Comprehensive analysis of metabolic sensitivity of 1,4‐butanediol producing Escherichia coli toward substrate and oxygen availability

Abstract

Nowadays, chemical production of 1,4-butanediol is supplemented by biotechnological processes using a genetically modified Escherichia coli strain, which is an industrial showcase of successful application of metabolic engineering. However, large scale bioprocess performance can be affected by presence of physical and chemical gradients in bioreactors which are a consequence of imperfect mixing and limited oxygen transfer. Hence, upscaling comes along with local and time dependent fluctuations of cultivation conditions. This study emphasizes on scale-up related effects of microbial 1,4-butanediol production by comprehensive bioprocess characterization in lab scale. Due to metabolic network constraints 1,4-butanediol formation takes place under oxygen limited microaerobic conditions, which can be hardly realized in large scale bioreactor. The purpose of this study was to assess the extent to which substrate and oxygen availability influence the productivity. It was found, that the substrate specific product yield and the production rate are higher under substrate excess than under substrate limitation. Furthermore, the level of oxygen supply within microaerobic conditions revealed strong effects on product and by-product formation. Under strong oxygen deprivation nearly 30% of the consumed carbon is converted into 1,4-butanediol, whereas an increase in oxygen supply results in 1,4-butanediol reduction of 77%. Strikingly, increasing oxygen availability leads to strong increase of main by-product acetate as well as doubled carbon dioxide formation.The study provides clear evidence that scale-up of microaerobic bioprocesses constitute a substantial challenge. Although oxygen is strictly required for product formation, the data give clear evidence that terms of anaerobic and especially aerobic conditions strongly interfere with 1,4-butanediol production.

Recent Advances in Sustainable Plastic Upcycling and Biopolymers

“…For example, succinic acid and 1,4‐BDO, both of which are used for the synthesis of PBS as monomers, have successfully been produced by employing metabolically engineered microorganisms in significant yields suitable for commercial production (Table 1 and Figure 2). [ 57–74 ] In particular, the production of succinic acid is currently being replaced by biological production and several companies already produce bio‐succinic acid in an industrial scale. [ 94,100 ] Similar to PBS, all monomers of PBAT, such as 1,4‐BDO, adipic acid, and even TPA, can also be produced by engineered microbial strains (Table 1 and Figure 2).…”

“…[ 94,100 ] Similar to PBS, all monomers of PBAT, such as 1,4‐BDO, adipic acid, and even TPA, can also be produced by engineered microbial strains (Table 1 and Figure 2). [ 71–80 ] In this respect, both PBAT and PBS can also be regarded as biodegradable biopolymers, which was originally thought for only PLA.…”

Practical genetic control strategies for industrial bioprocesses

“…Amyris has used a maltose switch-based system with multilevel control using yeast in commercial scale fermentation processes (Chua et al, 2019 ). Additionally, non-genetic metabolic control strategies providing separation of growth and production phases and strain stability have been successfully applied to improve industrial fermentation processes (Pooth et al, 2020 ; Sandoval et al, 2014 ).…”