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    Hemolysis as a Rapid Screening Technique for Assessing the Toxicity of Native Surfactin and a Genetically Engineered Derivative
    (WILEY, 2017) Colonna, William J.; Marti, Mustafa E.; Nyman, John A.; Green, Chris; Glatz, Charles E.
    If biosurfactants are to achieve their promise in environmental oil-spill remediation, their toxicity to marine life must be assessed. A killifish larvae assay is commonly used as a measure of toxicity but is difficult and nonlinear in response. Red blood cell (RBC) hemolysis has also been the basis for assays of some surfactant levels. Here we present a modified sheep RBC suspension assay and compare its response to that of the fish assay for surfactin and its genetically modified variant fatty-acyl-glutamate (FA-Glu). This is the first report of hemolytic activity as a property of FA-Glu. The method's potential for screening for toxicity against marine organisms is demonstrated. (C) 2016 American Institute of Chemical Engineers Environ Prog, 36: 505-510, 2017
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    Production of fatty-acyl-glutamate biosurfactant by Bacillus subtilis on soybean co-products
    (ELSEVIER SCIENCE BV, 2015) Marti, Mustafa E.; Colonna, William J.; Reznik, Gabriel; Pynn, Michelle; Jarrell, Kevin; Lamsal, Buddhi; Glatz, Charles E.
    Fatty-acyl-glutamate (FA-Glu), a surfactin variant has been successfully produced using a genetically modified strain of Bacillus subtilis grown on glucose. However, yields with soybean hulls (SBH) replacing glucose were lower. This work was undertaken to reduce the yield loss when using SBH as the carbon source and to evaluate two other soy by-products, namely fiber and skim from aqueous oil extraction as alternative carbon and nitrogen sources. Fermentation of soybean hulls, fibers and skim at various concentrations produced lower FA-Glu titers compared to S-7 medium. Neither increasing their amount nor supplementing with glucose increased the FA-Glu titer, suggesting the presence of an inhibitor in these feedstocks. By using a mixture of polysaccharide-degrading enzymes, over 65% of SBH solids were converted to soluble carbohydrates. FA-Glu titers obtained from SBH hydrolysates containing residual hull solids were still low; however, with the removal of the solids, cell growth improved and FA-Glu yield was 60% higher than with glucose. Thus, this low-cost material can be converted to a substrate for production of FA-Glu biosurfactant. Unmodified fiber and skim components of aqueous oil extraction were not beneficial. (C) 2014 Elsevier BAT. All rights reserved.