黑翅土白蚁菌圃共生菌对小麦秸秆的生物降解

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

摘要:

【目的】探究黑翅土白蚁(Odontotermes formosanus)菌圃共生菌在木质纤维素降解上的应用潜力，增加秸秆降解菌种资源并为秸秆资源产业化利用提供理论依据。【方法】以刚果红染色法、羧甲基纤维素钠平板分离筛选具有木质纤维素降解活性的黑翅土白蚁菌圃共生菌并测定共生菌产酶情况。在常温液态发酵条件下，评估不同菌种以及复合菌群对小麦(Triticum aestivum L.)秸秆的降解效果，利用傅里叶红外光谱、X射线晶体衍射和冷场扫描电镜分析降解前后小麦秸秆的理化性质。【结果】从黑翅土白蚁菌圃中分离得到具有木质纤维素降解活性的5种真菌和3种细菌，经鉴定为青霉属(Penicillium) 2种，紫霉属(Purpureocillium) 1种，曲霉属(Aspergillus) 1种，弯孢聚壳霉属(Eutypella) 1种，芽孢杆菌属(Bacillus) 1种，埃希氏菌属(Escherichia) 1种，寡养单胞菌属(Stenotrophomonas) 1种。经酶活测定和单菌降解试验筛选出4种高效降解菌株[桔青霉(Penicillium citrinum)、红绶曲霉(Aspergillus nomiae)、枯草芽孢杆菌(Bacillus subtilis)、大肠杆菌(Escherichia coli)]组成复合菌群。经常温液态发酵，4种菌组成的复合菌群的综合降解能力最强，在12 d内干物质降解率达到24.35%，纤维素降解率达到47.24%，半纤维素降解率达到35.75%，木质素降解率达到32.72%。降解后小麦秸秆内部化学键和分子间作用力受到破坏，木质纤维素复合结构受到破坏，纤维素结晶度从37.40%降低至32.97%，秸秆表面严重崩解，结构蓬松。【结论】从黑翅土白蚁菌圃中分离得到的桔青霉、红绶曲霉、枯草芽孢杆菌、大肠杆菌所组成的复合菌群对小麦秸秆有着优良的降解效果，具备秸秆生物降解产业化的潜在开发价值。

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.