Unlike the bioconversion of cellulose into fuels or chemicals, hemicellulose conversion with desired yields and productivities is still a challenge, as hemicellulosic hydrolyzate is composed mainly of 5-carbon sugars (xylose, arabinose) and some undesired compounds which are released from the hemicellulose structure.
Conditions for maximum hemicellulose solubilisation (2% H2SO4 for 60 min at 121 °C) differed to those associated with maximum glucose release from solid residue saccharifications (1% H2SO4/90 min /121 °C).
The optimum conditions to get maximum hemicellulose extraction and solids recovery were found to be 13%% substrate concentration and 90 min of isothermal treatment [14].
Additionally, a hemicellulose conversion can be considered along with a cellulose conversion to quantify the effectiveness of biomass enzymatic hydrolysis.
The heat is a very important condition for hemicellulose conversion to sugars [ 2].
It will also be interesting to simultaneously express both cellulose and hemicellulose degrading enzymes to increase the efficiency of cellulose and hemicellulose conversion into glucose and xylose, respectively.
Therefore, the fractionation of hemicellulose from WS by SE and the building of hemicellulose sugar platform should improve the hemicellulose conversion performance for bio-based products such as xylitol, furfural, and ethanol.
The maximum hemicellulose fractionation yield was 73% in SE, while the maximum lignin fractionation yield was 90% in ethanol extraction.
Furthermore, the poor enzymatic hemicellulose conversion observed in this study calls for a detailed study of the hemicellulose structure in pretreated grass and identification of structures which could be responsible for the inefficient enzymatic conversion.
Hence, an effective pretreatment must achieve good hemicellulose conversion yields and produce an easily digestible cellulosic solid.
