Novel multiphase loop reactor with improved aeration prevents excessive foaming in Rhamnolipid production by Pseudomonas putida

Abstract

Rhamnolipids are biosurfactants that tend to cause strong foaming, making microbial production in an aerated stirred tank fermenter challenging. The continuous removal of rhamnolipids from the cultivation broth via in situ liquid-liquid extraction can remedy this foam challenge, and thereby supports long-term cultivation and production. However, for efficient processing and stable phase separation, a specialized apparatus is required. In this study, the novel multiphase loop reactor, which is a modified airlift reactor with an internal loop enabling continuous in situ liquid-liquid extraction, was designed and adapted to produce rhamnolipids with a recombinant bacterium, Pseudomonas putida KT2440. The initially designed multiphase loop reactor showed a low oxygen transfer rate, unable to meet the oxygen demand of the whole-cell biocatalyst, resulting in inefficient growth and production. A re-design of the sparger via 3D printing enabled a high oxygen supply allowing rhamnolipid production at key performance indicators that matched stirred-tank reactor cultivations. Advantageously, the multiphase loop reactor allowed stable and constant phase separation and solvent removal enabling continuous cultivation in the future. Concluding, the successful use of the multiphase loop reactor for rhamnolipid synthesis is presented, highlighting its potential to become a new platform technology for intensified bioprocessing.

Methyl ketones: a comprehensive study of a novel biofuel

“…Because there were no peaks in shear stress due to stirring, highly reduced emulsification occurred compared to the STRs. 38 Stable phase separation was achieved in the coalescing unit. From here, a coherent layer of the organic phase formed, which was then continuously recirculated.…”

“…For the details of the MPLR setup, refer to Campenhausen et al , 2023 and ESI file 3, Fig. A.1 † 38.…”

“…[33][34][35][36][37] Recently, a new bioreactor type, namely a multiphase loop reactor (MPLR, Fig. 1) was designed for the circumvention of cumbersome emulsion formation, 38 reducing the energy entry enormously, while compromising only little on extraction efficiency.…”

“…Under ideal conditions, as realized by the novel multiphase loop reactor, only decanting is required. 38,40,41 The resulting methyl ketone mixture was extensively evaluated for its suitability as a fuel in combustion engines based on a range of performance parameters, including ash point, viscosity, and lubrication behavior. Using this information, a surrogate mixture was assessed in terms of the combustion performance in a singlecylinder engine.…”

High-quality physiology of Alcanivorax borkumensis SK2 producing glycolipids enables efficient stirred-tank bioreactor cultivation

“…Various approaches can be employed to mitigate foam formation in fermentation processes, such as adding antifoaming agents or utilizing mechanical foam breakers. Alternative approaches to foam prevention include in situ liquid-liquid extraction ( Demling et al, 2020 ; von Campenhausen et al, 2023 ), foam fractionation ( Blesken et al, 2020 ; Koop et al, 2020 ; Oraby et al, 2023 ), defoamers as substrates ( Sha et al, 2012 ; Bator et al, 2020 ), pressurized headspace aeration ( Weiser et al, 2022 ), and bubble-free membrane aeration ( Bongartz et al, 2021 ; Bongartz et al, 2023 ).…”