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. 2022 Mar 16;9(3):122.
doi: 10.3390/bioengineering9030122.

Cell Retention as a Viable Strategy for PHA Production from Diluted VFAs with Bacillus megaterium

Milos Kacanski  1 , Lukas Pucher  1 , Carlota Peral  2 , Thomas Dietrich  2 , Markus Neureiter  1
Affiliations

Cell Retention as a Viable Strategy for PHA Production from Diluted VFAs with Bacillus megaterium

Milos Kacanski et al. Bioengineering (Basel). .

Abstract

The production of biodegradable and biocompatible materials such as polyhydroxyalkanoates (PHAs) from waste-derived volatile fatty acids (VFAs) is a promising approach towards implementing a circular bioeconomy. However, VFA solutions obtained via acidification of organic wastes are usually too diluted for direct use in standard batch or fed-batch processes. To overcome these constraints, this study introduces a cell recycle fed-batch system using Bacillus megaterium uyuni S29 for poly(3-hydroxybutyrate) (P3HB) production from acetic acid. The concentrations of dry cell weight (DCW), P3HB, acetate, as well as nitrogen as the limiting substrate component, were monitored during the process. The produced polymer was characterized in terms of molecular weight and thermal properties after extraction with hypochlorite. The results show that an indirect pH-stat feeding regime successfully kept the strain fed without prompting inhibition, resulting in a dry cell weight concentration of up to 19.05 g/L containing 70.21% PHA. After appropriate adaptations the presented process could contribute to an efficient and sustainable production of biopolymers.

Keywords: Bacillus megaterium; cell retention; poly(3-hydroxybutyrate); polyhydroxyalkanoates; volatile fatty acids.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the study’s design, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Schematic representation of the cell recycle system. Addition of acid (grey) and VFA feed (orange) and removal of permeate (green) via pumps is recorded by scales and controlled by the process control system in order to keep process values stable and maintain a constant volume in the reactor.
Figure 2
Figure 2
Cultivation of Bacillus megaterium uyuni S29 in a cell recycle process (I). Biomass (as DCW) and polymer (P3HB) concentration (left axis) and concentration of acetic acid and nitrogen (as TKN) (right axis). Error bars represent standard deviation from triplicate samples.
Figure 3
Figure 3
Cultivation of Bacillus megaterium uyuni S29 in a cell recycle process (II, replicate). Biomass (as DCW) and polymer (P3HB) concentration (left axis) and concentration of acetic acid and nitrogen (as TKN) (right axis). Error bars represent standard deviation from triplicate samples.
Figure 4
Figure 4
Transmembrane pressure of the two cell recycle processes with Bacillus megaterium uyuni S29. The membrane pressure curves are shown as 60 min rolling averages.
See this image and copyright information in PMC

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