Biodegradation of wheat straw by symbiotic fungi and bacteria of Odontotermes formosanus

Abstract:

[Objective] This study explored the application potential of symbiotic fungi and bacteria of Odontotermes formosanus in the degradation of wheat (Triticum aestivum L.) straw resources, aiming to provide a theoretical basis and supplement strain resources for the industrialization of straw biodegradation. [Methods] The lignocellulose-degrading fungi and bacteria were isolated from O. formosanus and screened by Congo red staining and the agar plate supplemented with carboxymethyl cellulose sodium (CMC-Na), and the enzyme production of the strains screened out was examined. Liquid fermentation at room temperature was carried out to evaluate the degradation effects of different strains and strain combinations on wheat straw. Fourier transform infrared spectroscopy (FTIR), X-ray crystal diffraction (XRD), and scanning electron microscopy (SEM) were employed to analyze the physical and chemical properties of wheat straw before and after degradation. [Results] Five species of fungi and three species of bacteria were isolated from the termite combs, including two species of Penicillium, one species of Purpureocillium, one species of Aspergillus, one species of Eutypella, one species of Bacillus, one species of Escherichia, and one species of Stenotrophomonas. Four efficient degrading strains were screened out and identified as Penicillium citrinum, Aspergillus nomiae, Bacillus subtilis, and Escherichia coli. In the liquid fermentation at room temperature, the combination of the four strains had the strongest comprehensive degradation performance, with the degradation rates of 24.35%, 47.24%, 35.75%, and 32.72% for dry matter, cellulose, hemicellulose, and lignin, respectively, in 12 days. The degradation destroyed the chemical bonds, the intermolecular force, and the composite structure of lignocellulose in wheat straw, and decreased the crystallinity of cellulose from 37.40% to 32.97%. [Conclusion] The combination of P. citrinum, A. nomiae, B. subtilis, and E. coli isolated from the combs of O. formosanus had a good degradation effect on wheat straw, demonstrating the application potential in the industrialization of straw biodegradation.