Ultrastructural changes associated with different pretreatments on napier grass

Abstract

In response to concerns over growing energy demands and depleting resources, renewable fuels derived from second generation lignocellulosic biomass have the potential to replace non-renewable, fossil fuels. Optimizing the process of converting biomass to monomeric sugars, the precursor of most biofuels, is limited by two primary factors: (1) the inefficiency of enzymes that hydrolyze cellulose into monomeric sugars; and (2) the recalcitrant structures (and limited exposure of cellulose to cellulolytic enzymes). The aim of this study was to investigate the ultrastructure of the biomass and the morphological changes that occur after pretreatment. Napier grass (Pennisetum purpureum) was investigated under the following pretreatment strategies: dilute acid hydrolysis, sonication and the combination of both acid and sonication, and was visualized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). A structurally supportive sclerenchyma cell naturally has a higher lignin (an enzyme inhibitor) content than a parenchyma cell. Results revealed increased lignin deposition on sclerenchyma cells than on parenchyma cells by a range of 10-20%. Lignin deposition greater than 40% at the bottom of the cell indicated unfavorably low sugar yields.