RESUMO
Adipic acid is an important dicarboxylic acid, which is an essential building block to synthesize nylon 6-6 fiber. Adipic acid is primarily synthesized from chemical plant, however, this process is associated with a number of environmental concerns including heavy pollution, toxic catalyst and harsh reaction conditions. A decent amount of adipic acid was produced by reconstructing the reversed adipate-degradation pathway (RADP) from Thermobifida fusca in Escherichia coli. However, IPTG was used in the previous study, which was not feasible in the fermentation industry. In this study, strong promoter-5'-UTR complexes (PUTR) were chosen to construct a highly efficient induction-free system to produce adipic acid. First, comparisons of various exogenous 5'-UTR Complexes, as well as a series of E. coli host strains, demonstrated that those genes using E. coli K12 MG1655 as the host strain produced the highest titer of adipic acid. Subsequently, optimizations were applied to enhance the titer of adipate biosynthesizing strains. The highest titer of adipate of 57.6 g L-1 was achieved by fed-batch fermentation. This work offers a better way to enhance the industrial titer of adipate.
Assuntos
Adipatos/metabolismo , Escherichia coli/metabolismo , Regiões 5' não Traduzidas/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Técnicas de Cultura Celular por Lotes , Escherichia coli/genética , Fermentação , Engenharia Metabólica , Redes e Vias Metabólicas/genética , Regiões Promotoras Genéticas/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Thermobifida/genética , Thermobifida/metabolismoRESUMO
Glutaric acid is an important organic acid applied widely in different fields. Most previous researches have focused on the production of glutaric acid in various strains using the 5-aminovaleric acid (AMV) or pentenoic acid synthesis pathways. We previously utilized a five-step reversed adipic acid degradation pathway (RADP) in Escherichia coli BL21 (DE3) to construct strain Bgl146. Herein, we found that malonyl-CoA was strictly limited in this strain, and increasing its abundance could improve glutaric acid production. We, therefore, constructed a malonic acid uptake pathway in E. coli using matB (malonic acid synthetase) and matC (malonic acid carrier protein) from Clover rhizobia. The titer of glutaric acid was improved by 2.1-fold and 1.45-fold, respectively, reaching 0.56 g/L and 4.35 g/L in shake flask and batch fermentation following addition of malonic acid. Finally, the highest titer of glutaric acid was 6.3 g/L in fed-batch fermentation at optimized fermentation conditions.