Project description:Xanthan gum, a natural heteropolysaccharide produced by Xanthomonas species, has many biotechnological applications across industries due to its unique rheological properties. Expanding its utility requires specific enzymes capable of targeted xanthan modification or degradation. In this study, a novel bacterial strain, isolated from a spoiled xanthan sample and identified as Paenibacillus taichungensis I5, was shown to degrade xanthan using a plate screening assay with Congo red. Enzyme activity tests of the culture supernatant demonstrated the secretion of xanthan-degrading enzymes. Genome and proteome analyses suggests a chromosomal xanthan utilization locus encoding a suite of enzymes, including a xanthanase (Pt_XanGH9), two xanthan lyases (Pt_XanPL8a and Pt_XanPL8b), two unsaturated glucuronidases, two α-mannosidases, as well as transport and regulator proteins. Functional characterization through recombinant protein expression and enzyme assays confirmed the functions of Pt_XanGH9, Pt_XanPL8a and Pt_XanPL8b on native xanthan and xanthan-derived oligosaccharides. The polysaccharide degradation products released by these enzymes were identified via LC-MS analysis. The two xanthan lyases differed in cleavage specificity. In contrast to Pt_XanPL8a, Pt_XanPL8b is synthesized with an N-terminal signal peptide, yet both lyases were detected in cell-free supernatant during growth on xanthan. Based on the composition of the xanthan utilization gene cluster and preliminary enzyme characteristics, a working model for xanthan utilization by P. taichungensis I5 is proposed. Reaching a better understanding of bacterial xanthan derivatives and xanthan degrading pathways and the enzymes involved may help to develop modified xanthan derivatives and xanthan degrading enzymes that align with the specific demands of various industrial process.
Project description:The consortium biomass was obtained from a mesophilic fed-batch reactor enriched with a mixture of WAS and uronic acids-degrading bacteria.
Project description:A novel Paenarthrobacter ilicis 6C isolate from soil found in Bielefeld, Germany, was sequenced and characterized by proteome analysis to provide the first clear look at a novel genus in the realm of xanthan degrading microorganisms. This research provides additional groundwork for the ongoing characterization of Paenarthrobacter, as well as widening the understanding of xanthan degrading microorganisms.
Project description:A new strain of xanthan-degrading bacteria identified as Cohnella sp. has been isolated from a xanthan thickener for food production. The strain was able to utilize xanthan as the only carbon source and reduce the viscosity of the xanthan-containing medium during cultivation. Xanthan hydrolytic activity was revealed by congo red staining after growth of the strain on agar plates containing xanthan. By analyzing the secretome of Cohnella sp. after growth on different media (lysogeny broth, glucose mineral medium, xanthan mineral medium), a xanthanase designated as CspXan9 was found and its gene was successfully expressed in Escherichia coli Rosetta2. CspXan9 could efficiently degrade the -1,4-glucan backbone of xanthan after previous removal of pyruvylated mannose residues from the ends of the native xanthan side chains by xanthan lyase treatment (XLT-xanthan). Compared with a known xanthanase from Paenibacillus nanensis, the modular xanthanase CspXan9 had a different module composition at the N- and C-terminal ends. High-performance anion-exchange chromatography (HPAEC-PAD) analysis revealed that the main putative end products released from XLT-xanthan by CspXan9 hydrolysis were tetrasaccharides. Deletion derivatives lacking some of the non-catalytic domains (CspXan9-C, CspXan9-N, CspXan9-C-N) were produced in E. coli to explore the functions of the N- and C-terminal regions of the enzyme. Enzyme assays with the purified deletion derivatives, which all contained the catalytic glycoside hydrolase family 9 (GH9) module, resulted in a range of specific activities on XLT-xanthan between 10.31 ± 0.29 U/mg (CspXan9-C) and 1.38 ± 0.05 U/mg (CspXan9-C-N). Mobility shift assays performed by native affinity polyacrylamide gel electrophoresis (NAPAGE) in the presence of different polysaccharides indicated that the C-terminal module of CspXan9 represents a novel carbohydrate-binding module of CBM66 with binding affinity for XLT-xanthan. The only previously known binding function of a member of the CBM66 family is exo-type binding to the non-reducing fructose ends of the -fructan polysaccharides inulin and levan.