一株地衣芽孢杆菌对稻草降解作用的研究

Study on degradation of rice straw by Bacillus licheniformis

通过测定发酵过程中发酵液的纤维素酶活、半纤维素酶活、可溶性总糖和还原糖浓度以及底物残渣重、残渣结晶度、傅立叶红外光谱和表面结构的变化来研究地衣芽孢杆菌(Bacillus licheniformis)对稻草的降解作用.研究发现,在发酵过程中地衣芽孢杆菌菌体产酶过程也就是木质纤维素的降解糖化过程.上清液中的纤维素酶活和半纤维素酶活分别在发酵进行到第12 h和48 h时达到最高峰.总糖含量于第4 h达到最高值,然后下降到一定程度后保持恒定.还原糖含量随发酵进行不断下降,达到一定值后保持恒定.该菌株对稻草长达5 d的降解过程中结晶度未发生明显变化.底物残渣傅立叶红外光谱分析表明,此菌株对稻草中各组分都有一定降解.稻草中纤维素、半纤维素和木质素的降解率分别为14.91%、6.61%和1.42%.利用扫描电镜对底物残渣表面结构进行观察,可看到该菌株主要降解稻草的薄壁细胞,使其发生严重皱缩.

The degradation of rice straw by Bacillus licheniformis was studied, by measuring activities of cellulase and hemi-cellulase, concentration of reducing sugar and soluble total sugar in fermented broth, weight loss, crystallinity, FT-IR and surface structure of residue. The results showed that the process of biodegradation of lignocellulose is actually simultaneous saccharification and fermentation. Cellulase and hemi-cellulase activities reached highest level in 12 h and 48 h, respectively. Concentration of soluble total sugar reached highest level in 4 h, and then decreased with time and maintained invariable level, Meanwhile concentration of reducing sugar decreased with fermentation and then maintained invariable level. Crystallinity of residue had not obvious change after 5 d cultivation. FT-IR spectrum of residue showed that B. licheniformis degraded cellulose, hemi-cellulose and lignin in rice straw in some extent,After 5 d cultivation, the degradation ratio of cellulose, hemi-cellulose and lignin in rice straw were 14.91%, 6.61% and 1.42%, respectively. Scanning electron microscope observation of surface structure of degraded rice straw by B. licheniformis showed that thin-walled cell of rice straw became wrinkled and wizen.