In addressing the demand for sustainable alternatives to fossil fuel as a source of energy and consumer products, low cost, renewable lignocellulosic residues from municipal wastes, forest residues, food side-streams and energy crops have been the recent focus of intensive research. Elephant grass (EG; Pennisetum purpureum), also called Napier grass, is native to the tropical grasslands of Africa and has been introduced to most tropical and subtropical countries. Cultivation of EG can yield stems over 3 m in height, and can provide annual dry matter production levels of 88 metric tonnes per hectares per year. This grass has been used as animal fodder for many years, but the high growth potential and the solid center to the stems (pith), which is similar to maize and sugar cane, makes this grass a potential source of precursors of fine chemicals and bioenergy. During hydrolase treatment, he internal pith of EG is more extensively degraded (>50%) compared to the outer cortex (31%) or the whole EG stem (35%). The release of reducing sugars from the cortex was higher than from the pith. The presence of the pith may restrict enzyme accessibility to their substrates in solid stems compared to that published before for hollow stem biomass, such as wheat straw. The presence of dimethylsulfoxide (DMSO) reduced the solubility of EG, although enzymatic acetic acid release was increased, complimenting previous results found on model substrates. DMSO at low concentrations was also shown to have a protective effect on xylanase activity within Ultraflo when residual activity in the supernatant was measured in comparison to reactions performed in solely aqueous media. DMSO appears to be solubilising carbohydrate (xylan and glucan) in preference to lignin in the biomass but also leading to reduced solubility of other components in the EG.

Enzymatic degradation of elephant grass (<i>Pennisetum purpureum</i>) stems as a potential energy crop: Influence of the pith and bark in the total hydrolysis

247th National Meeting (2014)

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Enzymatic degradation of elephant grass (Pennisetum purpureum) stems as a potential energy crop: Influence of the pith and bark in the total hydrolysis