P132: Screening Lactobacillus casei strains for attributes of relevance to the production of advance biofuels

Genetic diversity and evolution of L. casei strains have been examined utilizing multi-locus sequence typing, comparative genomic hybridization, and comparative genomic analysis. These approaches have resulted in the identification of the L. casei core and pan genomes, which contain 1675 and 7530 genes, respectively. L. casei genome size ranged from approximately 2.76 to 3.36 Mbp, hence the variable portion of the L. casei genome ranged from 33 to 50%.  Our goal was to screen L. casei for strain specific attributes of relevance to the production of advance biofuels from starch and lignocellulosic feedstocks.  L. casei strains were examined for their ability to ferment plant component derivatives. Only L. casei A2-362 was capable of utilizing xylose, while cellobiose was utilized by majority of the strains. L. casei strains examined exhibited high innate tolerance to ethanol, propanol, butanol, isobutanol and 2- methyl-1-butanol, with concentrations of 6.4, 3.3, 1.7, 1.8 and 0.7%, respectively, required to reduce the maximal growth rate by 50%. Diversity among L. casei strains has also been examined by comparison of draft metabolic models. The Model SEED platform was utilized to generate draft metabolic models for L. casei ATCC334 and 12A.These models have been modified by removing thermodynamically infeasible cycles and correcting metabolic reactions that were found to be elementally imbalanced. Predictions of the model for amino acid requirements have been validated against experimental growth phenotypes. These results suggest that a number of phenotypes relevant to the use of L. casei strains for the production of biofuels are strain-specific.