Lignocellulosic BiomassLignocellulosic biomass is defined as a plant, or plant-derived, material that is mostly composed of cellulose, hemicellulose, and lignin. Lignocellulosic feedstocks are highly abundant, covering many biomass types including grasses, wood, energy crops (e.g. Miscanthus and coppices), agricultural residues (e.g. straws and corn stover), and municipal wastes.
Need for PretreatmentFor this reason, most hydrolysis technologies employ pre-treatment processes that aim to break apart the matrix (and in particular the associations between lignin and cellulose), reduce cellulose crystallinty, and hydrolyse hemicelluloses, hence separating the hydrolysate from cellulose which can then undergo more severe/targeted treatment.
Ionic-Liquid Biomass PretreatmentIonic liquids are salts in which the ions are poorly coordinated, resulting in these solvents being liquid below 100oC, or even at room temperature. They have gained a lot of interest in recent years for the pretreatment of lignocellulosic biomass due to their unique properties. For example, ionic liquids can possess excellent thermal stability, negligible vapor pressure, and high solvation power, making them ideal candidates for biomass pretreatment.
Hydrogen-Peroxide Pretreatment of BiomassHydrogen peroxide (H2O2) pretreatment primarily targets the lignin in the biomass. This works by oxidizing the phenolic structures of lignin, breaking it down into smaller fragments and increasing the accessibility of cellulose and hemicellulose to enzymatic hydrolysis.
Ultrasonic Biomass PretreatmentUltrasonic pretreatment is a physical method used to improve the conversion of lignocellulosic biomass into fermentable sugars. Ultrasonication involves the use of high-frequency sound waves to disrupt the structure of the biomass, making the cellulose more accessible to enzymatic hydrolysis.
Microwave-Assisted Biomass PretreatmentMicrowave-assisted pretreatment is a physical method used to enhance the conversion of lignocellulosic biomass. It uses the electromagnetic energy generated by microwaves to heat the biomass, often in combination with chemical reagents, such as acids, alkalis, or ionic liquids.
Fungal Biomass PretreatmentIn fungal pretreatment the primary goal is to break down lignin. The two main types of fungi used in fungal pretreatment are white-rot and brown-rot fungi, descrbed below.
Bacterial Biomass PretreatmentBacterial pretreatment of lignocellulosic biomass involves the use of certain bacteria that produce cellulases, hemicellulases, and ligninases, enzymes that can degrade cellulose, hemicellulose, and lignin respectively. This approach aims to increase the accessibility and digestibility of biomass for subsequent bioconversion processes. Different bacterial species have been studied for this purpose: