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. 2016 Mar;6(1):11.
doi: 10.1186/s13568-016-0183-2. Epub 2016 Feb 9.

Integrated foam fractionation for heterologous rhamnolipid production with recombinant Pseudomonas putida in a bioreactor

Janina Beuker  1 , Anke Steier  1 , Andreas Wittgens  2 , Frank Rosenau  2 , Marius Henkel  3 , Rudolf Hausmann  1
Affiliations

Integrated foam fractionation for heterologous rhamnolipid production with recombinant Pseudomonas putida in a bioreactor

Janina Beuker et al. AMB Express. 2016 Mar.

Abstract

Heterologeous production of rhamnolipids in Pseudomonas putida is characterized by advantages of a non-pathogenic host and avoidance of the native quorum sensing regulation in Pseudomonas aeruginosa. Yet, downstream processing is a major problem in rhamnolipid production and increases in complexity at low rhamnolipid titers and when using chemical foam control. This leaves the necessity of a simple concentrating and purification method. Foam fractionation is an elegant method for in situ product removal when producing microbial surfactants. However, up to now in situ foam fractionation is nearly exclusively reported for the production of surfactin with Bacillus subtilis. So far no cultivation integrated foam fractionation process for rhamnolipid production has been reported. This is probably due to excessive bacterial foam enrichment in that system. In this article a simple integrated foam fractionation process is reported for heterologous rhamnolipid production in a bioreactor with easily manageable bacterial foam enrichments. Rhamnolipids were highly concentrated in the foam during the cultivation process with enrichment factors up to 200. The described process was evaluated at different pH, media compositions and temperatures. Foam fractionation processes were characterized by calculating procedural parameter including rhamnolipid and bacterial enrichment, rhamnolipid recovery, YX/S, YP/X, and specific as well as volumetric productivities. Comparing foam fractionation parameters of the rhamnolipid process with the surfactin process a high effectiveness of the integrated foam fractionation for rhamnolipid production was demonstrated.

Keywords: Biosurfactant; Downstream processing; Foam fractionation; Heterologous rhamnolipid; In situ product removal (ISPR); Pseudomonas putida.

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Figures

Fig. 1
Fig. 1
Setup for integrated foam fractionation in a bioreactor. Foam is generated during cultivation process in the bioreactor and channeled through the off gas cooler into cooled exchangeable foam bags
Fig. 2
Fig. 2
Time course of overall biomass, glucose and rhamnolipid masses (sum of bioreactor and integral foam fractions) during foam fractionation process. a shows results of bioreactor cultivations using Wilms medium setup, b shows results of bioreactor cultivations using ModR medium setup. The values for biomass (black circles), glucose (grey triangles) and rhamnolipid (blank squares) are given as mean values of two bioreactor cultivations. Dotted, solid black and solid grey lines represent the logistic fit functions of the rhamnolipid, biomass and glucose time course, respectively based on Eq. 1
Fig. 3
Fig. 3
Time course of differential bacterial and rhamnolipid enrichment and integral rhamnolipid recovery during foam fractionation process. a shows rhamnolipid (blank) and bacterial (black) enrichments using Wilms (triangles) and ModR (squares) medium setup referring to a logarithmic axis. The values for rhamnolipid and bacterial enrichment were calculated as depicted in Eq. 6, b shows rhamnolipid recovery using Wilms (triangles) and ModR (squares) medium setup calculated according to Eq. 7
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