Continuous Ethanol Fermentation and Recovery Using an Improved Zeolite Membrane Bioreactor

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PI: Nielsen, David Institution: Arizona State University Proposal Number: 1067684Title: Continuous Ethanol Fermentation and Recovery using an ImprovedZeolite Membrane BioreactorThis research aims to develop a lab-scale bioprocess which integrates fermentation with zeolite membrane pervaporation for the high-rate, high-purity, and continuous production of biofuel ethanol. To support this objective, the research is composed of three principal aims: 1) the synthesis and development of improved, aluminum-free hydrophobic zeolite membranes with both elevated ethanol permselectivity and flux, 2) characterization of non-ideal physical/biological phenomena occurring at the membrane surface, and 3) the design, development, and characterization of novel bioprocesses incorporating zeolite membrane pervaporation as a means of economical, in situ product recovery.Intellectual Merit: The first principal aim focuses on the synthesis of high quality, aluminum-free silicalite membranes on chemically inert porous zirconia supports. These new membranes, which will be fabricated in both disk and tubular geometries, are expected to demonstrate much higher fluxes and ethanol/water selectivity than existing polymer and zeolite membranes. The second important aim is to provide fundamental insights into the mechanistic nature of non-ideal, physical and/or biological interactions occurring upon zeolite surfaces, as well as their resultant effect on membrane properties and impact on separation performance. These studies will help to develop a mechanistic understanding of biofouling (by both proteins and whole cells) as a function of relevant process conditions and biocatalyst genotype. The final aim is to design, develop, and characterize a scalable and integrated bioprocess for the continuous production and recovery of ethanol from yeast fermentations using zeolite membrane pervaporation. To support sustained and high-level performance, operating policies and fouling reduction strategies, to include in situ regeneration by membrane backflushing, will be developed and optimized.Broader Impact: This study will enable developments in separation science and bioprocess design, supporting the development of sustainable biofuels. The concept of aluminum-free, silicalite membrane preparation can ultimately be translated to the synthesis of other zeolite membranes to enable greater material compatibility and higher performance for other separation applications. Newly synthesized tubular zeolite membranes and their synthesis protocols could find other applications for separation of gas and liquid mixtures of industrial importance, such as refinery gas of hydrocarbon/hydrogen and other alcohol/water mixtures. The development of a bioprocess enabling the selective separation of inhibitory products by zeolite membrane pervaporation could have broader applications for the production of additional biochemicals and emerging, next generation biofuels. The characterization of physical/biological interactions at zeolite surfaces could be valuable for assessing the future prospects of zeolite materials in fields ranging from bioenergy production to biomedical engineering. The recruited personnel and dual-use equipment resources made possible through this study will enable the development of biologically-based laboratory modules to enrich the educational experiences of undergraduates.