Pretreatment Synthesis

1360 Words6 Pages
As discussed in section 4.0, the biochemical conversion of lignocellulosic feedstocks to fuels and chemicals via soluble sugar intermediates requires a pretreatment step prior to the biological steps of enzymatic saccharification and fermentation (Mosier et al. 2005a). This pretreatment process helps to overcome the natural resistance of lignocellulosic feedstocks to biological degradation and reduces the recalcitrance of cellulose and hemicellulose to better enable conversion of these structural carbohydrates to soluble sugars (Elander et al., 2009). The pretreatment step is the most expensive capital investment in the biochemical conversion route of lignocellulosic feedstocks to ethanol (Wooley et al. 1999) and has been found to substantially…show more content…
2005a). The increase of sugar yields by proper selection and optimization of the pretreatment operation can also impact the effectiveness and cost of the other process conversion steps. Pretreatment is found to directly affect the amount and types of enzymes required to further saccharify all plant cell wall structural carbohydrates to monomeric sugars, as some pretreatment approaches are able to hydrolyze virtually all of the hemicellulose directly to monomeric xylose while other pretreatment approaches largely leave the hemicellulose intact, or only achieve partial hydrolysis to oligomeric sugars (Mosier et al. 2005a). The type and severity of the pretreatment process can also affect the amount, type and concentration of potential inhibitory compounds that can be released in soluble form directly from the biomass itself (such as acetic acid from acetylated hemicellulose or phenolics or other organic compounds released from lignin) or those produced as products from sugar degradation reactions (such as aldehydes and organic acids most commonly associated with dilute acid pretreatment). These inhibitory products can affect the fermentation…show more content…
Lignocellulosic biomass, including agricultural and forestry residues instead of traditional feedstocks (starch crops), could prove to be an ideally inexpensive and abundantly available source of sugar for fermentation into transportation fuels. Cellulose crystallinity, accessible surface area, protection by lignin, and sheathing by hemicellulose all contribute to the resistance of cellulose in biomass to hydrolysis. The biomass pretreatment and the intrinsic structure of the biomass itself are basically responsible for its subsequent hydrolysis. The conditions used in the chosen pretreatment method will affect various substrate characteristics. This in turn, govern the susceptibility of the substrate to hydrolysis and the subsequent fermentation of the released sugars. Therefore, pretreatment of biomass is a very important step in the synthesis of biofuels from lignocellulosic feedstocks. There is a critical requirement to understand the fundamentals of various processes, which can help in making a suitable choice depending on the structure of the biomass substrate and the hydrolysis

More about Pretreatment Synthesis

Open Document