Morales Gabriel Murillo, Ali Sameh S, Si Haibing, Zhang Weimin, Zhang Rongxian, Hosseini Keyvan, Sun Jianzhong, Zhu Daochen
Biofuels Institute, School of Environmental Science and Safety Engineering, Jiangsu University, Zhenjiang, China.
State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.
Front Bioeng Biotechnol. 2020 Jun 30;8:671. doi: 10.3389/fbioe.2020.00671. eCollection 2020.
There is increasing interest in research on lignin biodegradation compounds as potential building blocks in applications related to renewable products. More attention is necessary to evaluate the effects of the initial pH conditions during the bacterial degradation of lignin. In this study we performed experiments on lignin biodegradation under acidic and mild alkaline conditions. For acidic biodegradation, lignin was chemically pretreated with hydrogen peroxide. Alkaline biodegradation was achieved by developing the bacterial growth on Luria and Bertani medium with alkali lignin as the sole carbon source. The mutant strain BL21(Lacc) was used to carry out lignin biodegradation over 10 days of incubation. Results demonstrated that under acidic conditions there was a predominance of aliphatic compounds of the C-C type. Alkaline biodegradation was produced in the context of oxidative stress, with a greater abundance of aryl compounds. The final pH values of acidic and alkaline biodegradation of lignin were 2.53 and 7.90, respectively. The results of the gas chromatography mass spectrometry analysis detected compounds such as crotonic acid, lactic acid and 3-hydroxybutanoic acid for acidic conditions, with potential applications for adhesives and polymer precursors. Under alkaline conditions, detected compounds included 2-phenylethanol and dehydroabietic acid, with potential applications for perfumery and anti tumor/anti-inflammatory medications. Size-exclusion chromatography analysis showed that the weight-average molecular weight of the alkaline biodegraded lignin increased by 6.75-fold compared to the acidic method, resulting in a repolymerization of its molecular structure. Lignin repolymerization coincided with an increase in the relative abundance of dehydroabietic acid and isovanillyl alcohol, from 2.70 and 3.96% on day zero to 13.43 and 10.26% on 10th day. The results of the Fourier-transformed Infrared spectroscopy detected the presence of C = O bond and OH functional group associated with carboxylic acids in the acidic method. In the alkaline method there was a greater preponderance of signals related to skeletal aromatic structures, the amine functional group and the C - O - bond. Lignin biodegradation products from BL21(Laccase), under different initial pH conditions, demonstrated a promising potential to enlarge the spectrum of renewable products for biorefinery activities.
作为可再生产品相关应用中的潜在构建模块，木质素生物降解化合物的研究越来越受到关注。在木质素细菌降解过程中，需要更多关注来评估初始pH条件的影响。在本研究中，我们在酸性和温和碱性条件下进行了木质素生物降解实验。对于酸性生物降解，木质素用过氧化氢进行化学预处理。碱性生物降解是通过在以碱木质素为唯一碳源的Luria和Bertani培养基上培养细菌来实现的。突变菌株BL21(Lacc)用于在10天的培养期内进行木质素生物降解。结果表明，在酸性条件下，C-C型脂肪族化合物占主导。碱性生物降解是在氧化应激的情况下产生的，芳基化合物的丰度更高。木质素酸性和碱性生物降解的最终pH值分别为2.53和7.90。气相色谱-质谱分析结果在酸性条件下检测到巴豆酸、乳酸和3-羟基丁酸等化合物，它们在粘合剂和聚合物前体方面有潜在应用。在碱性条件下，检测到的化合物包括2-苯乙醇和脱氢枞酸，它们在香料和抗肿瘤/抗炎药物方面有潜在应用。尺寸排阻色谱分析表明，与酸性方法相比，碱性生物降解木质素的重均分子量增加了6.75倍，导致其分子结构发生再聚合。木质素再聚合与脱氢枞酸和异香草醇的相对丰度增加同时发生，从第0天的2.70%和3.96%增加到第10天的13.43%和10.26%。傅里叶变换红外光谱结果在酸性方法中检测到与羧酸相关的C = O键和OH官能团的存在。在碱性方法中，与骨架芳香结构、胺官能团和C - O -键相关的信号占优势。在不同初始pH条件下，来自BL21(漆酶)的木质素生物降解产物显示出扩大生物炼制活动可再生产品范围的良好潜力。
