地衣芽孢杆菌对麦麸降解作用的研究

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质量、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 sp. X18)对麦麸的降解作用.发现在发酵过程中此菌体产酶的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96和 48 h 时达到最高峰.发酵液中总糖和还原糖含量分别于4和 48 h 达到最高值5 257.79和 1 363.94 mg/L,然后下降到一定程度后保持恒定.该菌株对麦麸长达 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,此菌株对麦麸中的纤维素、半纤维素和木质素都有不同程度的降解,但以纤维素降解为主.纤维素、半纤维素和木质素的降解率分别为 37.03 %、15.86 % 和 17.03 %.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麦麸内表面蜂巢结构边缘骨架中起支撑作用的成分.

Study on the Degradation of Wheat Bran by Bacillus licheniformis

The degradation of wheat bran by Bacillus licheniformis(Bacillus sp.X18) was studied by means of measuring concentrations of reducing sugar and soluble total sugar,activities of cellulase and hemicellulase in fermented broth,weight loss,crystallinity,FT-IR spectra and surface structure of residue.The results showed that the process of biodegradation of lignocellulose is actually simultaneous saccharification and fermentation.Cellulase and hemicellulase activities reached the highest level in 96 and 48 h,respectively.Concentrations of soluble total sugar and reducing sugar reached the highest level in 4 and 48 h,at 5 257.79 and 1 363.94 mg/L,respectively,and then decreased with time and maintained invariable value. Crystallinity of residue had no obvious change after 5 d cultivation.FT-IR spectrum of residue showed that Bacillus sp.X18 mainly degradated cellulose in wheat bran.After 5 d cultivation degradation rates of cellulose,hemicellulose and lignin in wheat bran were 37.03 %,15.86 % and 17.03 %,respectively.SEM of surface structure of degradated wheat bran by Bacillus sp.X18 showed that constituent serving function of support in framework of honeycombed structure was mainly degradated.