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Immobilization of Biocatalysts onto Nanosupports: Advantages for Green Technologies
Published in Grunwald Peter, Biocatalysis and Nanotechnology, 2017
Alan S. Campbell, Andrew J. Maloney, Chenbo Dong, Cerasela Z. Dinu
The most commonly studied enzyme used to catalyze the transesterification reaction is lipase, which offers substantial advantages to the process as a whole, but is not widely implemented due to the high costs mentioned. However, due to strides in enzyme immobilization technology, many immobilized enzyme-based systems have become commercially available to meet the need of more environmentally friendly biodiesel production (Bajaj et al., 2010; Zhang et al., 2012). Currently, lipase systems commercialized under the names Novozyme 435 produced by Novozyme and LS-10 A produced by Beijing CTA New Century Biotechnology Co., Ltd. are two of the most widely utilized systems. Adsorption of lipase onto a textile membrane lowered methanol toxicity to the enzyme and increased recoverability in the case of LS-10 A, allowing for an esterification rate greater than 95% with a stability of 210 h. Similarly, adsorption onto an acrylic resin increased the stability of lipase in acidic conditions for Novozyme 435 allowing for biodiesel yields of 90% and a stability of 500 h, but decreases in the cost of lipase are needed for more widespread use (Bajaj et al., 2010; Zhang et al., 2012). Similar trends have also been reported using supports such as silica nanocomposites, CNTs, gold nanoparticles and magnetic iron oxide nanoparticles, with greater increases in stability and recovery due to increased enzyme loadings, improved mass transfer of substrate and product to the enzymes and enhanced mobility of the conjugates themselves (Wang et al., 2011; Ranjbakhsh et al., 2012; Tran et al., 2012; Verma et al., 2013). For instance, Pavlidis et al. investigated the covalent attachment of lipase onto CNTs and reported increased temperature stability and activity with a 60% improvement of catalytic efficiency (Pavlidis et al., 2012). Incorporation of these nanosupport immobilized enzyme systems has the potential to drastically improve biodiesel production practices.
Methanol
Published in Arumugam S. Ramadhas, Alternative Fuels for Transportation, 2016
Mustafa Canakci, Oguzhan Ilgen
The toxicity of methanol is well known. Ingestion of relatively small amounts will lead to blindness and slightly larger amounts, to death. While individual responses to methanol vary widely, one report claims that ingestion of as little as 300–1000 mg/kg (0.85–2.85 ounces for a 150 pound person) can cause death (Kavet and Nauss 1990). Methanol is easily and rapidly absorbed by all routes of exposure and distributes rapidly throughout the body. Humans absorb 60–85% of the methanol that is inhaled. A small amount is excreted by the lungs and kidneys without being metabolized. The rate of metabolism for methanol in the body is (25 mg/kg hour), which is seven times slower than for ethanol and is independent of concentrations in the blood. Humans metabolize methanol into CH2O as the first step. The CH2O is then converted to formic acid (CH2O2), which can be toxic at high concentrations, and finally to CO2 and H2O. The half-life of methanol elimination in expired air after oral or dermal exposure is 1.5 hours. Due to their limited capability to metabolize CH2O2 to CO2, humans accumulate CH2O2 in their bodies from high-dose methanol exposure. If CH2O2 generation continues at a rate that exceeds its rate of metabolism, methanol toxicity sets in. Background levels of methanol in the human body will not result in CH2O2 accumulation or adverse health effects. Studies have shown that short-term inhalation exposure to 200 ppm methanol results in blood methanol concentrations of less than (10 mg/l) with no observed increase in blood CH2O2 concentration (www.methanol.org 2008).
Bio-catalytic transesterification of mustard oil for biodiesel production
Published in Biofuels, 2022
Qurrat Ul Ain Rana, Muhammad Irfan, Safia Ahmed, Fariha Hasan, Aamer Ali Shah, Samiullah Khan, Fazal Ur Rehman, Haji Khan, Meiting Ju, Weizun Li, Malik Badshah
The alcohol used for transesterification in this study was methanol, which is known to inhibit microbial growth. However, certain microbial species possess the ability to tolerate low levels of methanol [23]. In order to determine the extent to which P. aeruginosa strain Q8 KX712304 can tolerate methanol, a methanol toxicity test was employed. For this purpose, 5% 24-h enriched culture was inoculated in nutrient broth containing 5%, 10% and 15% methanol. It was then incubated at 37 °C for 72 h and growth optical density (OD) was monitored every 24 h at 650 nm.