Hatzinikolaou, D. G. | bioRxiv Science

bioRxiv2022

The interplay between sulfur metabolism and desulfurization profile in Rhodococcus: Unraveling the role of the transsulfuration pathway

Biodesulfurization (BDS) is a process that selectively removes sulfur from dibenzothiophene and its derivatives. Several natural biocatalysts have been isolated, all harboring the highly conserved desulfurization operon dszABC. Even though the desulfurization phenotype is known to be significantly repressed by methionine, cysteine, and inorganic sulfate, the available information on the metabolic regulation of gene expression is still limited. In this study, scarless knockouts of the sulfur metabolism-related cbs and metB genes are constructed in the desulfurizing strain Rhodococcus sp. IGTS8. We provide sequence analyses for both enzymes of the reverse transsulfuration pathway and report their involvement in the sulfate- and methionine-dependent repression of the biodesulfurization phenotype, based on desulfurization assays in the presence of different sulfur sources. Additionally, the positive effect of cbs and metB gene deletions on dsz gene expression in the presence of both sulfate and methionine, but not cysteine, is uncovered and highlighted.

microbiology↗

bioRxiv2020

Microbial bioprospecting for lignocellulose degradation at a unique Greek environment

Bacterial systems have gained wide attention for depolymerization of lignocellulosic biomass, due to their high functional diversity and adaptability. To achieve the full microbial exploitation of lignocellulosic residues and the cost-effective production of bioproducts within a biorefinery, multiple metabolic pathways and enzymes of various specificities are required. In this work, highly diverse aerobic, mesophilic bacteria enriched from Keri Lake, a pristine marsh of increased biomass degradation and natural underground oil leaks, were explored for their metabolic versatility and enzymatic potential towards lignocellulosic substrates. A wide diversity of Pseudomonas species were obtained from enrichment cultures where organosolv lignin served as the sole carbon and energy source and were able to assimilate a range of lignin-associated aromatic compounds. Highly complex bacterial consortia were also enriched in cultures with xylan or carboxymethyl cellulose as sole carbon sources, belonging to Actinobacteria, Proteobacteria, Bacilli, Sphingobacteriia, and Flavobacteria. Numerous individual isolates could target diverse structural lignocellulose polysaccharides by expressing hydrolytic activities on crystalline or amorphous cellulose and xylan. Specific isolates showed increased potential for growth in lignin hydrolysates prepared from alkali pretreated agricultural wastes. The results suggest that Keri isolates represent a pool of effective lignocellulose degraders with significant potential for industrial applications in a lignocellulose biorefinery.

microbiology↗