Liquid Hot Water Pretreatment of Lignocellulosic Biomass at Lab and Pilot Scale

Riboflavin overproduction on lignocellulose hydrolysate by the engineered yeast Candida famata

Lignocellulose (dry plant biomass) is an abundant cheap inedible residue of agriculture and wood industry with great potential as a feedstock for biotechnological processes. Lignocellulosic substrates can serve as valuable resources in fermentation processes, allowing the production of a wide array of chemicals, fuels, and food additives. The main obstacle for cost-effective conversion of lignocellulosic hydrolysates to target products is poor metabolism of the major pentoses, xylose and L-arabinose, which are the second and third most abundant sugars of lignocellulose after glucose. We study the oversynthesis of riboflavin in the flavinogenic yeast Candida famata and found that all major lignocellulosic sugars, including xylose and L-arabinose, support robust growth and riboflavin synthesis in the available strains of C. famata. To further increase riboflavin production from xylose and lignocellulose hydrolysate, genes XYL1 and XYL2 coding for xylose reductase and xylitol dehydrogenase were overexpressed. The resulting strains exhibited increased riboflavin production in both shake flasks and bioreactors using diluted hydrolysate, reaching 1.5 g L-1.

Revolutionizing lignocellulosic biomass: A review of harnessing the power of ionic liquids for sustainable utilization and extraction

The potential for the transformation of lignocellulosic biomass into valuable commodities is rapidly growing through an environmentally sustainable approach to harness its abundance, cost-effectiveness, biodegradability, and environmentally friendly nature. Ionic liquids (ILs) have received considerable and widespread attention as a promising solution for efficiently dissolving lignocellulosic biomass. The fact that ILs can act as solvents and reagents contributes to their widespread recognition. In particular, ILs are desirable because they are inert, non-toxic, non-flammable, miscible in water, recyclable, thermally and chemically stable, and have low melting points and outstanding ionic conductivity. With these characteristics, ILs can serve as a reliable replacement for traditional biomass conversion methods in various applications. Thus, this comprehensive analysis explores the conversion of lignocellulosic biomass using ILs, focusing on main components such as cellulose, hemicellulose, and lignin. In addition, the effect of multiple parameters on the separation of lignocellulosic biomass using ILs is discussed to emphasize their potential to produce high-value products from this abundant and renewable resource. This work contributes to the advancement of green technologies, offering a promising avenue for the future of biomass conversion and sustainable resource management.

Polymeric Materials Obtained by Extrusion and Injection Molding from Lignocellulosic Agroindustrial Biomass

This review presents the advances in polymeric materials achieved by extrusion and injection molding from lignocellulosic agroindustrial biomass. Biomass, which is derived from agricultural and industrial waste, is a renewable and abundant feedstock that contains mainly cellulose, hemicellulose, and lignin. To improve the properties and functions of polymeric materials, cellulose is subjected to a variety of modifications. The most common modifications are surface modification, grafting, chemical procedures, and molecule chemical grafting. Injection molding and extrusion technologies are crucial in shaping and manufacturing polymer composites, with precise control over the process and material selection. Furthermore, injection molding involves four phases: plasticization, injection, cooling, and ejection, with a focus on energy efficiency. Fundamental aspects of an injection molding machine, such as the motor, hopper, heating units, nozzle, and clamping unit, are discussed. Extrusion technology, commonly used as a preliminary step to injection molding, presents challenges regarding fiber reinforcement and stress accumulation, while lignin-based polymeric materials are challenging due to their hydrophobicity. The diverse applications of these biodegradable materials include automotive industries, construction, food packaging, and various consumer goods. Polymeric materials are positioned to offer even bigger contributions to sustainable and eco-friendly solutions in the future, as research and development continues.

Bioethanol production from agricultural residues as lignocellulosic biomass feedstock's waste valorization approach: A comprehensive review

Bioenergy is becoming very popular, drawing attention as a renewable energy source that may assist in managing growing energy costs, besides possibly affording revenue to underprivileged farmers and rural populations worldwide. Bioethanol made from agricultural residual-biomass provides irreplaceable environmental, socioeconomic, and strategic benefits and can be considered as a safe and cleaner liquid fuel alternative to traditional fossil fuels. There is a significant advancement made at the bench scale towards fuel ethanol production from agricultural lignocellulosic materials (ALCM). These process technologies include pretreatment of ALCM biomass employment of cellulolytic enzymes for depolymerizing carbohydrate polymers into fermentable sugars to effectively achieve it by applying healthy fermentative microbes for bioethanol generation. Amongst all the available process methods, weak acid hydrolysis followed by enzymatic hydrolysis process technique. Recovering higher proficient celluloses is more attractive in terms of economic benefits and long-term environmental effects. Besides, the state of ALCM biomass based bioethanol production methods is discussed in detail, which could make it easier for the scientific and industrial communities to utilize agricultural leftovers properly.

Recent updates to microbial production and recovery of polyhydroxyalkanoates

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum.

Advances in process design, techno-economic assessment and environmental aspects for hydrothermal pretreatment in the fractionation of biomass under biorefinery concept

The development and sustainability of second-generation biorefineries are essential for the production of high added value compounds and biofuels and their application at the industrial level. Pretreatment is one of the most critical stages in biomass processing. In this specific case, hydrothermal pretreatments (liquid hot water [LHW] and steam explosion [SE]) are considered the most promising process for the fractionation, hydrolysis and structural modifications of biomass. This review focuses on architecture of the plant cell wall and composition, fundamentals of hydrothermal pretreatment, process design integration, the techno-economic parameters of the solubilization of lignocellulosic biomass (LCB) focused on the operational costs for large-scale process implementation and the global manufacturing cost. In addition, profitability indicators are evaluated between the value-added products generated during hydrothermal pretreatment, advocating a biorefinery implementation in a circular economy framework. In addition, this review includes an analysis of environmental aspects of sustainability involved in hydrothermal pretreatments.

Liquid hot water pretreatment combined with high-solids enzymatic hydrolysis and fed-batch fermentation for succinic acid sustainable processed from sugarcane bagasse

In order to sustainable process of bio-succinic acid (SA), response surface methodology (RSM) was applied to optimize liquid hot water pretreatment pretreatment of sugarcane bagasse (SCB), followed by high-solids enzymatic hydrolysis of pretreated residual that without washing, then the hydrolysates and partial pretreatment liquid were used as carbon sources for SA fermentation. Results showed that the highest sugars yield could be achieved at pretreatment conditions of temperature 186 °C, time 25 min and solid-to-liquid ratio 0.08; enzymatic digestion the pretreated residuals at 20 % (w/v) solid content via enzymes reconstruction and fed-batch strategy, the obtained sugars reached to 121 g/L; by controlling the nutrition and conditions of the fermentation process, most of the C5 and C6 sugars in the hydrolysate and pretreatment liquid were converted into SA with a conversion rate high to 280 mg/g SCB. This study can provide a novel clue for clean and efficient biorefining of chemicals.

Two-Stage Pretreatment of Jerusalem Artichoke Stalks with Wastewater Recycling and Lignin Recovery for the Biorefinery of Lignocellulosic Biomass

Jerusalem artichoke (Helianthus tuberosus L.) is emerging as one of the energy plants considered for biofuel production. Alkali and alkali-involved pretreatment methods have been widely used for the bioconversion of cellulosic materials due to their high sugar yield and low inhibitor release. However, the recovery and treatment of wastewater (black liquor) have been poorly studied. Here, we present a novel two-stage pretreatment process design for recycling black liquor. Jerusalem artichoke stalk (JAS) was first treated with 2% (w/v) NaOH, after which lignin was recovered by H2SO4 at pH 2.0 from the black liquor. The recycled solutions were subsequently used to treat the NaOH-pretreated JAS for the second time to dissolve hemicellulose. CO-pretreated JAS, hydrolysates, and acid-insoluble lignin were obtained after the above-mentioned two-stage pretreatment. A reducing sugar yield of 809.98 mg/g Co-pretreated JAS was achieved after 48 h at 5% substrate concentration using a cellulase dosage of 25 FPU/g substrate. In addition, hydrolysates containing xylose and acid-insoluble lignin were obtained as byproducts. The pretreatment strategy described here using alkali and acid combined with wastewater recycling provides an alternative approach for cellulosic biorefinery.

Recent Advancements and Challenges in Lignin Valorization: Green Routes towards Sustainable Bioproducts

The aromatic hetero-polymer lignin is industrially processed in the paper/pulp and lignocellulose biorefinery, acting as a major energy source. It has been proven to be a natural resource for useful bioproducts; however, its depolymerization and conversion into high-value-added chemicals is the major challenge due to the complicated structure and heterogeneity. Conversely, the various pre-treatments techniques and valorization strategies offers a potential solution for developing a biomass-based biorefinery. Thus, the current review focus on the new isolation techniques for lignin, various pre-treatment approaches and biocatalytic methods for the synthesis of sustainable value-added products. Meanwhile, the challenges and prospective for the green synthesis of various biomolecules via utilizing the complicated hetero-polymer lignin are also discussed.

A Cleaner Delignification of Urban Leaf Waste Biomass for Bioethanol Production, Optimised by Experimental Design

This work is focused on optimising a low-temperature delignification as holocellulose purification pretreatment of Platanus acerifolia leaf waste for second-bioethanol production. Delignification was accomplished by acid-oxidative digestion using green reagents: acetic acid and 30% hydrogen peroxide 1:1. The effect of reaction time (30–90 min), temperature (60–90 °C), and solid loading (5–15 g solid/20 g liquid) on delignification and solid fraction yield were studied. The process parameters were optimised using the Box–Behnken experimental design. The highest attained lignin removal efficiency was larger than 80%. The optimised conditions of delignification, while maximising holocellulose yield, pointed to using the minimum temperature of the examined range. Analysis of variance on the solid fraction yield and the lignin removal suggested a linear model with a negative influence of the temperature on the yield. Furthermore, a negative effect of the solid loading and low effect of temperature and time was found on the degree of delignification. Then the temperature range was extended back to 60 °C, providing 71% holocellulose yield and 70% while improving energy efficiency by working at a lower temperature. Successful lignin removal was confirmed using confocal laser scanning microscopy. As evaluated by scanning electron microscopy, the solid structure presented an increased exposition of the cellulose fibre structure.