Combination of alkaline and enzymatic pre-treatment to increase bio-methane production potential of sorghum and wheat straw.

the purpose of this study was to increase methane production by enzymatic and combined alkalineenzymatic pre-treatments on ensiled sorghum forage and wheat straw. Sodium hydroxide pre-treatment was conducted by soaking samples in a NaOH solution. Enzymatic pre-treatment was comparatively performed employing four commercial preparations. Enzyme preparations were first characterized for their protein, CMCase (endoglucanase), xylanase and avicelase activities, and then added to untreated or alkaline pre-treated substrates. To assess the effect of the applied pre-treatment on the methane production, Biochemical Methane Potential (BMP) tests, before and after the enzymatic and the combined alkaline-enzymatic pre-treatment, were performed. Glucose was the prevailing monosaccharide released by enzymatic treatments, but xylose, mannose and galactose, as well as arabinose and glucuronic acid were also found. Combined alkaline-enzymatic pre-treatment resulted in the highest methane yield increase (+32% and +76% for ensiled sorghum and wheat straw respectively).