Enzymatic hydrolysis at high lignocellulosic content: Optimization of the mixing system geometry and of a fed-batch strategy to increase glucose concentration

Working at high values of lignocellulosic Dry Matter (DM), as wheat straw, increases the reaction medium viscosity, making the mixing inefficient with the traditional agitators. Batch and fed-batch tests were conducted using different impellers: i) inclined blades, ii) marine impeller, iii) anchor, iv) paravisc and v) double helical impeller. Inclined blades appeared an inadequate device for batch and fed-batch tests. On contrary, double helical impellers and anchor gave optimal performances. An alternative to improve the reactor’s rheology is the modification of the feeding strategy. A particular fed-batch strategy allowed keeping low the reaction medium viscosity by a gradual increasing of the DM content in the reactor. In this way, three main benefits were achieved: i) a very good performances in terms of glucose concentration (85 g/L), ii) a strong reduction of the energetic consumption compared to batch test and iii) the adoption of a simple mixing devise. [Display omitted] •Enzymatic hydrolysis from wheat straw causes bad mixing at high DM content.•Different impellers have been tested in batch and fed-batch mode.•Small impellers were inefficacy, double helical impeller had high performances.•A fed-batch strategy (FBGA) has been implemented to use small impellers.•FBGA allowed to minimize energy consumption and to increase the glucose yield.