Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The market for all-natural food products has shifted the interest of manufacturing methods for flavor additives away from conventional chemical synthesis and towards bioconversion. Bioconversion of alcohols to aldehydes utilizing the AOX enzyme of the methylotrophic yeast Pichia pastoris is one way to enable production of natural flavors of commercial importance. Methanol induced P. pastoris cells are able to generate energy from the controlled oxidation of methanol to formaldehyde by producing large amounts of active AOX. Although the cell can only utilize methanol for energy, AOX is able to perform controlled oxidation of the alcohol group of any short chain (1-8 carbons) aliphatic alcohol converting it to the corresponding aldehyde. In this study, the practical application of this bioconversion was examined for the generation of n-butyraldehyde from butanol. As with similar aldehydes, n-butyraldehyde has practical use as a flavor additive by imparting a butter sensorial quality to food and it can be ethyl and methylated into a diverse array of complex flavor compounds. Two main issues effect the practical application of utilizing whole-cell P. pastoris for bioconversion to n-butyraldehyde: product inhibition and recovery of the volatile aldehyde. In this work, we examined product inhibition by performing comparative bioconversions with two different buffering systems, a typical pH buffer of potassium phosphate and the other a tris-borate chelating system. With regard to product recovery, a comparison was performed between an air-sparged cold trap and a closed-pressurized reactor design. A detailed description of the bioconversion and the product recovery will be presented.