Shuting Zhao, Dongtao Deng, Tianzheng Wan, Jie Feng, Lei Deng, Qianyi Tian, Jiayu Wang, Umm E. Aiman, Balym Mukhaddi, Xiaofeng Hu, Shaolin Chen, Ling Qiu, Lili Huang, Yahong Wei
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引用次数: 0
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.
期刊介绍:
Biotechnology for Biofuels is an open access peer-reviewed journal featuring high-quality studies describing technological and operational advances in the production of biofuels, chemicals and other bioproducts. The journal emphasizes understanding and advancing the application of biotechnology and synergistic operations to improve plants and biological conversion systems for the biological production of these products from biomass, intermediates derived from biomass, or CO2, as well as upstream or downstream operations that are integral to biological conversion of biomass.
Biotechnology for Biofuels focuses on the following areas:
• Development of terrestrial plant feedstocks
• Development of algal feedstocks
• Biomass pretreatment, fractionation and extraction for biological conversion
• Enzyme engineering, production and analysis
• Bacterial genetics, physiology and metabolic engineering
• Fungal/yeast genetics, physiology and metabolic engineering
• Fermentation, biocatalytic conversion and reaction dynamics
• Biological production of chemicals and bioproducts from biomass
• Anaerobic digestion, biohydrogen and bioelectricity
• Bioprocess integration, techno-economic analysis, modelling and policy
• Life cycle assessment and environmental impact analysis