Open AccessOnline monitoring of the respiratory quotient reveals metabolic phases during microaerobic 2,3‐butanediol production with Bacillus licheniformis
Author(s) -
Heyman Benedikt,
Tulke Hannah,
Putri Sastia Prama,
Fukusaki Eiichiro,
Büchs Jochen
Publication year - 2020
Publication title -
engineering in life sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.547
H-Index - 57
eISSN - 1618-2863
pISSN - 1618-0240
DOI - 10.1002/elsc.201900121
Subject(s) - respiratory quotient , bacillus licheniformis , 2,3 butanediol , oxygen , biology , mixed acid fermentation , biochemistry , food science , microbiology and biotechnology , fermentation , chemistry , bacteria , lactic acid , organic chemistry , genetics , bacillus subtilis , lactic acid fermentation
Microaerobic cultivation conditions are often beneficial for the biotechnological production of reduced metabolites like 2,3‐butanediol. However, due to oxygen limitation, process monitoring based on oxygen transfer rate, or dissolved oxygen measurement provides only limited information. In this study, online monitoring of the respiratory quotient is used to investigate the metabolic activity of Bacillus licheniformis DSM 8785 during mixed acid‐2,3‐butanediol production under microaerobic conditions. Thereby, the respiratory quotient provides valuable information about different metabolic phases. Based on partial reaction stoichiometries, the metabolic activity in each phase of the cultivation was revealed, explaining the course of the respiratory quotient. This provides profound information on the formation or consumption of glucose, 2,3‐butanediol, ethanol and lactate, both, in shake flasks and stirred tank reactor cultivations. Furthermore, the average respiratory quotient correlates with the oxygen availability during the cultivation. Carbon mass balancing revealed that this reflects the increased formation of reduced metabolites with increasing oxygen limitation. The results clearly demonstrate that the respiratory quotient is a valuable online signal to reveal and understand the metabolic activity during microaerobic cultivations. The approach of combining respiratory quotient monitoring with stoichiometric considerations can be applied to other organisms and processes to define suitable cultivation conditions to produce the desired product spectrum.