Manipulation of Purine Metabolic Networks for Riboflavin Production in Bacillus subtilis

Abstract

Guanosine monophosphate, the precursor for riboflavin biosynthesis, can be converted to or generated from other purine compounds in purine metabolic networks. In this study, genes in these networks were manipulated in a riboflavin producer, Bacillus subtilis R, to test their contribution to riboflavin biosynthesis. Knocking out adenine phosphoribosyltransferase (apt), xanthine phosphoribosyltransferase (xpt), and adenine deaminase (adeC) increased the riboflavin production by 14.02, 6.78, and 41.50%, respectively, while other deletions in the salvage pathway, interconversion pathway, and nucleoside decomposition genes have no positive effects. The enhancement of riboflavin production in apt and adeC deletion mutants is dependent on the purine biosynthesis regulator PurR. Repression of ribonucleotide reductases (RNRs) led to a 13.12% increase of riboflavin production, which also increased in two RNR regulator mutants PerR and NrdR by 37.52 and 8.09%, respectively. The generation of deoxyribonucleoside competed for precursors with riboflavin biosynthesis, while other pathways do not contribute to the supply of precursors; nevertheless, they have regulatory effects.

RNA-Seq Provides New Insights into the Gene Expression Changes in Azoarcus olearius BH72 under Nitrogen-Deficient and Replete Conditions beyond the Nitrogen Fixation Process

“…Therefore, reduced flux through PPP under N 2 -fixing conditions might be responsible for the repression of riboflavin and cobalamin synthesis. The relationship between GTP availability and riboflavin synthesis has been elucidated in Bacillus subtilis [ 65 , 66 ]. In these studies, riboflavin production was enhanced by deregulating the purine pathway and by suppressing ribonucleotide reductase, which competes for the GTP precursor.…”

Dynamic Control Strategy to Produce Riboflavin with Lignocellulose Hydrolysate in the Thermophile Geobacillus thermoglucosidasius

“…Therefore, G. thermoglucosidasius DSM 2542 is emerging as an attractive platform for biofermentation. Other strategies, including deletion of the regulatory gene ccpN (gene encoding the lactic dehydrogenase) and certain genes involved in the purine metabolic network, 17,41 engineering of the riboswitches of pur and rib operons, 42 and the RBS regions of genes involved in riboflavin biosynthesis, 43 introducing mutations in the transcriptional regulators CcpN and YvrH, 44 and overexpression genes involved in the pentose-phosphate pathway including zwf, gnd, ykgB, and gntZ, 45 have also been successful in increasing the production of riboflavin. These approaches might be integrated with our GCR-DC strategy to further improve the capacity of this robust host, G. thermoglucosidasius DSM 2542, to utilize natural carbon sources for the production of riboflavin in future.…”

A dynamic control strategy to produce riboflavin with lignocellulose hydrolysate in the thermophile Geobacillus thermoglucosidasius

“…Therefore, G. thermoglucosidasius DSM 2542 is emerging as an attractive platform for biofermentation. Other strategies, including deletion of the regulatory gene ccpN, gene encoding lactic dehydrogenase and certain genes involved in the purine metabolic network 21,57 , engineering of the riboswitches of pur and rib operons 58 and the RBS regions of genes involved in ribo avin biosynthesis 59 , and introducing mutations in the transcriptional regulators CcpN and YvrH 16 , have also been successful to increase the production of ribo avin. These approaches might be integrated with our GCR-DC strategy to further improve the capacity of this robust host, G. thermoglucosidasius DSM 2542, to utilize natural carbon sources for the production of ribo avin and other high-value products in future.…”