Effect of ferulic acid on Clostridium beijerinckii NCIMB 8052 transcriptome

The impacts of ferulic acid, a phenolic compound commonly found in lignin hydrolysates, on the growth, solvent production and transcriptional responses of C. beijerinckii NCIMB 8052 were determined. Addition of ferulic acid to growing cultures resulted in a decrease in the growth and solvent production by 30 and 25%, respectively, when compared to the control cultures. To better understand the toxicity of this compound, microarray analyses were performed using samples taken from these cultures at three different growth states. Several gene ontology terms and KEGG pathways were identified showing significant change at each status, including ABC transporters, two component system and oxidoreductase activity. Moreover, genes related with efflux systems and heat shock proteins were also strongly up- regulated. Among these, expression of the groESL operon was induced by more than 4-fold and was consequently selected for overexpression to improve C. beijerinckii tolerance to ferulic acid. Clostridium beijerinckii NCIMB 8052 was anaerobically pre-cultured in P2 media at 37°C for 9 hours to reach an optical density (OD) at 600nm of 2.0. Then, the culture was transferred to fresh media with or without 0.5 g/L of ferulic acid and cultured for 84 hours. During culturing, the samples were taken from the culture at OD 0.3, 1.4 and 5, which were used to prepare total RNA. For microarray experiment, 100 ng of RNA were finally converted to fluorescent cRNA, which was followed by hybridization, feature scanning and data analysis. Three replicates were tested for OD 0.3 and 1.4 whereas two replicates were used for OD 5.