Bioconversion of lutein to form aroma compounds by Pantoea dispersa.

OBJECTIVES: To investigate the conversion of lutein, a carotenoid, to aroma compounds by Pantoea dispersa Y08, a lutein-degrading bacterium isolated from marigold flower residue. Bioconversion conditions, including substrate concentration, applied co-solvent and reaction time, were optimized. RESULTS: A maximum biodegradation yield of 80 % for lutein at 10 g/l was achieved. The intermediate, 3-hydroxy-ß-ionone, and final ß-ionone products were revealed by GC-MS. A bioconversion pathway of lutein is proposed to involve cleavage at the 9-10 double bond position, followed by de-hydroxylation at the 3-hydroxy position. CONCLUSIONS: This is the first report of the ability of a bacterium, P. dispersa, to sequentially convert lutein to 3-hydroxy-ß-ionone and then ß-ionone.

Pyrroloquinoline quinone biosynthesis in Escherichia coli through expression of the Gluconobacter oxydans pqqABCDE gene cluster.

We have expressed the pqqABCDE gene cluster from Gluconobacter oxydans, which is involved in pyrroloquinoline quinone (PQQ) biosynthesis, in Escherichia coli, resulting in PQQ accumulation in the medium. Since the gene cluster does not include the tldD gene needed for PQQ production, this result suggests that the E. coli tldD gene, which shows high homology to the G. oxydans tldD gene, carries out that function. The synthesis of PQQ activated d-glucose dehydrogenase in E. coli and the growth of the recombinant was improved. In an attempt to increase the production of PQQ, which acts as a vitamin or growth factor, we transformed E. coli with various recombinant plasmids, resulting in the overproduction of the PQQ synthesis enzymes and, consequently, PQQ accumulation--up to 6 mM--in the medium. This yield is 21.5-fold higher than that obtained in previous studies.