Biomass Depolymerization projects

Diversity and Physiology of Solventogenic Clostridia

We propose to study the Acetone-Butanol-Ethanol (ABE) fermentation in a diverse set of strains obtained from culture collections as well as industrial strains of solventogenic Clostridia: 1) Obtain a wide selection of existing strains from culture collections that are representative type strains or have been used for industrial fermentations. We intend to build a large collection of strains representing the four main species groups. 2) Obtain a newly isolated set of environmental cultures and strains that are capable of solvent production at mesophilic and thermophilic temperatures. We will supplement the extant strains above by bringing into culture a fresh set of isolates of solventogenic Clostridia with the emphasis on thermophilic bacteria capable of producing alcohols and solvents using enrichments and other standard anaerobic laboratory techniques. 3) Screen the above collections for substrate range, diversity of solvent ratios, yields and titres, phage typing as well as genetic tractability to generate a versatile and adaptable set of isolates for future industrial application. The evaluation of the genetic transformability parameters of strains used in the ABE fermentation such as cell viability, transformation efficiency and frequency of transformation are essential steps to identifying which strains are the most adequate for breeding programs and which strains are best suited for genetic and metabolic engineering approaches to enhancing the ABE fermentation.

project Highlights

2014 Highlights

Our objectives are to obtain a wide selection of existing strains from culture collections that are representative type strains or have been used for industrial fermentations. A parallel objective is to obtain a newly isolated set of environmental cultures and strains that are capable of solvent production at mesophilic and thermophilic temperatures. We have obtained 76 accessions of solventogenic Clostridia from NRRL, DSMZ, NCIMB and JCM culture collections. In addition, we have obtained 13 strains of spore forming bacteria for the soil sample collected from the Enterprise Refinery in Louisiana. Several of these have potential in biofuel applications. Screening of the strain accessions for solvent titers and ratios in medium containing sugarcane juice as energy source is in progress. Based on initial fermentation performance, we selected 10 strains for genome sequencing. These genomes have been assembled and analyzed for CRISPR organization and structure and demonstrate a consistent presence as well as considerable diversity.

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