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Biotransformation of phenol to glutamate by Corynebacterium glutamicum
ATCC 13032: molecular and biochemical studies

1 B Jaya Bhargavi*, B Muralidhara Rao
1

1 Department of Biotechnology, Sri Krishnadeveraya University, Anantapuram-515003, India.

Corresponding author: bargaviphd@gmail.com

Abstract:

The present study aimed to investigate the biotransformation of phenol to glutamate by C. glutamicum
using molecular and biochemical studies. At the molecular level, the effect of phenol on mRNA
expression levels of genes associated with phenol degradation pathway [transcriptional regulator AraC
family member pheR, phenol hydroxylase (phe), catechol 1,2-dioxygenase (catA)], TCA cycle [2-
oxoglutarate dehydrogenase (odhA)], glutamate synthesis [glutamate dehydrogenase (gdh)], stress
response [dihydrolipoamide dehydrogenase (lpd) and L-transpeptidase (lpps)], fatty acid synthesis [beta
subunit of homolog of acetyl CoA carboxylase or detergent sensitivity rescuer (dtsR1)] and regulator
of 2-oxoglutarate dehydrogenase [serine/threonine protein kinase (pknG)] in C. glutamicum grown on
phenol medium under two experimental conditions: 200 ppm phenol plus 1% yeast extract and 300 ppm
phenol plus 1.1% yeast extract was investigated. The results indicated that significant up-regulation of
pheR, phe, catA, lpps, lpd and gdh is associated with significant down-regulation of odhA, dtsR1 and
pknG was observed in C. glutamicum grown on phenol medium over bacteria grown on yeast extract
alone. Further, biochemical studies indicated that the activity levels of 2-oxoglutarate dehydrogenase
were significantly reduced, while significant elevation in the activity levels of glutamate dehydrogenase
was observed in cell-free extracts of C. glutamicum grown on phenol medium over controls. The results
also indicated that the C. glutamicum utilize phenol as carbon and energy source thereby promote
glutamate synthesis as evidenced by a significant increase in the glutamate levels in the medium. To
conclude, environmental pollution caused by phenol is of major concern and to mitigate the phenol
toxicity, eco-friendly approaches are needed. The current study highlights the phenol degradation
potential of C. glutamicum and its transformation to glutamate. The results were discussed in the light
of literature.

Keywords: C. glutamicum, Growth, Glutamate, Phenol yeast extract