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Thermodynamic analysis of growth of Methanobacterium thermoautotrophicum
Author(s) -
Schill Natascha A.,
Liu JingSong,
Stockar Urs von
Publication year - 1999
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19990705)64:1<74::aid-bit8>3.0.co;2-3
Subject(s) - gibbs free energy , thermodynamics , methanogenesis , chemistry , entropy production , yield (engineering) , catabolism , biomass (ecology) , growth rate , energy balance , enthalpy , entropy (arrow of time) , metabolism , biochemistry , biology , methane , ecology , organic chemistry , physics , geometry , mathematics
Growth of Methanobacterium thermoautotrophicum, an anaerobic archaebacterium using methanogenesis as the catabolic pathway, is characterized by large heat production rates, up to 13 W g −1 , and low biomass yields, in the order of 0.02 C‐mol mol −1 H 2 consumed. These values, indicating a possibly “inefficient” growth mechanism, warrant a thermodynamic analysis to obtain a better understanding of the growth process. The growth‐associated heat production (Δ r H X 0,min ) and the growth‐associated Gibbs energy dissipation per mol biomass formed (Δ r G X min ) were −3730 kJ C‐mol −1 and −802 kJ C‐mol −1 , respectively. The Gibbs energy change found in this study is indeed unusually high as compared to aerobic methylotrophes, but not untypical for methanogens grown on CO 2 . It explains the low biomass yield. Based on the information available on the energetic metabolism and on an ATP balance, the biomass yield can be predicted to be approximately in the range of the experimentally determined value. The fact that the exothermicity exceeds vastly even the Gibbs energy change can be explained by a dramatic entropy decrease of the catabolic reaction. Microbial growth characterized by entropy reduction and correspondingly by unusually large heat production may be called entropy‐retarded growth. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 74–81, 1999.