# Lacase in Biorefinery of Lignocellulosic Biomass
## 2 Pretreatment of Lignocellulosic Biomasses  
Lignocellulosic biomasses are an abundant and renewable source of bioenergy, which have the potential to reduce dependence on non-renewable resources. However, the complex structure of lignocellulosic and its resistance to enzymatic hydrolysis present a major challenge to its utilization [12]. The removal or modification of lignin is necessary to increase the accessibility of the cellulose and hemicellulose fractions, which can be converted into biofuels, chemicals, and other valuable products. Pretreatment is a crucial step, regarded as one of the most cost-intensive steps in the process of lignocellulosic biomass conversion [13]. There are various techniques for biomass pretreatment which need to be selected wisely based on the nature of feedstock, process, end product, and its end application. Table 1 shows advantages and disadvantages of each pretreatment methods applied which is helpful to decide which one to use for particular biomass and process. Figure 1 shows a schematic of the effect of pretreatment on biomasses.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Pretreatment Technique** & **Principle** & **Advantages** & **Disadvantages** \\ \hline Biological Pretreatment & Most biological pretreatment methods utilize the ligninolytic enzyme system, which consists of oxidoreductase that can break down lignin, thereby enhancing biomass degradation. & Environmentally friendly and sustainable; can be conducted at low temperatures and pressures; generates fewer inhibitor compounds & Slow process; may require multiple stages; limited applicability to certain types of biomasses; high enzyme costs \\ \hline Hydrothermal Pretreatment & Water at subcritical temperature acts as a catalyst as it changes into the hydronium ion, the pH becomes acidic and liquifies the cellulose and hemicellulose to an extent. & Environmentally friendly and sustainable; can be conducted without chemicals or solvents; can improve the accessibility of cellulose; can produce high sugar and ethanol yields & Requires a significant energy input; may generate significant amounts of inhibitor compounds; limited effect on lignin \\ \hline Organosolv Pretreatment & Dissolves lignin and hemicellulose, leaving behind solid crystalline cellulose. & Can selectively extract lignin and hemicellulose; yields high-quality lignin that can be used for high-value products; can be conducted at low temperatures and pressures; generates fewer inhibitor compounds than acid pretreatments & Requires the use of organic solvents, which can be expensive and hazardous; may generate significant amounts of waste; can be energy-intensive; limited scalability \\ \hline  & & More environmentally friendly than concentrated acid pretreatments; can selectively remove hemicellulose and increase the accessibility of cellulose; can produce high sugar and ethanol yields & Generates significant amounts of inhibitor compounds; requires a large amount of water and energy input; limited applicability to cerium types of biomasses; may require multiple stages \\ \hline  & & Alkali pretreatment changes the lignocellulosic structure by causing cellulose swelling, reducing crystallinity, and increasing polymerization. The internal surface area is enhanced due to the removal of acetyl groups anduronic acids from hemicellulose. & Can be effective at breaking down lignin and hemicellulose; can increase accessibility to cellulose; can produce high sugar and ethanol yields & May require significant amounts of water \\ \hline \hline \end{tabular}
\end{table}
Table 1: Table showing different pretreatment techniques and their advantages and disadvantages.  
Figure 1: Effect of pretreatment on biomasses.