Extraction and characterization of Eucommia ulmoides gum from Eucommia leaves by fermentation with Coprinellus disseminatus.

AIMS

To determine the optimum conditions for extracting Eucommia ulmoides gum (EUG) from E. ulmoides leaves during fermentation by Coprinellus disseminatus. At the same time, the EUG characteristics were characterized.

METHODS AND RESULTS

The ability of C. disseminatus to secrete degrading enzymes, including enzyme activity and lignocellulose content, was observed by culturing C. disseminatus on a medium with different formulations. Based on the optimal formula, the fermentation conditions were determined by an orthogonal test and EUG was extracted. After that, the characteristic parameters of EUG were determined by Fourier transform infrared (FT-IR), 1hydrogen-nuclear magnetic resonance (1H-NMR), scanning electron microscopy (SEM), polarizing optical microscope (POM), differential scanning calorimeter (DSC), X-ray diffractometer (XRD), and gel permeation chromatography (GPC). The results showed that the lignin and hemicellulose contents in Eucommia leaves decreased significantly with the increase of fermentation days, and C. disseminatus mediated fermentation had an obvious damage effect on the tissue of Eucommia leaves. At the same time, xylan can be used as an initiator to induce the expression of degradation-related enzymes. The extraction yield of EUG from E. ulmoides leaves after fermentation was 3.06%, which was significantly improved. The optimum fermentation conditions were 4% inoculum, 28°C fermentation temperature, and pH = 5. The results of infrared FT-IR and 1H-NMR showed that the extract had typical characteristics of EUG, and the surface and quenching part of the EUG were smooth, as observed by SEM. In addition, DSC and XRD analysis show that there are two crystal types, α and β, in the crystallization process of molten EUG. The main crystallization type of EUG extracted from fermented leaves was β type.

CONCLUSION

The ability of C. disseminatus to produce degrading enzymes can effectively improve the extraction rate of EUG under optimal fermentation process. The method can maintain the integrity of gutta-percha better. EUG has the characteristics of good crystallinity, many β crystal types and high molecular weight.