| Phenylpropanoids and flavonoids have presented a plenty of biological activities and pharmacological activities,such as antioxidant,anticancer,anti-inflammatory,antibiotic,etc.Moreover,they also play an important role among cosmetics industry and food industry.As p-coumaric acid is the precursor compound in the biosynthesis of phenylpropanoids and flavonoids,its biosynthesis also attract more attention in recent years.Three compounds had been chosen to be representative in the biosynthesis of phenylpropanoids and flavonoids in this study.Firstly,an p-coumaric acid overproducing Saccharomyces cerevisiae was constructed in our study,on this basis,Ltyrosine feedback inhibition related genes ARO4 and ARO7 were overexpressed,furthermore,the by-products pathway related genes ARO10 and PDC5 was knocked out by loxP-Cre system.After these modifications,the production of p-coumaric acid was improved by 2.05 fold,up to 87.56 mg/L.Besides,we also explored the effects of concentration of added tyrosine on the production of p-coumaric.When 1 mM Ltyrosine was added,the production of p-coumaric acid arrived the peak,about 174.57±0.30 mg/L.Secondly,caffeic acid was chosen as the representative compound of the phenylpropanoids,it was found that the production of caffeic acid was increased with the growing gene copies.Caused of the suitability between different gene sources and chassis strain,nine sources of hpaB and seven sources of hpa C were co-expressed in the S.cerevisiae with TAL.It was demonstrated that combined expression of different sources really showed big difference.The strain carrying hpa B from Pseudomonas aeruginosa and hpa C from Escherichia coli achieved the highest titer of caffeic acid(37.61 mg/L).As to the flavonoids,naringenin was selected to be the research target.To improve the production of naringenin,co-culture of naringenin producing S.cerevisiae and tyrosine producing Escherichia coli was utilized in our study.Through the optimization of medium,the inoculation size and inoculation ratio of two strains,a higher titer of 21.16 mg/L was obtained,which was eight times to the mono-culture one.This study has a certain preference value for the biosynthesis of p-coumaric acid and the representative compounds caffeic acid and naringenin in the future. |
