Effects of aromatic amino acids on the biosynthesis of CoQ_(10) in Rhodopseudomonas palustris

CoQ 10 has been used not only as a drug but also as a food supplement because of its various physiological and biochemical activities.Microbial fermentation is a main way for the commercial production of CoQ 10.The quinoid nucleus of CoQ 10 and aromatic amino acids are synthesized from the shikimate pathway in bacteria and there are some effects of them on another biosynthesis.The impacts of aromatic amino acids on the biosynthesis of CoQ 10 in Rhodopseudomnas palustris J001 were investigated with feeding aromatic amino acids at the end of the logarithmic phase during incubation.The results showed that the feeding of tryptophan(above 15 mg/L) strongly repressed the biosynthesis of CoQ 10.There were also some slightly unfavorable effects of feeding of phenylalanine(50 mg/L) and tyrosine(above 200 mg/L) on the biosynthesis of CoQ 10.However,the biosynthesis of CoQ 10 could be enhanced by feeding phenylalanine(above 75 mg/L) or tyrosine(from 75 to 175 mg/L).The content of CoQ 10 in the strain was found to be the highest up to(25.6±1.3) mg CoQ 10 /g dried biomass when feeding phenylalanine(100 mg/L)+tyrosine(150 mg/L),which was 52.2% higher than that in the control with no additional amino acids in the medium.The results indicated that the biosynthesis of CoQ 10 was affected by the three aromatic amino acids.It can be concluded that the biosynthesis of CoQ 10 in strain is favorable by feeding appropriate amount of phenylalanien and tyrosine without tryptophan.