Browsing by Author "Ankenbauer, Andreas"

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Open Access
Micro‐aerobic production of isobutanol with engineered Pseudomonas putida
(2021) Ankenbauer, Andreas; Nitschel, Robert; Teleki, Attila; Müller, Tobias; Favilli, Lorenzo; Blombach, Bastian; Takors, Ralf
Pseudomonas putida KT2440 is emerging as a promising microbial host for biotechnological industry due to its broad range of substrate affinity and resilience to physicochemical stresses. Its natural tolerance towards aromatics and solvents qualifies this versatile microbe as promising candidate to produce next generation biofuels such as isobutanol. In this study, we scaled‐up the production of isobutanol with P. putida from shake flask to fed‐batch cultivation in a 30 L bioreactor. The design of a two‐stage bioprocess with separated growth and production resulted in 3.35 gisobutanol L-1. Flux analysis revealed that the NADPH expensive formation of isobutanol exceeded the cellular catabolic supply of NADPH finally causing growth retardation. Concomitantly, the cell counteracted to the redox imbalance by increased formation of 2‐ketogluconic thereby providing electrons for the respiratory ATP generation. Thus, P. putida partially uncoupled ATP formation from the availability of NADH. The quantitative analysis of intracellular pyridine nucleotides NAD(P)+ and NAD(P)H revealed elevated catabolic and anabolic reducing power during aerobic production of isobutanol. Additionally, the installation of micro‐aerobic conditions during production doubled the integral glucose‐to‐isobutanol conversion yield to 60 mgisobutanol gglucose-1 while preventing undesired carbon loss as 2‐ketogluconic acid.
Open Access
Micro-aerobic production of isobutanol with Pseudomonas putida and investigation of its resilience to substrate limitations
(2022) Ankenbauer, Andreas; Takors, Ralf (Prof. Dr.-Ing.)
The transition from an economy based on fossil resources to a regenerative economy is imminent yet uncertain. Despite an awareness of the scarcity of fossil fuels and the increasing natural disasters due to climate change, the world’s renewable energy supply still constitutes less than 20% of the total energy supply. To reduce humankind’s carbon footprint, next-generation biofuels, such as ethanol or isobutanol, have the potential to revolutionize the transportation energy demand. These biofuels can be produced from renewable feedstock in large bioreactors using microorganisms. However, inhomogeneities, such as carbon or oxygen gradients in large-scale bioreactors, often limit the efficiency of such industrial bioprocesses. The soil bacterium Pseudomonas putida has the potential to supersede existing industrial workhorses like Escherichia coli or Corynebacterium glutamicum due to its natural tolerance towards alcohols, its versatile repertoire of stress responses, and its affinity to a broad range of substrates. This thesis aims to investigate the capability of isobutanol production in P. putida KT2440 and to explore its performance during large-scale stress.