Branched-chain amino acid catabolism of Thermoanaerobacter strain AK85 and the influence of culture conditions on branched-chain alcohol formation

• Published in: Amino acids 2019-07, Vol.51 (7), p.1039-1054
• Main Authors: Scully, Sean Michael, Orlygsson, Johann
• Format: Article
• Language: English
• Subjects: Alcohol; Alcohols; Alcohols - metabolism; Amino acids; Amino Acids - metabolism; Analytical Chemistry; Biochemical Engineering; Biochemistry; Biomedical and Life Sciences; Bioprocessing; Catabolism; Chain branching; Chains; Culture; Fatty acids; Fatty Acids - metabolism; Fermentation; Glucose metabolism; Hydrogen-Ion Concentration; Isoleucine; Isoleucine - metabolism; Kinetics; Leucine; Leucine - metabolism; Life Sciences; Metabolism; Neurobiology; Original Article; Proteomics; Thermoanaerobacter - metabolism; Thiosulfate; Thiosulfates; Thiosulfates - chemistry
• ISSN: 0939-4451; 1438-2199
• DOI: 10.1007/s00726-019-02744-z

The bioprocessing of amino acids to branched-chain fatty acids and alcohols is described using Thermoanaerobacter strain AK85. The amino acid utilization profile was evaluated without an electron scavenger, with thiosulfate, and in a co-culture with a methanogen. There was an emphasis on the production of branched-chain alcohols and fatty acids from the branched-chain amino acids, particularly the influence of culture conditions which was investigated using isoleucine, which revealed that the concentration of thiosulfate was of great importance for the branched-chain alcohols/fatty acid ratio produced. Kinetic studies show that branched-chain amino acid fermentation is relatively slow as compared to glucose metabolism with the concentrations of the branched-chain alcohol increasing over time. To understand the flow of electrons and to investigate if the branched-chain fatty acid was being converted to branched-chain alcohol, enzyme assays and fermentation studies using 13 C-labeled leucine and 3-methyl-1-butyrate were performed which indeed suggest that carboxylic acid reduction is a source of branched-chain alcohols when Thermoanaerobacter strain AK85 was cultivated with thiosulfate as an electron scavenger.