Molecular, Physiological and Phenotypic Characterization of Paracoccus denitrificans ATCC 19367 Mutant Strain P-87 Producing Improved Coenzyme Q^sub 10

Coenzyme Q^sub 10^ (CoQ^sub 10^) is a blockbuster nutraceutical molecule which is often used as an oral supplement in the supportive therapy for cardiovascular diseases, cancer and neurodegenerative diseases. It is commercially produced by fermentation process, hence constructing the high yielding CoQ^sub 10^ producing strains is a pre-requisite for cost effective production. Paracoccus denitrificans ATCC 19367, a biochemically versatile organism was selected to carry out the studies on CoQ^sub 10^ yield improvement. The wild type strain was subjected to iterative rounds of mutagenesis using gamma rays and NTG, followed by selection on various inhibitors like CoQ^sub 10^ structural analogues and antibiotics. The screening of mutants were carried out using cane molasses based optimized medium with feeding strategies at shake flask level. In the course of study, the mutant P-87 having marked resistance to gentamicin showed 1.25-fold improvements in specific CoQ^sub 10^ content which was highest among all tested mutant strains. P-87 was phenotypically differentiated from the wild type strain on the basis of carbohydrate assimilation and FAME profile. Molecular differentiation technique based on AFLP profile showed intra specific polymorphism between wild type strain and P-87. This study demonstrated the beneficial outcome of induced mutations leading to gentamicin resistance for improvement of CoQ^sub 10^ production in P. denitrificans mutant strain P-87. To investigate the cause of gentamicin resistance, rpIF gene from P-87 and wild type was sequenced. No mutations were detected on the rpIF partial sequence of P-87; hence gentamicin resistance in P-87 could not be conferred with rpIF gene. However, detecting the mutations responsible for gentamicin resistance in P-87 and correlating its role in CoQ^sub 10^ overproduction is essential. Although only 1.25-fold improvement in specific CoQ^sub 10^ content was achieved through mutant P-87, this mutant showed very interesting characteristic, differentiating it from its wild type parent strain P. denitrificans ATCC 19367, which are presented in this paper.