Enhanced saccharification of steam explosion pretreated corn stover by the supplementation of thermoacidophilic β-glucosidase from a newly isolated strain, Tolypocladium cylindrosporum syzx4

Abstract

Newly isolated fungi, strain Tolypocladium cylindrosporum syzx4 from rotten corn stover, can effectively produced extracellular thermoacidophilic β-glucosidase (syzx4) using agro-industrial residues. After purification and characterization, the β-glucosidase was applied to saccharify steam explosion pretreated corn stover (SCS) with commercial celluclast from Trichoderma reesei when compared with the β-glucosidase (Novo-188) fromAspergillus niger supplementation. Based on the results of the single factor tests, further studied with the response surface methodology (RSM), amid a five level four-factor central composite design (CCD), was designed for the optimal hydrolysis parameters, such as the substrate concentration, pH, temperature and the ratio of celluclast to syzx4, in order to achieve the highest saccharification yield. The substrate concentration and the ratio of celluclast to syzx4 were identified as the limiting factor for the saccharification yield. A maximum saccharification yield of 88.4% was obtained at an optimal hydrolysis condition as follows: substrate concentration (3.05%), pH (3.73), temperature (43.4°C) and the ratio of syzx4 to celluclast [0.91 (18.2 BGU/g substrate): 1 (20 FPU/g substrate)]. The results of a confirmation experiment under the optimum conditions were in agreement with model predictions and they obtained the maximum value of 88.4% saccharification yield. The results suggested that the β-glucosidase (syzx4) from T. cylindrosporum is a good supplementation for the production of reducing sugars from cellulosic biomass. Key words: Saccharification, steam explosion pretreated corn stover (SCS), β-glucosidase, Tolypocladium cylindrosporum syzx4, hydrolysis parameters, response surface methodology (RSM).