS and by GPC. The results showed that the leaves had in their composition cellulose (31.29%), hemicellulose (25.01%), lignin (18.34%), extractives (14.39%) and ash (10.03%). The lignin extraction yield was 89.8%. The lignin obtained is of the GSH type with the following contents 79.39%, 13.58% and 7.03% respectively. Furthermore, it is low molecular weight and thermally stable. It had a phenolic content of 93.3 mg GAE/g and low antioxidant activity. In macrophage cytotoxicity assays, it presented a CC₅₀ of 31.0 μg/mL, showing less toxicity than amphotericin B. In assays against the promastigote forms of Leishmania amazonensis, lignin presented an IC₅₀ of 29.56 μg/mL, a less effective concentration than amphotericin B (IC₅₀ = 0.14 μg/mL). However, it was able to promote inhibition of the parasites, a fact confirmed by structural changes. These findings reinforce that M. citrifolia lignin is a promising macromolecule for use as an antiparasitic and antioxidant agent.

Advantages and Disadvantages of Bioplastics Production from Starch and Lignocellulosic Components

The accumulation of plastic wastes in different environments has become a topic of major concern over the past decades; therefore, technologies and strategies aimed at mitigating the environmental impacts of petroleum products have gained worldwide relevance. In this scenario, the production of bioplastics mainly from polysaccharides such as starch is a growing strategy and a field of intense research. The use of plasticizers, the preparation of blends, and the reinforcement of bioplastics with lignocellulosic components have shown promising and environmentally safe alternatives for overcoming the limitations of bioplastics, mainly due to the availability, biodegradability, and biocompatibility of such resources. This review addresses the production of bioplastics composed of polysaccharides from plant biomass and its advantages and disadvantages.

Steam explosion pretreatment improves acetic acid organosolv delignification of oil palm mesocarp fibers and sugarcane bagasse

Steam explosion can be used to pretreat lignocellulosic materials to decrease energy and chemical consumption during pulping to obtain environmentally friendly lignin and to improve lignin yield without changing its structure. The objective of this study was to evaluate the extraction of lignin from oil palm mesocarp fibers and sugarcane bagasse using steam explosion pretreatment followed by acetosolv. The biomasses were pretreated at 168 °C for a reaction time of 10 min. Steam explosion combined with acetosolv at lower severities was also carried out. Steam explosion followed by acetosolv increased the lignin yield by approximately 15% and 17% in oil palm mesocarp fibers and sugarcane bagasse, respectively. In addition, steam explosion decreased the reaction time of acetosolv four-fold while maintaining the lignin yield from sugarcane bagasse. Similar results were not obtained for oil palm mesocarp. High-purity and high-quality lignins were obtained using steam explosion pretreatment with structural characteristics similar to raw ones. Sugarcane bagasse lignin seems to be a better option for application in material science due its higher lignin yield and higher thermal stability. Our findings demonstrate that steam explosion is efficient for improving lignin yield and/or decreasing pulping severity.

Role of different lignin systems in polymers: mechanical properties and thermal stability

Lignin was used to study the mechanical properties and thermal stability of polymers. The lignin was blended with three kinds of polymers, and the addition of lignin was 0.5 wt%. Under the condition of thermal oxidation, the thermal stability of lignin/polymer samples varies with the structure of lignin. The effects of lignin on the mechanical properties and thermal stability of the polymers were investigated by oxidation induction time (OIT), rheological properties, mechanical properties and differential scanning calorimetry (DSC). The results show that the effect of lignin on the thermal properties of polymer samples is 2~3°C. It can be inferred that lignin can effectively improve the interaction between polymer molecular chain segments, and improve the crystallization rate and rigidity to a certain extent, so it can be seen that lignin has good compatibility and thermal stability.

Stepwise Ethanol-Water Fractionation of Enzymatic Hydrolysis Lignin to Improve Its Performance as a Cationic Dye Adsorbent

In this work, lignin fractionation is proposed as an effective approach to reduce the heterogeneity of lignin and improve the adsorption and recycle performances of lignin as a cationic dye adsorbent. By stepwise dissolution of enzymatic hydrolysis lignin in 95% and 80% ethanol solutions, three lignin subdivisions (95% ethanol-soluble subdivision, 80% ethanol-soluble subdivision, and 80% ethanol-insoluble subdivision) were obtained. The three lignin subdivisions were characterized by gel permeation chromatography (GPC), FTIR, 2D-NMR and scanning electron microscopy (SEM), and their adsorption capacities for methylene blue were compared. The results showed that the 80% ethanol-insoluble subdivision exhibited the highest adsorption capacity and its value (396.85 mg/g) was over 0.4 times higher than that of the unfractionated lignin (281.54 mg/g). The increased adsorption capacity was caused by the enhancement of both specific surface area and negative Zeta potential. The maximum monolayer adsorption capacity of 80% ethanol-insoluble subdivision by adsorption kinetics and isotherm studies was found to be 431.1 mg/g, which was much higher than most of reported lignin-based adsorbents. Moreover, the 80% ethanol-insoluble subdivision had much higher regeneration yield (over 90% after 5 recycles) compared with the other two subdivisions. Consequently, the proposed fractionation method is proved to be a novel and efficient non-chemical modification approach that significantly improves adsorption capacity and recyclability of lignin.

Enhanced enzymatic hydrolysis and methane production from rubber wood waste using steam explosion

Rubber wood waste (RW) requires due to its recalcitrance a pretreatment step before efficient biochemical conversion is possible. Non chemical steam explosion pretreatment was adopted to enhance enzymatic hydrolysis and anaerobic digestion with severity from 2.70 to 4.35. RW treated at severity 4.35 (214 °C for 10 min) gave the highest 83.9 L CH₄/kgVS effectiveness in anaerobic digestibility together with 45.2% hydrolysability in terms of glucan conversion. The intense pretreatment decreased particle size and degraded most of the hemicellulose, resulting in increased specific surface and better access for enzymes to cellulose. Additionally, the energy yield of steam exploded RW was enhanced by combined enzymatic hydrolysis with anaerobic digestion, in comparison to enzymatic hydrolysis or anaerobic digestion alone. This allowed for an efficient steam explosion pretreatment with co-production of sugar and methane. This study provides a technical approach for efficient biofuel production from RW after steam explosion pretreatment. Valorization of lignin-rich residue generated from the integrated process may increase value of RW, but assessing this requires further study.