Biofuels Institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, PR China; Department of Computer Science, University of Agriculture, Faisalabad, 38040, Pakistan.
Biofuels Institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, PR China.
Chemosphere. 2023 Jan;310:136754. doi: 10.1016/j.chemosphere.2022.136754. Epub 2022 Oct 10.
Lignin is the most abundant heterogeneous aromatic polymer present on planet Earth and is recalcitrant to degradation due to its complex structure, therefore, imposing a challenge to biorefinery procedures. Identifying new microbial strains with the potential to valorize lignin into useful compounds is indispensable to achieving green sustainable consumption. In this study, a novel Pseudomonas strain designated as Hu109A was isolated from the termite gut and the genome was sequenced and analyzed further. The genome contains a circular chromosome with the size of 5,131,917 bp having a GC content of 62.6% and 4698 genes. Genome annotation reveals that the strain possesses lignin-oxidizing enzymes such as DyP-type peroxidases, laccase, dioxygenase, and aromatic degradation gene clusters. The genome also contains O-methyltransferases which function in accelerating the lignin degradation by methylating the free hydroxyl phenolic compounds which in high concentration can inhibit the lignin peroxidase. Furthermore, the genome exhibits two gene clusters encoding the enzymes related to polyhydroxyalkanoates (PHA) synthesis. Pseudomonas strains are generally assumed to produce medium chain length PHAs (mcl-PHAs) only, however, strain Hu109A contains both Class II PHA synthase genes involved in mcl-PHAs and Class III PHA synthase gene involved in short-chain length PHAs (scl-PHAs). Gas Chromatography-Mass Spectrometry (GC-MS) analysis showed that using 1 g/L lignin as the sole carbon source, the maximum production of PHA observed was 103.68 mg/L, which increased to 186 mg/L with an increase in lignin concentration to 3 g/L. However, PHA production while using glucose as the sole carbon source was significantly lower than the lignin source, and maximum production was 125.6 mg/L with 3 g/L glucose. The strain Hu109A can tolerate a broad range of solvents including methanol, isopropanol, dimethylformamide, and ethanol, revealing its potential for industrial applications.
木质素是地球上最丰富的异质芳香族聚合物，由于其复杂的结构，难以降解，因此对生物炼制过程构成了挑战。鉴定具有将木质素转化为有用化合物潜力的新微生物菌株对于实现绿色可持续消费是必不可少的。在这项研究中，从白蚁肠道中分离出一株新型假单胞菌菌株，命名为 Hu109A，并对其基因组进行了测序和进一步分析。该基因组包含一个大小为 5131917bp 的圆形染色体，GC 含量为 62.6%，包含 4698 个基因。基因组注释表明，该菌株具有木质素氧化酶，如 DyP 型过氧化物酶、漆酶、双加氧酶和芳香族降解基因簇。该基因组还包含 O-甲基转移酶，其通过甲基化高浓度的游离羟基酚化合物来加速木质素降解，高浓度的游离羟基酚化合物会抑制木质素过氧化物酶。此外，基因组还显示出两个编码与聚羟基烷酸（PHA）合成相关酶的基因簇。假单胞菌通常被认为只产生中链长 PHAs（mcl-PHAs），然而，菌株 Hu109A 既包含参与 mcl-PHAs 合成的 II 类 PHA 合酶基因，也包含参与短链长 PHAs（scl-PHAs）合成的 III 类 PHA 合酶基因。气相色谱-质谱联用（GC-MS）分析表明，以 1g/L 木质素作为唯一碳源，观察到 PHA 的最大产量为 103.68mg/L，当木质素浓度增加到 3g/L 时，PHA 的产量增加到 186mg/L。然而，当以葡萄糖作为唯一碳源时，PHA 的产量明显低于木质素源，最大产量为 125.6mg/L，葡萄糖浓度为 3g/L。菌株 Hu109A 可以耐受甲醇、异丙醇、二甲基甲酰胺和乙醇等多种溶剂，显示出其在工业应用中的潜力。
