(519b) Hot-Water Pretreatment and Saccharification of Genetically Modified Cellulosic Feedstock for Fuel Production

Demand for transportation fuel, bioethanol and biodiesel, is ever increasing and they are significant contributor to a country’s economy. Increased research has been directed towards finding alternative renewable sources for the production of bioethanol and biodiesel. Understanding plant lipid biosynthesis and advances in genetic engineering tools has enabled researchers to develop modified crops capable of lipid production and accumulation. Lipids induced in vegetative tissue of energy crops are being projected as an alternative source of oil for biodiesel production. Beneficially, such crops are aimed to be cultivated on marginal land, thereby reducing stress on vegetable oil and avoiding the “food vs fuel” debate. Moreover, as cellulosic energy crops are used as a substrate for metabolic engineering to induce lipid, the cellulosic pretreatment approaches could be applicable for sugar and lipid recovery.

In this work, hot-water pretreatment to deconstruct the lipid containing cellulosic biomass to concentrate the lipid in residue and enable efficient enzymatic hydrolysis of polysaccharide backbone was evaluated. The biomass (bagasse) was composed of 35.32 ± 1.85% glucan, 20.62 ± 2.46% xylan and 17.01 ± 0.97% acid insoluble lignin. The biomass was pretreated at 170, 180, 190°C for different reaction times at 10% w/v solid loading. It was observed that under the optimal pretreatment condition, the cellulose content of the residue increased due to solubilization of hemicellulose and other components (Table 1). The residues and the autohydrolysate lipid content were quantified (Table 2) and analyzed for the triglyceride content (Figure 1). It can be noted that a concentration of triglycerides in the residue occurs upon pretreatment and the highest concentration was observed at 170°C. The pretreatment condition where highest lipid and cellulose content was observed in residue was selected for subsequent enzymatic hydrolysis. The pretreated residue was enzymatically hydrolyzed into constituent monosaccharides using a mixture of cellulases and hemicellulase. The residues and the liquor after enzymatic hydrolysis were analyzed for lipid content. The preliminary results are indicative of an increase in lipid content upon pretreatment and enzymatic hydrolysis. Moreover, high conversion of polysaccharides into constituent monosaccharides (glucose and xylose) was observed.

Thus, in this work, a cellulosic pretreatment approach was used to pretreat lipid-producing genetically engineered crop to obtain lipid and sugar. Thus, a single feedstock could potentially enable the production of two renewable fuels, biodiesel and bioethanol.