Recent studies on high solids hydrolysis and fermentation of lignocellulosic material to ethanol often focus on solids concentrations above 10%.
Using this strategy gave a higher glucan conversion at a lower enzyme dose than in many other high solids hydrolysis studies [ 51- 53].
From an industrial point of view it is interesting to note that operating the high solids hydrolysis of lignocellulosic material following an SHF (50°C) configuration leads to less gluconic acid produced (2.8% of glucose released) compared to the SSF (33°C) giving 4.1% of glucose released.
Higher solids hydrolysis is required to achieve a high sugar titer.
Working with initial reaction velocities in high-solids hydrolysis involves great difficulties due to the non-liquid properties of the substrate.
High solid loading hydrolysis was based on 6% glucan (cellulose + starch) loading for each substrate.
For example, in their studies on high solid enzymatic hydrolysis in rotating drums, Roche et al.[ 15] and Jorgensen et al.[ 16] argue that once the enzymes are evenly distributed, the influence of mixing is negligible.
In this work, we monitor the impeller torque (and hence power input) in a stirred tank reactor throughout high solid enzymatic hydrolysis (< 20% WIS) of steam-pretreated Arundo donax and spruce.
For an industrial high solid loading hydrolysis, more βG and βX might be necessary in order to overcome the build-up of sugar oligomers due to the inhibition of enzymes at high concentrations of monosaccharides and potential unproductive binding to lignin.
However, this factor should not significantly impact the final conclusions of this paper and is a previously acknowledged limitation in peer-reviewed literature [ 21].Throughout the course of high solid loading hydrolysis of the pretreated substrates, liquid samples were taken every 24 hours to estimate monomeric sugar concentrations.
