Johann Orlygsson
University of Akureyri
Title: Amino acid catabolism of Thermoanaerobacter and Caldanaerobacter species
Biography
Biography: Johann Orlygsson
Abstract
Thermoanaerobacter strains have been widely investigated for biofuel production from carbohydrates while proteins and
amino acids catabolism have received less attention. Amino acid catabolism is challenging under anaerobic conditions unless
hydrogen is removed. Recent reports have demonstrated that Th ermoanaerobacter strains can degrade branched-chain amino
acids (BCAAs) to a mixture of their corresponding fatty acids (BCFAs) and alcohols (BCOHs) when thiosulfate is present. Th e
aim of the presented work to evaluate the ability of these genera to degrade amino acids and better understand the mechanisms
dictating the observed end productratios. Th e type species of thegenera of Th ermoanaerobacter and Caldanaerobacter, were
investigated in batch culture for each of the proteogenic amino acids with and without the addition of thiosulfate as an electron
acceptor. Some strains in the genus could utilize serine and threonine without the addition of thiosulfate with acetate and
ethanol being the dominate products while BCFA/BCOH ratios from BCAA were highly dependent on species and substrate
when thiosulfate was added. BCAA catabolism resulted mixtures of the corresponding BCOH (0.5-5 mM) and BCFA (3.5-
15.5 mM) with partial substrate utilization being observed in some cases. Altering the liquid-gas phase ratio had an impact
on end product ratios; in the case of C. subterraneus subsp. yonseiensis, increasing the L-G ratio from 1.00 to 5.88, the BCOH
formation increased more than 5-fold (with thiosulfate) and less BCFA were produced.