PDF(Pubmed)
Abstract：
BACKGROUND: Bioconversion of plant biomass into biofuels and bio-products produces large amounts of lignin. The aromatic biopolymers need to be degraded before being converted into value-added bio-products. Microbes can be environment-friendly and efficiently degrade lignin. Compared to fungi, bacteria have some advantages in lignin degradation, including broad tolerance to pH, temperature, and oxygen and the toolkit for genetic manipulation.
RESULTS: Our previous study isolated a novel ligninolytic bacterial strain Erwinia billingiae QL-Z3. Under optimized conditions, its rate of lignin degradation was 25.24% at 1.5 g/L lignin as the sole carbon source. Whole genome sequencing revealed 4556 genes in the genome of QL-Z3. Among 4428 protein-coding genes are 139 CAZyme genes, including 54 glycoside hydrolase (GH) and 16 auxiliary activity (AA) genes. In addition, 74 genes encoding extracellular enzymes are potentially involved in lignin degradation. Real-time PCR quantification demonstrated that the expression of potential ligninolytic genes were significantly induced by lignin. 8 knock-out mutants and complementary strains were constructed. Disruption of the gene for ELAC_205 (laccase) as well as EDYP_48 (Dyp-type peroxidase), ESOD_1236 (superoxide dismutase), EDIO_858 (dioxygenase), EMON_3330 (monooxygenase), or EMCAT_3587 (manganese catalase) significantly reduced the lignin-degrading activity of QL-Z3 by 47-69%. Heterologously expressed and purified enzymes further confirmed their role in lignin degradation. Fourier transform infrared spectroscopy (FTIR) results indicated that the lignin structure was damaged, the benzene ring structure and groups of macromolecules were opened, and the chemical bond was broken under the action of six enzymes encoded by genes. The abundant enzymatic metabolic products by EDYP_48, ELAC_205 and ESOD_1236 were systematically analyzed via liquid chromatography-mass spectrometry (LC-MS) analysis, and then provide a speculative pathway for lignin biodegradation. Finally, The activities of ligninolytic enzymes from fermentation supernatant, namely, LiP, MnP and Lac were 367.50 U/L, 839.50 U/L, and 219.00 U/L by orthogonal optimization.
CONCLUSIONS: Our findings provide that QL-Z3 and its enzymes have the potential for industrial application and hold great promise for the bioconversion of lignin into bioproducts in lignin valorization.
RESULTS: Our previous study isolated a novel ligninolytic bacterial strain Erwinia billingiae QL-Z3. Under optimized conditions, its rate of lignin degradation was 25.24% at 1.5 g/L lignin as the sole carbon source. Whole genome sequencing revealed 4556 genes in the genome of QL-Z3. Among 4428 protein-coding genes are 139 CAZyme genes, including 54 glycoside hydrolase (GH) and 16 auxiliary activity (AA) genes. In addition, 74 genes encoding extracellular enzymes are potentially involved in lignin degradation. Real-time PCR quantification demonstrated that the expression of potential ligninolytic genes were significantly induced by lignin. 8 knock-out mutants and complementary strains were constructed. Disruption of the gene for ELAC_205 (laccase) as well as EDYP_48 (Dyp-type peroxidase), ESOD_1236 (superoxide dismutase), EDIO_858 (dioxygenase), EMON_3330 (monooxygenase), or EMCAT_3587 (manganese catalase) significantly reduced the lignin-degrading activity of QL-Z3 by 47-69%. Heterologously expressed and purified enzymes further confirmed their role in lignin degradation. Fourier transform infrared spectroscopy (FTIR) results indicated that the lignin structure was damaged, the benzene ring structure and groups of macromolecules were opened, and the chemical bond was broken under the action of six enzymes encoded by genes. The abundant enzymatic metabolic products by EDYP_48, ELAC_205 and ESOD_1236 were systematically analyzed via liquid chromatography-mass spectrometry (LC-MS) analysis, and then provide a speculative pathway for lignin biodegradation. Finally, The activities of ligninolytic enzymes from fermentation supernatant, namely, LiP, MnP and Lac were 367.50 U/L, 839.50 U/L, and 219.00 U/L by orthogonal optimization.
CONCLUSIONS: Our findings provide that QL-Z3 and its enzymes have the potential for industrial application and hold great promise for the bioconversion of lignin into bioproducts in lignin valorization.
摘要：
背景：将植物生物质生物转化为生物燃料和生物产品会产生大量的木质素。芳族生物聚合物在转化为增值生物产品之前需要降解。微生物可以是环境友好的并且可以有效地降解木质素。与真菌相比，细菌在木质素降解中具有一定的优势，包括对pH的广泛耐受性，温度,氧气和遗传操作的工具包。
结果：我们先前的研究分离出了一种新的木质素降解细菌菌株欧文氏菌QL-Z3。在优化条件下，以1.5g/L木质素为唯一碳源时，木质素降解率为25.24%。全基因组测序显示QL-Z3基因组中有4556个基因。在4428个蛋白质编码基因中，有139个CAZyme基因，包括54个糖苷水解酶（GH）和16个辅助活性（AA）基因。此外,74个编码胞外酶的基因可能参与木质素降解。实时PCR定量表明，木质素显着诱导了潜在的木质素降解基因的表达。构建了8个敲除突变体和互补菌株。破坏ELAC_205（漆酶）和EDYP_48（Dyp型过氧化物酶）的基因，ESOD_1236(超氧化物歧化酶),EDIO_858(双加氧酶)，EMON_3330(单加氧酶)，或EMCAT_3587（锰过氧化氢酶）可将QL-Z3的木质素降解活性显着降低47-69％。异源表达和纯化的酶进一步证实了它们在木质素降解中的作用。傅里叶变换红外光谱(FTIR)结果表明木质素结构被破坏,打开了大分子的苯环结构和基团，化学键在基因编码的六种酶的作用下断裂。通过液相色谱-质谱(LC-MS)分析,系统分析了EDYP_48、ELAC_205和ESOD_1236的丰富酶代谢产物,然后提供木质素生物降解的推测途径。最后,发酵上清液中木质素分解酶的活性，即,LiP,MnP和Lac为367.50U/L，839.50U/L,和219.00U/L正交优化。
结论：我们的发现表明，QL-Z3及其酶具有工业应用的潜力，并且在木质素的价值化中将木质素生物转化为生物产品具有广阔的前景。
结果：我们先前的研究分离出了一种新的木质素降解细菌菌株欧文氏菌QL-Z3。在优化条件下，以1.5g/L木质素为唯一碳源时，木质素降解率为25.24%。全基因组测序显示QL-Z3基因组中有4556个基因。在4428个蛋白质编码基因中，有139个CAZyme基因，包括54个糖苷水解酶（GH）和16个辅助活性（AA）基因。此外,74个编码胞外酶的基因可能参与木质素降解。实时PCR定量表明，木质素显着诱导了潜在的木质素降解基因的表达。构建了8个敲除突变体和互补菌株。破坏ELAC_205（漆酶）和EDYP_48（Dyp型过氧化物酶）的基因，ESOD_1236(超氧化物歧化酶),EDIO_858(双加氧酶)，EMON_3330(单加氧酶)，或EMCAT_3587（锰过氧化氢酶）可将QL-Z3的木质素降解活性显着降低47-69％。异源表达和纯化的酶进一步证实了它们在木质素降解中的作用。傅里叶变换红外光谱(FTIR)结果表明木质素结构被破坏,打开了大分子的苯环结构和基团，化学键在基因编码的六种酶的作用下断裂。通过液相色谱-质谱(LC-MS)分析,系统分析了EDYP_48、ELAC_205和ESOD_1236的丰富酶代谢产物,然后提供木质素生物降解的推测途径。最后,发酵上清液中木质素分解酶的活性，即,LiP,MnP和Lac为367.50U/L，839.50U/L,和219.00U/L正交优化。
结论：我们的发现表明，QL-Z3及其酶具有工业应用的潜力，并且在木质素的价值化中将木质素生物转化为生物产品具有广阔的前景。
