Enzymatic hydrolysis of steryl glucosides, major contaminants of vegetable oil-derived biodiesel

Abstract

Biodiesels are mostly produced from lipid transesterification of vegetable oils, including those from soybean, jatropha, palm, rapeseed, sunflower, and others. Unfortunately, transesterification of oil produces various unwanted side products, including steryl glucosides (SG), which precipitate and need to be removed to avoid clogging of filters and engine failures. So far, efficient and cost-effective methods to remove SGs from biodiesel are not available. Here we describe for the first time the identification, characterization and heterologous production of an enzyme capable of hydrolyzing SGs. A synthetic codon-optimized version of the lacS gene from Sulfolobus solfataricus was efficiently expressed and purified from Escherichia coli, and used to treat soybean derived biodiesel containing 100 ppm of SGs. After optimizing different variables, we found that at pH 5.5 and 87 °C, and in the presence of 0.9 % of the emulsifier polyglycerol polyricinoleate, 81 % of the total amount of SGs present in biodiesel were hydrolyzed by the enzyme. This remarkable reduction in SGs suggests a path for the removal of these contaminants from biodiesel on industrial scale using an environmentally friendly enzymatic process.

Sterylglucoside Catabolism in Cryptococcus neoformans with Endoglycoceramidase-related Protein 2 (EGCrP2), the First Steryl-β-glucosidase Identified in Fungi

“…Similar activity was found in Sinapis alba (34) and Sulfolobus solfataricus (35); however, these enzymes show no sequence homology with EGCrP1/EGCrP2. In addition, it remains unclear whether these plant and archaea enzymes are actually involved in sterylglucoside metabolism in vivo because knock-out of the corresponding genes in plants and archaea has not been reported.…”

The infectious intracellular lifestyle ofSalmonella entericarelies on the adaptation to nutritional conditions within theSalmonella-containing vacuole

“…28,76 Glucose in the supernatant was specifically converted to 6-phosphogluconate in a coupled enzymatic reaction (hexokinase, glucose 6-phosphate dehydrogenase), with formation of NADPH, which was determined fluorometrically at 340 nm in a Synergy 2 Multi-Mode Microplate Reader (BioTek). 77 Bacterial infection of macrophages RAW 264.7 macrophages were seeded at a density of 4£10 5 cells per well in 6-well tissue culture plates in DMEM-based growing medium with different glucose concentration or 400 mM oleic acid. Macrophages were supplemented with IFN-g (10 U ml ¡1 , ImmunoTools) 24 hours before use.…”

The in-process removal of sterol glycosides by ultrafiltration in biodiesel production

“…Accordingly, several studies aimed at reducing SG levels in finished biodiesel have been carried out. Enzymatic removal has been shown to reduce SG levels by 81% with the addition of a synthetic codon-optimized version of the LacS gene expressed from E. Coli (Aguirre et al, 2014). This enzyme is water-soluble, and so, the hydrolysis of SG is mass transfer-limited between the aqueous phase and biodiesel phase.…”