Formate as a supplementary substrate facilitates sugar metabolism and solvent production by Clostridium beijerinckii NCIMB 8052

Microbial utilization and conversion of organic one-carbon compounds,such as formate and methanol that can be easily produced from CO_(2),has emerged as an attractive approach for biorefinery.In this study,we discovered Clostridium beijerinckii NCIMB 8052,a typical solventogenic Clostridium strain,to be a native formate-utilizing bacterium.^(13)C isotope analysis showed that formate could be metabolized via both assimilation and dissimi-lation pathways in C.beijerinckii NCIMB 8052.Notably,the use of formate as the supplementary substrate by this strain could significantly enhance its glucose consumption and ABE(acetone-butanol-ethanol)production,largely due to the up-regulation of genes responsible for glycolysis and glucose transport under formate stress.Based on these findings,we further improved formate tolerance of C.beijerinckii NCIMB 8052 by adaptive lab-oratory evolution,generating an evolved strain Cbei-FA01.The Cbei-FA01 strain could produce 23.0 g/L of ABE solvents using glucose and formate as dual substrates,~50%higher than that of the wild-type strain under the same condition.Moreover,such a promotion effect of formate on ABE production by Cbei-FA01 was also observed in fermenting a glucose-xylose mixture.This work reveals a previously unreported role of formate in biological ABE production,providing a new approach to utilize this one-carbon source.