Enzymatic hydrolysis of hemicellulose from pretreated Finger millet (Eleusine coracana) straw by recombinant endo-1,4-β-xylanase and exo-1,4-β-xylosidase

Abstract

This study focuses on enzymatic saccharification of hemicellulose part of the pretreated Finger millet straw (FMS) for production of xylose. The variation in the carbohydrate composition of FMS was analysed when subjected to different pretreatments. The recombinant endo-1,4-β-xylanase (CtXyn11A) was most active on the FMS pretreated with 1% (w/v) NaOH combined with oven heating at 120 °C for 20 min, resulting in a total reducing sugar yield (TRS) of 32 mg/g pretreated biomass. The pretreatment aided in concentrating the holocellulose content from 69.3% of raw powdered FMS to 76.4%. The post-treatment solid biomass yield was 0.36 g/g raw biomass. The two-step optimization of hemicellulose saccharification from the above pretreated FMS with i) endo-1,4-β-xylanase (CtXyn11A) at 55 °C and ii) exo-1,4-β-xylosidase (BoGH43A) at 37 °C, both at pH 7.5 by Box-Behnken design yielded the TRS of 70 mg/g pretreated biomass. The percentage conversion of xylan to xylose by CtXyn11A and BoGH43A was 24.7%.