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The search for more productive mammalian cell culture techniques has been primarily driven by the need to increase both the cell density and product concentration. In the technique used in our laboratory, microencapsulation, hybridoma cells were grown and monoclonal antibody was entrapped within microcapsules, which had a controlled membrane molecular weight cutoff. In our studies it was shown that using the alginate‐poly‐l‐lysine (PLL) microcapsule system and protein diffusion experiments, the capsule membrane molecular weight cutoff could be controlled from 20 × 103 to 300 × 103. This was achieved by increasing the viscosity average molecular weight (Mv) of the LL, used in the encapsulation procedure, from 14 × 103 to 525 × 103 and by decreasing the alginate — PLL reaction time from 40 minutes to 6 minutes. Cell culture studies with microencapsulated mouse hybridoma cells indicated that while the conventional (single‐membrane) microcapsules produced a maximum intracapsular cell density of about 2 × 107 cells/mL and a monoclonal antibody concentration of 1250 μg/mL, a modified (multiple‐membrane) capsule resulted in intracapsular cell densities of about 6 × 107 cells/mL and monoclonal antibody concentrations of 5300 μg/mL. These significant improvements in cell density and monoclonal antibody concentration were attributed to a lower (22%) intracapsular alginate content as well as better retention of the cell product by the modified capsule membrane.

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The rose-like aroma compound 2-phenylethanol (2-PE) is an important fragrance and flavor ingredient. Several yeast strains are able to convert l-phenylalanine (l-phe) to 2-PE among which Kluyveromyces marxianus has shown promising results. The limitation of this process is the low product concentration and productivity primarily due to end product inhibition. This study explored the possibility and benefits of using a solid-liquid Two-Phase Partition Bioreactor (TPPB) system as an in situ product removal technique. The system applies polymer beads as the sequestering immiscible phase to partition 2-PE and reduce the aqueous 2-PE concentration to non-inhibitory levels. Among six polymers screened for extracting 2-PE, Hytrel 8206 performed best with a partition coefficient of 79. The desired product stored in the polymer was ultimately extracted using methanol. A 3 L working volume solid-liquid batch mode TPPB using 500 g Hytrel as the sequestering phase generated a final overall 2-PE concentration of 13.7 g/L, the highest reported in the current literature. This was based on a polymer phase concentration of 88.74 g/L and aqueous phase concentration of 1.2 g/L. Even better results were achieved via contact with more polymers (approximately 900 g) with the aqueous phase applying a semi-continuous reactor configuration. In this system, a final 2-PE concentration (overall) of 20.4 g/L was achieved with 1.4 g/L in the aqueous and 97 g/L in the polymer phase. The overall productivities of these two reactor systems were 0.38 and 0.43 g/L h, respectively. This is the first report in the literature of the use of a polymer sequestering phase to enhance the bioproduction of 2-PE, and exceeds the performance of two-liquid phase systems in terms of productivity as well as ease of operation (no emulsions) and ultimate product recovery.