Mixing Effects on Enzymatic Hydrolysis of Steam-exploded Spruce

Scientists from the Department of Chemical Engineering, Lund University (Sweden) mention that mixing is an important consideration in the scale up of the enzymatic hydrolysis step in the conversion of lignocellulosic biomass for ethanol production. Enzymatic hydrolysis is the conversion of carbohydrate polymers in the pretreated lignocellulosic biomass (mainly cellulose and hemicelluloses) into (ethanol-fermentable) sugars by the use of enzymes. Pretreated biomass with a high water-insoluble-solids (WIS) content is preferred during enzymatic hydrolysis, because it usually results in higher ethanol yields after fermentation. However, a high WIS increases viscosity of the reaction system during enzymatic hydrolysis and can increase mixing power requirements. This would result in a higher energy cost .

The University of Lund scientists investigated the relationship between mixing intensity and enzymatic hydrolysis performance of steam-exploded spruce in stirred tank reactors. Spruce trees are coniferous trees belonging to the genus Picea, and have been traditionally cultivated for paper and construction uses. These trees have also been considered as a potential biofuel feedstocks. The researchers confirmed the strong effect of mixing enzymatic hydrolysis, and interplays with both enzyme loading and hydrolysis residence time. This interplay can be harnessed to obtain a high degree of reaction performance.

The full-results of the study are published in the open access journal, Biotechnology for Biofuels (URL above).