Jon Hansen

Development of a docosahexaenoic acid production technology using Schizochytrium: historical perspective and update.

Publisher Summary The fish oils contain both Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA). The research showed that DHA was important in infant nutrition, had positive effects on blood lipids and cardiovascular health in adults, was more effectively retained in the human body, and could be readily retroconverted to EPA. These and other factors suggested that DHA might be a better form of omega-3 Long-Chain Polyunsaturated Fatty Acid (LCPUFA) to function as a food ingredient or nutritional supplement for consumers. A bio-rational approach was used to develop a production technology for long-chain omega-3 fatty acids. This innovative collection/isolation/screening program resulted in the isolation of strains of a unique group of microorganisms, thraustochytrids, with significant biotechnological potential. Scale-up of this technology, using a strain of Schizochytrium sp ., resulted in a fermentation technology with the highest cell concentrations, highest unsaturated lipid productivities, and highest cellular concentrations of DHA ever reported for a microbial production technology.

The Sensitivity of the Dinoflagellate Crypthecodinium cohnii to Transient Hydrodynamic Forces and Cell-Bubble Interactions

The increased interest in the benefits of omega‐3 fatty acids for human health has resulted in the commercial development of the dinoflagellate Crypthecodinium cohnii for production of docosahexaenoic acid (DHA). The growing market demand for DHA requires highly efficient, very large scale cultures of DHA. While the effects of hydrodynamic forces on dinoflagellates have been investigated for several decades, the majority of the work focused on the negative effects of oceanic turbulence on the population growth of environmentally important dinoflagellates. In contrast, significantly less is known on the effect of hydrodynamic forces encountered by algae in bioprocesses. Unlike other studies conducted on algae, this study employed a microfluidic, flow contraction device to evaluate the effect of transient hydrodynamic forces on C. cohnii cells. It was found that C. cohnii cells can sustain the energy dissipation rate of 5.8 × 107 W/m3 without lysis. However, an obvious sublethal effect, the loss of flagella, was observed at a lower level of 1.6 × 107 W/m3. Finally the cell‐bubble interaction and the effect of bubble rupture were also explored to simulate the conditions of sparged bioreactors.

Growth inhibition of dinoflagellate algae in shake flasks: Not due to shear this time!

Large scale algae cultures present interesting challenges in that they exhibit characteristics of typical bacterial and animal cell cultures. One current commercial food additive, docosahexaenoic acid (DHA), is produced using the dinoflagellate algae, Crypthecodinium cohnii. Like animal cell culture, the perceived sensitivity of algae culture to hydrodynamic forces has potentially limited the agitation and aeration applied to these systems. However, the high density cultivation of C. cohnii required for an economically feasible process inevitably results in high oxygen demand. In this study, we demonstrated what first appeared to be a problem with shear sensitivity in shake flasks is most probably a mass transfer limitation. We subsequently demonstrated the limit of chronic and rapid energy dissipation rate, EDR, that C. cohnii cells can experience. This limit was determined using a microfluidic device connected in a recirculation loop to a stirred tank bioreactor, which has been previously used to repeatedly expose animal cells to high levels of EDR. Inhibition of cell growth was observed when C. cohnii cells were subjected to an EDR of 5.9 × 106 W/m3 with an average frequency of 0.2/min or more. This level of EDR is sufficiently high that C. cohnii can withstand typically encountered hydrodynamic forces in bioprocesses. This result suggests that at least one dinoflagellate algae, C. cohnii, is quite robust with respect to hydrodynamic forces and the scale‐up of process using this type of algae should be more concerned with providing sufficient gas transfer given the relatively high oxygen demand.