title: Carbon Source-Dependent Inducible Metabolism of Veratryl Alcohol and Ferulic Acid in Pseudomonas putida CSV86.
abstract: Pseudomonas putidaCSV86 degrades lignin-derived metabolic intermediates,viz, veratryl alcohol, ferulic acid, vanillin, and vanillic acid, as the sole sources of carbon and energy. Strain CSV86 also degraded lignin sulfonate. Cell respiration, enzyme activity, biotransformation, and high-pressure liquid chromatography (HPLC) analyses suggest that veratryl alcohol and ferulic acid are metabolized to vanillic acid by two distinct carbon source-dependent inducible pathways. Vanillic acid was further metabolized to protocatechuic acid and entered the central carbon pathway via the β-ketoadipate route afterorthoring cleavage. Genes encoding putative enzymes involved in the degradation were found to be present atfer,ver, andvanloci. The transcriptional analysis suggests a carbon source-dependent cotranscription of these loci, substantiating the metabolic studies. Biochemical and quantitative real-time (qRT)-PCR studies revealed the presence of two distinctO-demethylases,viz, VerAB and VanAB, involved in the oxidative demethylation of veratric acid and vanillic acid, respectively. This report describes the various steps involved in metabolizing lignin-derived aromatic compounds at the biochemical level and identifies the genes involved in degrading veratric acid and the arrangement of phenylpropanoid metabolic genes as three distinct inducible transcription units/operons. This study provides insight into the bacterial degradation of lignin-derived aromatics and the potential ofP. putidaCSV86 as a suitable candidate for producing valuable products.IMPORTANCEPseudomonas putidaCSV86 metabolizes lignin and its metabolic intermediates as a carbon source. Strain CSV86 displays a unique property of preferential utilization of aromatics, including for phenylpropanoids over glucose. This report unravels veratryl alcohol metabolism and genes encoding veratric acidO-demethylase, hitherto unknown in pseudomonads, thereby providing new insight into the metabolic pathway and gene pool for lignin degradation in bacteria. The biochemical and genetic characterization of phenylpropanoid metabolism makes it a prospective system for its application in producing valuable products, such as vanillin and vanillic acid, from lignocellulose. This study supports the immense potential ofP. putidaCSV86 as a suitable candidate for bioremediation and biorefinery.
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, India.
authors.forename: Karishma
authors.initials: K
authors.lastname: Mohan
authors.affiliation: Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, India pphale@iitb.ac.in.
authors.forename: Prashant S
authors.initials: PS
authors.lastname: Phale
mesh_terms: D001547:Benzaldehydes / Q000378:metabolism; D001592:Benzyl Alcohols / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002244:Carbon / Q000378:metabolism*; D003373:Coumaric Acids / Q000378:metabolism*; D020869:Gene Expression Profiling; D062385:Hydroxybenzoates / Q000378:metabolism; D008031:Lignin / Q000737:chemistry / Q000378:metabolism; D010090:Oxidoreductases, O-Demethylating / Q000235:genetics / Q000378:metabolism; D011446:Prospective Studies; D016958:Pseudomonas putida / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D014641:Vanillic Acid / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D001547:Benzaldehydes; D001592:Benzyl Alcohols; D003373:Coumaric Acids; D062385:Hydroxybenzoates; C036909:lignocellulose; C009333:veratric acid; C009091:protocatechuic acid; D002244:Carbon; D008031:Lignin; C004999:ferulic acid; C100058:vanillin; D010090:Oxidoreductases, O-Demethylating; D014641:Vanillic Acid; C042197:veratryl alcohol
keywords: O-demethylase; Pseudomonas; enzyme induction; phenylpropanoid metabolism; transcription analysis; veratryl alcohol degradation