Meta-Analysis and Functional Validation of Nutritional Requirements of Solventogenic Clostridia Growing under Butanol Stress Conditions and Coutilization of d-Glucose and d-Xylose

Abstract

ABSTRACTRecent advances in systems biology, omics, and computational studies allow us to carry out data mining for improving biofuel production bioprocesses. Of particular interest are bioprocesses that center on microbial capabilities to biotransform both the hexose and pentose fractions present in crop residues. This called for a systematic exploration of the components of the media to obtain higher-density cultures and more-productive fermentation operations than are currently found. By using a meta-analysis approach of the transcriptional responses to butanol stress, we identified the nutritional requirements of solvent-tolerant strainClostridium beijerinckiiSA-1 (ATCC 35702). The nutritional requirements identified were later validated using the chemostat pulse-and-shift technique.C. beijerinckiiSA-1 was cultivated in a two-stage single-feed-stream continuous production system to test the proposed validated medium formulation, and the coutilization ofd-glucose andd-xylose was evaluated by taking advantage of the well-known ability of solventogenic clostridia to utilize a large variety of carbon sources such as mono-, oligo-, and polysaccharides containing pentose and hexose sugars. Our results indicated thatC. beijerinckiiSA-1 was able to coferment hexose/pentose sugar mixtures in the absence of a glucose repression effect. In addition, our analysis suggests that the solvent and acid resistance mechanisms found in this strain are differentially regulated compared to strain NRRL B-527 and are outlined as the basis of the analysis toward optimizing butanol production.