(235e) Scale-Up of Fermentation Process for Production of Bisabolene, a Novel Advanced Biofuel Precursor
Production of advanced biofuels and precursors through engineering of biochemical pathways is a promising approach to generate advanced, sustainable biofuels. Researchers at the Joint BioEnergy Institute (JBEI) have identified a novel biosynthetic alternative to D2 diesel fuel, bisabolane, and engineered Saccharomyces cerevisiaefor the production of its immediate precursor, bisabolene. In collaboration with JBEI, the Advanced Biofuels Process Demonstration Unit (ABPDU) has demonstrated this technology at 2, 15, and 300 L scale. A fed batch fermentation was conducted, in which, a constant feed of 500 g/L glucose feed medium is triggered by a rise in dissolved oxygen (DO). A decane overlay of 10% (v/v) was used to continuously extract bisabolene from the fermentation broth thus avoiding product inhibition and facilitating recovery. After completion of the fed batch, bisabolene concentrations of 3.5 g/L were observed in 2 L reactors, notably higher than results observed in previous lab scale research. An internal standard, heptadecane, was utilized to investigate evaporative losses of decane and mass balance of the process. Several scale-up related process issues, critical for the commercialization of this technology, were investigated in this study, including: (i) adequate mixing to create an emulsion of the fermentation broth and decane, (ii) optimal glucose feed rates, (iii) mitigation of evaporative losses of decane and product, and (iv) controlled aeration and agitation based on DO. Many laboratory scale technologies developed in batch reactors may or may not be relevant in commercial context due to scale-up issues. At the ABPDU, we investigate and resolve such scale-up related process issues for several unit operations involved in biomass conversion to biofuels. In this study, we developed commercially relevant fed-batch fermentation process for bisabolene and, as a first, demonstrated its production beyond lab scale.
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