Enzymatic hydrolysis of pretreated Alfa fibers (Stipa tenacissima) using β-d-glucosidase and xylanase of Talaromyces thermophilus from solid-state fermentation

- Alfa fibers, an abundant holocellulose resource in Tunisia, are a promising substrate for the production of reducing sugars.
- β-d-glucosidases and xylanase of T. thermophilus AX4 obtained under solid state fermentation are used for Alfa fibers' hydrolysis.
- Alkali pretreatment with NaOH (1%) at 120 °C for 20 min of Alfa fibers improves 5-fold reducing sugars yield.
- The efficient saccharification yield of alkali pretreated Alfa fibers is 83%.

This work aims at realizing an optimal hydrolysis of pretreated Alfa fibers (Stipa tenacissima) through the use of enzymes produced from Talaromyces thermophilus AX4, namely β-d-glucosidase and xylanase, by a solid state fermentation process of an agro-industrial waste (wheat bran supplemented with lactose). The carbon source was firstly selected and the optimal values of three other parameters were determined: substrate loading (10 g), moisture content (85%) and production time (10 days); which led to an optimized enzymatic juice. The outcome was then supplemented with cellulases of T. reesei and used to optimize the enzymatic saccharification of alkali-pretreated Alfa fibers (PAF). The maximum saccharification yield of 83.23% was achieved under optimized conditions (substrate concentration 3.7% (w/v), time 144 h and enzyme loading of 0.8 FPU, 15 U CMCase, 60 U β-d-glucosidase and 125 U xylanase).The structural modification of PAF due to enzymatic saccharification was supported by the changes of morphologic and chemical composition observed through macroscopic representation, FTIR and X-Ray analysis.