Knothe Gerhard

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Knothe
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Gerhard
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  • Preprint
    Decolorization improves the fuel properties of algal biodiesel from Isochrysis sp.
    ( 2016-03) O’Neil, Gregory W. ; Knothe, Gerhard ; Williams, John R. ; Burlow, Noah P. ; Reddy, Christopher M.
    Results from the comprehensive fuel testing according to American Society for Testing and Materials International (ASTM) standards of an alkenone-free and decolorized biodiesel produced from the industrially grown marine microalgae Isochrysis sp. are presented. Fatty acid methyl ester (FAME) profiles of the non-decolorized and subsequently decolorized biodiesel fuels were nearly identical, yet the fuel properties were remarkably different. Significant positive impacts on the cetane number, kinematic viscosity, and lubricity were observed, indicating a potential deleterious effect of pigments like chlorophylls and pheophytins on these fuel properties. The decolorization process using montmorillonite K10 gave on average 90% mass recovery, and allowed for an otherwise unobtainable cloud point determination. Oxidative stability of the decolorized Isochrysis biodiesel remained well below the minimum prescribed in biodiesel standards due to elevated content of highly polyunsaturated fatty acids, however other values were in the range of those prescribed in the ASTM standards. Overall, decolorization improved the fuel properties of biodiesel from Isochrysis and may provide a path toward improved biodiesel fuels from other algal species.
  • Article
    Experimental protocol for biodiesel production with isolation of alkenones as coproducts from commercial Isochrysis algal biomass
    (JoVE, 2016-06-24) O’Neil, Gregory W. ; Williams, John R. ; Wilson-Peltier, Julia ; Knothe, Gerhard ; Reddy, Christopher M.
    The need to replace petroleum fuels with alternatives from renewable and more environmentally sustainable sources is of growing importance. Biomass-derived biofuels have gained considerable attention in this regard, however first generation biofuels from edible crops like corn ethanol or soybean biodiesel have generally fallen out of favor. There is thus great interest in the development of methods for the production of liquid fuels from domestic and superior non-edible sources. Here we describe a detailed procedure for the production of a purified biodiesel from the marine microalgae Isochrysis. Additionally, a unique suite of lipids known as polyunsaturated long-chain alkenones are isolated in parallel as potentially valuable coproducts to offset the cost of biodiesel production. Multi-kilogram quantities of Isochrysis are purchased from two commercial sources, one as a wet paste (80% water) that is first dried prior to processing, and the other a dry milled powder (95% dry). Lipids are extracted with hexanes in a Soxhlet apparatus to produce an algal oil ("hexane algal oil") containing both traditional fats (i.e., triglycerides, 46-60% w/w) and alkenones (16-25% w/w). Saponification of the triglycerides in the algal oil allows for separation of the resulting free fatty acids (FFAs) from alkenone-containing neutral lipids. FFAs are then converted to biodiesel (i.e., fatty acid methyl esters, FAMEs) by acid-catalyzed esterification while alkenones are isolated and purified from the neutral lipids by crystallization. We demonstrate that biodiesel from both commercial Isochrysis biomasses have similar but not identical FAME profiles, characterized by elevated polyunsaturated fatty acid contents (approximately 40% w/w). Yields of biodiesel were consistently higher when starting from the Isochrysis wet paste (12% w/w vs. 7% w/w), which can be traced to lower amounts of hexane algal oil obtained from the powdered Isochrysis product.