As a reaction to decreasing fossil feedstock, the biotechnological production of fine chemicals has gained an increased academic and industrial interest over the last decades. Within this development biphasic whole-cell biotransformations have been shown to be reliable and efficient alternatives to common chemical synthesis routes, especially for the production of e.g. apolar enantiopure organic compounds. Biphasic whole-cell biotransformations provide high stereo selectivity as well as high product titers due to the presence of an organic phase serving as substrate reservoir and product sink. The organic phase thereby minimizes the toxification of the biocatalyst by the substrate and/or product. The main bottleneck for an industrial implementation is the formation of stable Pickering type emulsions due to the presence of whole cells. State of the art downstream processing of these emulsions includes the use of excessive centrifugation, chemical de-emulsifiers or thermal stress, leading to inefficient processes. In contrast, using the catastrophic phase inversion phenomenon applied within this work, which describes a sudden switch of emulsion type caused by addition of dispersed phase, Pickering type emulsions can be destabilized efficiently in a continuous setup. Four different reaction systems (bis(2-ethylhexyl) phthalate, ethyl oleate or dodecanol as organic phase in combination with E.coli JM101 or Pseudomonas putida VLB120) 2 were successfully separated.
Based on batch experiments to determine the influence of phase ratio and processing conditions, a simple prototype, consisting of a single mixer settler stage, capable of continuous emulsion separation was developed and constructed. In contrast to state of the art centrifugal separations, ACPI benefits from its simple setup as well as low operating costs and is therefore a simple applicable method that can generally be used for separation of stable Pickering type emulsions based on the knowledge of the point of inversion. This fact qualifies ACPI as a considerable alternative as first separation step in the DSP of biphasic whole-cell biotransformations.