Caloramator Boliviensis, a New Thermoanaerobe with Interesting Metabolic Properties
Abstract: A novel ethanol-producing thermoanaerobe Caloramator boliviensis 45BT (=DSM 22065T, =CCUG 57396T) was isolated from a hot spring of the Bolivian highlands. C. boliviensis possesses the ability to utilize a wide range of substrates and can efficiently convert hexoses and pentoses into ethanol with concomitant production of acetate, carbon dioxide and hydrogen as by-products of fermentation. However, under different cultivation conditions C. boliviensis yields lactate, butyrate, propanediol, succinate and formate. A branched metabolism and an interesting catabolic flexibility are characteristics of C. boliviensis. An usual mixed acid fermentation could be directed to a glucose-based acetogenic, homolactic or homoethanolic metabolism. In addition, redistribution of end-products led to a lactate-based butyrate formation described for the first time for a member of the Caloramator genus. The flexibility to switch between metabolic pathways in order to balance the electron and carbon flow makes C. boliviensis an interesting candidate for metabolic engineering to maximize ethanol productivity. Based on the interesting characteristics described above, the fermentative metabolism of C. boliviensis was also evaluated at genome level. The draft genome of C. boliviensis (3.2 Mb, G+C 32 mole%) encompasses 2896 predicted protein-coding genes, the larger number of genes match to the transport and metabolism of amino acids and carbohydrates. Although, C. boliviensis displays potential for producing ethanol, before developing a full process, limitations such as substrate and product concentrations, nutrients requirement, reaction rates and metabolic shifts must be overcome. Nevertheless, the genome functional annotation provides a platform for future metabolic engineering strategies to improve ethanol titres and productivities and to increase the understanding of the physiology of C. boliviensis.
This dissertation MIGHT be available in PDF-format. Check this page to see if it is available for download.