ABSTRACT
The oxygenated ß-carotene derivative astaxanthin exhibits outstanding colouring, antioxidative and health-promoting properties and is mainly found in the marine environment. To satisfy the growing demand for this ketocarotenoid in the feed, food and cosmetics industries, there are strong efforts to develop economically viable bioprocesses alternative to the current chemical synthesis. However, up to now, natural astaxanthin from Haematococcus pluvialis, Phaffia rhodozyma or Paracoccus carotinifaciens has not been cost competitive with chemically synthesized astaxanthin, thus only serving niche applications. This review illuminates recent advances made in elucidating astaxanthin biosynthesis in P. rhodozyma. It intensely focuses on strategies to increase astaxanthin titers in the heterobasidiomycetous yeast by genetic engineering of the astaxanthin pathway, random mutagenesis and optimization of fermentation processes. This review emphasizes the potential of P. rhodozyma for the biotechnological production of astaxanthin in comparison to other natural sources such as the microalga H. pluvialis, other fungi and transgenic plants and to chemical synthesis.
Subject(s)
Basidiomycota/metabolism , Biotechnology/methods , Fermentation , Genetic Engineering , Metabolic Networks and Pathways/genetics , Mutagenesis , Xanthophylls/metabolismABSTRACT
A comprehensive taxonomic re-evaluation was performed on the marine, zeaxanthin-producing bacterium formerly classified as [Favobacterium] sp. strain R-1 512 (ATCC 21588). This strain, together with two other previously described marine isolates, [Flavobacterium] strain R-1506 and Paracoccus sp. strain MBIC 3966, were found to comprise a new species of the genus Paracoccus. The name Paracoccus zeaxanthinifaciens sp. nov. is proposed, with ATCC 21588T (= R-1512T =LMG 21293T) designated as the type strain.
Subject(s)
Paracoccus/classification , Paracoccus/metabolism , beta Carotene/analogs & derivatives , beta Carotene/biosynthesis , Base Composition , Base Sequence , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/genetics , Fatty Acids/analysis , Molecular Sequence Data , Paracoccus/genetics , Phenotype , Phylogeny , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , Species Specificity , Xanthophylls , ZeaxanthinsABSTRACT
The genes coding for all the enzymes involved in the conversion of acetyl-CoA to farnesyl diphosphate (FPP) in the zeaxanthin-producing bacterium Paracoccus zeaxanthinifaciens were cloned and characterized. Two genes encoding enzymes catalysing the condensation of two acetyl-CoA molecules to acetoacetyl-CoA were found. The six enzymes involved in the conversion of acetyl-CoA and acetoacetyl-CoA to isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) are grouped in an operon, designated the mevalonate operon. The gene encoding the enzyme catalysing two consecutive condensations, IPP and DMAPP to geranyl diphosphate (GPP) and IPP and GPP to FPP, is not clustered with any other gene encoding an enzyme of the isoprenoid pathway. Genes encoding enzymes involved in the biosynthesis of poly-hydroxyalkanoate and non-carotenoid isoprenoids found in P. zeaxanthinifaciens are also presented.
Subject(s)
Hemiterpenes , Membrane Proteins , Paracoccus/genetics , Terpenes/metabolism , Acetyl Coenzyme A/metabolism , Acyl Coenzyme A/metabolism , Amino Acid Sequence , Bacterial Proteins/genetics , Carbon-Carbon Double Bond Isomerases/genetics , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Bacterial/isolation & purification , Hydroxymethylglutaryl CoA Reductases/genetics , Mevalonic Acid/metabolism , Molecular Sequence Data , Organophosphorus Compounds/metabolism , Paracoccus/enzymology , Paracoccus/metabolism , Polyisoprenyl Phosphates/metabolism , Sequence Alignment , Sequence Analysis, DNA , Sequence Homology, Amino Acid , SesquiterpenesABSTRACT
Cultures of the zeaxanthin-producing bacterium Paracoccus species strain PTA-3335 (formerly Flavobacterium) were grown with supplements of (13)C-labeled glucose. Zeaxanthin was isolated and analyzed by (13)C NMR spectroscopy. The data showed that the isoprenoid precursors of zeaxanthin were biosynthesized via the mevalonate pathway. The microorganism was found to utilize glucose mainly via the Entner-Doudoroff pathway.
