The Effect of <i>Gleditsia</i> Saponin on Simultaneous Saccharification and Fermentation of Furfural Residue for Ethanol Production

A Review on the Transformation of Furfural Residue for Value-Added Products

As a by-product of lignocellulosic depolymerization for furfural production, furfural residue (FR) is composed of residual cellulose, lignin, humic acid, and other small amounts of materials, which have high reuse value. However, due to the limitation of furfural production scale and production technology, the treatment of FR has many problems such as high yield, concentrated stacking, strong acidity, and difficult degradation. This leads to the limited treatment methods and high treatment cost of furfural residue. At present, most of the furfural enterprises can only be piled up at will, buried in soil, or directly burned. The air, soil, and rivers are polluted and the ecological balance is destroyed. Therefore, how to deal with furfural residue reasonably needs to be solved. In this review, value-added products for furfural residue conversion are described in detail in the fields of soil culture, catalytic hydrolysis, thermal decomposition, and porous adsorption. The future studies reporting the FR to convert value-added products could find guidance from this review to achieve specific goals.

Comparative study of simultaneous saccharification and fermentation byproducts from sugarcane bagasse using steam explosion, alkaline hydrogen peroxide and organosolv pretreatments

Most of the hemicelluloses were removed and more acetyl groups were generated after steam pretreatment, and a high acetic acid concentration was observed during SSF.

Enhancement of fermentable sugar yield by competitive adsorption of non-enzymatic substances from yeast and cellulase on lignin

BACKGROUND

Enhancement of enzymatic digestibility by some supplementations could reduce enzyme loading and cost, which is still too high to realize economical production of lignocellulosic biofuels. A recent study indicates that yeast hydrolysates (YH) have improved the efficiency of cellulases on digestibility of furfural residues (FR). In the current work, the components of YH were separated by centrifugation and size exclusion chromatography and finally characterized in order to better understand this positive effect.

RESULTS

A 60.8% of nitrogen of yeast cells was remained in the slurry (YHS) after hydrothermal treatment. In the supernatant of YH (YHL), substances of high molecular weight were identified as proteins and other UV-absorbing compounds, which showed close molecular weight to components of cellulases. Those substances attributed to a synergetic positive effect on enzymatic hydrolysis of FR. The fraction of YHL ranged from 1.19 to 2.19 mL (elution volume) contained over 50% of proteins in YHL and had the best performance in stimulating the release of glucose. Experiment results proved the adsorption of proteins in YHL on lignin.

CONCLUSIONS

Supplementation of cellulases with YH enhances enzymatic digestibility of FR mainly by a competitive adsorption of non-enzymatic substances on lignin. The molecular weight of these substances has a significant impact on their performance. Different strategies can be used for a good utilization of yeast cells in terms of biorefinery concept.

Evaluation of cellulases produced from four fungi cultured on furfural residues and microcrystalline cellulose

Four fungal strains-Trichoderma viride, Aspergillus niger, Trichoderma koningii, and Trichoderma reesei-were selected for cellulase production using furfural residues and microcrystalline cellulose (MCC) as the substrates. The filter paper activity (FPA) of the supernatant from each fungus was measured, and the performance of the enzymes from different fungal strains was compared. Moreover, the individual activities of the three components of the cellulase system, i.e., β-glucosidase, endoglucanase, and exoglucanase were evaluated. T. koningii showed the highest activity (27.81 FPU/ml) on furfural residues, while T. viride showed an activity of 21.61 FPU/ml on MCC. The FPA of the crude enzyme supernatant from T. koningii was 30% higher on furfural residues than on MCC. T. koningii and T. viride exhibited high stability and productivity and were chosen for cellulases production. The crystallinity index (CrI) of the furfural residues varied after digested by the fungi. The results indicated differences in the functioning of the cellulase system from each fungus. In the case of T. koningii, T. reesei and T. viride, furfural residues supported a better environment for cellulase production than MCC. Moreover, the CrI of the furfural residues decreased, indicating that this material was largely digested by the fungi. Thus, our results suggest that it may be possible to use the cellulases produced from these fungi for the simultaneous saccharification and fermentation of lignocellulosic materials in ethanol production.