In spite of the limited sources of fossil fuels, energy demand has been considerably increased since the last century. The problems associated with global warming due to rising atmospheric greenhouse gas levels and scarcity of fossil fuels make it imperative to reduce our heavy dependency on fossil fuels. These reasons forced countries throughout the world to search for new fuel alternatives. Biofuel have gathered considerable attention due to their inherent benefits, like lower greenhouse gas emission, renewability, and sustainability. Commercially, biofuels are produced from vegetable oils, animal fats, and carbohydrates by using transesterification and fermentation. However, biofuel production suffers from high production costs and other technical barriers. Considering the environmental and economic issues, use of nanotechnology seems to be a viable solution. Nanoparticles have a number of interesting properties for the production of second-generation ethanol or transesterification of oils and fats to yield biodiesel. It is advantageous for recovery and reuse of catalysts. The present review discusses the role of nanotechnology in the production of bioethanol and biodiesel. Moreover, applications of nanoparticles for the production of biodiesel and second-generation ethanol with special reference to enzyme immobilization and chemical nano-catalysis have been described.

In spite of the limited sources of fossil fuels, energy demand has been considerably increased since the last century. The problems associated with global warming due to rising atmospheric greenhouse gas levels and scarcity of fossil fuels make it imperative to reduce our heavy dependency on fossil fuels. These reasons forced countries throughout the world to search for new fuel alternatives. Biofuel have gathered considerable attention due to their inherent benefits, like lower greenhouse gas emission, renewability, and sustainability. Commercially, biofuels are produced from vegetable oils, animal fats, and carbohydrates by using transesterification and fermentation.However, biofuel production suffers from high production costs and other technical barriers. Considering the environmental and economic issues, use of nanotechnology seems to be a viable solution. Nanoparticles have a number of interesting properties for the production of second-generation ethanol or transesterification of oils and fats to yield biodiesel. It is advantageous for recovery and reuse of catalysts. The present review discusses the role of nanotechnology in the production of bioethanol and biodiesel. Moreover, applications of nanoparticles for the production of biodiesel and second-generation ethanol with special reference to enzyme immobilization and chemical nano-catalysis have been described. Keywords: biodiesel; biofuel; ethanol; immobilization; nanotechnology; renewable resources Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.

L-asparaginase is the enzyme responsible for converting the amino acid L-asparagine into L-aspartic acid and ammonium. This enzyme has important applications, mainly in the pharmaceutical industry, where it is used as an antileukemic drug, and in the food industry, as a treatment for mitigating the formation of acrylamide, a highly toxic compound produced in some foods exposed to high temperatures. Yeasts are highlighted as important microorganisms for the production of L-asparaginase since they are capable of producing enzymes with fewer side effects for humans and are, in general, GRAS organisms, being applicable in the food industry without restrictions. This study evaluated screening methods for selecting new yeasts capable of producing L-asparaginase, selecting those capable of producing high amounts of this enzyme from a culture collection containing 40 strains, also verifying aspects of enzyme production. Methods for screening L-asparaginase producing organisms in solid and liquid medium were tested, evaluating the applicability of Nessler and hydroxylamine methods as means for enzyme activity quantification. The production of L-asparaginase was later confirmed through thin layer chromatography. The selected yeasts were evaluated to confirm the influence of the amino acids L-asparagine, L-proline and L-glutamine as inducers in the production of L-asparaginase, and the kinetics of Lasparaginase production were also evaluated. According to the results, none of the assessed yeasts were able to produce extracellular L-asparaginase. However, two novel yeasts, so far not cited in the pertinent literature as L-asparaginase producers, were able to produce periplasmic L-asparaginase: Issatchenkia orientalis and Rhodotorula glutinis. Tests also verified that the screening methods in solid medium did not correlate with the production of L-asparaginase in liquid medium by yeasts. It was necessary to add inducing molecules, such as the amino acids L-asparagine, L-proline and L-glutamine, to stimulate L-asparaginase production by the yeasts I. orientalis and R. glutinis. The highest production of periplasmic L-asparaginase was obtained in liquid medium supplemented with Lasparagine and ammonium nitrate for the yeast I. orientalis (20,38 ± 3,55 U.g -1 ) and in medium supplemented with L-proline for the yeast R. glutinis (57,05 ± 0,57 U.g -1 ). The production kinetics assay verified that the production of the enzyme took place mainly during the log phase of microbial growth, being stable after144 hours of cultivation. The results presented in this study were able to confirm the viability of the methods for the screening of novel L-asparaginase producing yeasts as well as to select two novel yeasts able to produce this enzyme, I. orientalis and R. glutinis, determining some important aspects in L-asparaginase production in liquid medium.