Gisela Montero

Enhanced Production of Extracellular Lipase by Novel Mutant Strain of Aspergillus Niger

ABSTRACT Twelve fungal strains belonging to 9 different species of genera Aspergillus, Pencilillium, Trichoderma and Mucor were screened for extracellular lipase production. The most active lipase producing strain A. niger was selected for strain improvement by induced mutagenesis with UV light and N-methyl-N-nitro-N-nitrosoguanidine (NMG). Chemical mutagenesis was found to be more effective in comparison to the physical one. By two stages mutagenesis with 200 μg cm−3 NMG for 4 h, lipase activity of parental strain was enhanced more than two times. The selected mutant A. niger NMG12/4 was stable and maximum lipase activity of 15.5 U cm−3 was reached at 96 h, which corresponded to the end of the exponential growth phase. The selected mutant is prospective for the development of industrial biotechnology for production of extracellular lipase.

The Immobilized Lipases in Biodiesel Production

Recently, biodiesel production by lipase catalyzed transesterification has been suggested as a promising alternative to the conventional chemical catalysis, in spite of the high conversion and reaction rates of the latter (Akoh et al., 2007; Bajaj et al., 2010; Bisen et al., 2010; Demirbas, 2009; Fjerbaek et al., 2009; Fukuda et al., 2001, 2009; Ghaly et al., 2010; Helwani et al., 2009; Jegannathan & Abang, 2008; Man Xi Ao et al., 2009; Marchetti et al., 2007; Ranganathan et al., 2008; Robles-Medina et al., 2009; Semwal et al., 2011). The enzymatic process enables eliminating the drawbacks of the alkalior acid-catalyzed transesterification, namely: product contamination, wastewater release, free fatty acids and water interferences, and difficult glycerol recovery. Nevertheless, the commercialization of

Lipase Production Through Solid-State Fermentation using Agro-Industrial Residues as Substrates and Newly Isolated Fungal Strains

ABSTRACT Extracellular lipase production by Penicillium chrysogenum, Trichoderma harzianum and Aspergillus flavus was carried out through solid state fermentation using agro-industrial residues as substrates. For all three strains, the growth temperature was 29±1 °C, and 65% w (g/gds) moisture content. The effect of three factors on lipase production rate was investigated: initial pH (6.0 and 7.0), time of fermentation (72 h, 96 h and 120 h), and type of mixed substrate (wheat bran-olive oil, and wheat bran-castor oil cake). The process was optimized applying a mixed level factorial design. Fermentation time and pH were found to have positive effects on lipase production and secretion rates. However, the time effect was larger than initial pH. Type of substrate demonstrated minor effective importance than the other two factors, and Aspergillus flavus showed the larger lipase production among the three strains. Results indicated that the three fungal strains were able to grow and produce lipase in both culture mediums. The maximum lipase activity achieved was 121.35 U/gds by Aspergillus flavus, which was five and nine times the lipase produced by Trichoderma harzianum and P. chrysogenum respectively, at the same conditions. An initial neutral pH and 96 h of fermentation time were the optimum conditions for lipase production by Aspergillus flavus.

Production and Partial Characterization of Extracellular Lipase from Trichoderma Harzianum by Solid-State Fermentation

ABSTRACT The growing interest in lipase production is related to the potential biotechnological applications that these enzymes present. Current studies on lipase production by solid state fermentation involve the use of agro-industrial residues, aiming at increasing the economic attractiveness. Based on these aspects, the objective of this work was to investigate lipase production by a local strain Trichoderma harzianum in solid-state fermentation (SSF), using wheat bran as a solid substrate, and compare this lipase production with submerged fermentation (SmF) using a mineral culture medium. The maximum lipase activity, 1.82 UmL−1 ± 0.01 UmL−1, was obtained during submerged fermentation in a medium containing 2% sucrose and 2% olive oil. However, 71.3 Ug−1 ± 1.48 Ug of dry solid substrate equivalent to 14.3 UmL−1 of lipase activity was reached using a solid-state fermentation process with a medium containing 0.75% ammonium sulphate and 0.34 % urea, 2% olive oil and wheat bran as a solid substrate. The pH and temperature optima for lipase were 8.03 and 40 °C, respectively. The Michaelis constant (KM = 6.6 mmol-L−1) was obtained from two different plots, i.e. Lineweaver—Burk and Hanes—Woolf. Vmax of the enzyme reaction was found to be 7.5 U-mL−1.

Comparison of the performances of four hydrophilic polymers as supports for lipase immobilisation

Four hydrophilic polymers in the form of beads – chitosan, alginate, alginate/polyvinyl alcohol (PVA), and chitosan-coated alginate – were used as supports for lipase immobilisation. Hydrogel beads were characterised by bead-size-distribution estimation, surface morphology studies, and polymer interactions assessment. Matrix performances – loading efficiency, immobilisation yield, enzyme activity, and stability retention – were evaluated and compared. Although the loading efficiency of the chitosan-coated Ca-alginate beads (79.8%) was inferior to that of the Ca-alginate (87%) and of the Ca-alginate/PVA beads (81.3%), their enzyme immobilisation yield (63.96%) was the most important. Moreover, lipase encapsulated in chitosan-coated Ca-alginate beads demonstrated better pH, thermal, and storage (89% residual activity after 30 days) stabilities. Immobilised lipase activity also increased in the order: alginate/PVA > chitosan > alginate > alginate/chitosan, and displayed a maximum at pH 8 and at temperatures of 45 °C (chitosan and Ca-alginate/PVA beads) and 50 °C (Ca-alginate and chitosan-coated Ca-alginate beads). Thus, chitosan-coated Ca-alginate beads could be considered as a suitable support for lipase immobilisation.

Amperometric biosensor precision improvement: application to organophosphorus pesticide determination

An approach for precision improvement in organophosphorus pesticide determination was developed, applied and characterized. The enzyme organophosphorus hydrolase was employed as a specific agent for electrode surface modification, and the pulsed amperometric detection for 66.6 ms was applied for the hydrolysis product detection. Pulsed electrochemical cleaning, i.e. oxidation at a very positive potential (+1.4 V vs. Ag, AgCl) was applied every 233 ms for 166.6 ms for elimination of the fouling effect, which degrades the determination precision. By this way a RSD of 0.41% at 40 μmol L−1p-nitrophenol determination was achieved after 10 determinations, instead of 43.93% without the pulsed cleaning application.

Nutritive Medium Engineering Enhanced Production of Extracellular Lipase by Trichoderma Longibrachiatum

ABSTRACT The influence of six different plant oils, oleic acid, linoleic acid and different nitrogen sources on the production of extracellular lipase by Trichoderma longibrachiatum in submerged fermentation was studied. It was obtained that enzyme production strongly depended on the nutritive medium composition. The decreasing of oleic acid content and increasing of linoleic acid content decreased the production of extracellular lipase by Trichoderma longibrachiatum. Inorganic nitrogen sources, in particular (NH4)2SO4, stimulated lipase production. As a result of the applied mathematical modeling and optimization procedure the optimal nutritive medium composition was determined. In the optimized nutritive medium maximum lipase activity 13.98 U-cm−3 was reached at 72 h, which corresponded to the end of the exponential growth phase. As a result of the applied optimization procedures almost 2.5 times increasing of lipase production was achieved in comparison with basal medium.

Solar Energy for a Solvent Recovery Stage in a Biodiesel Production Process

Recent research and development of clean energy have become essential due to the global climate change problem, which is caused largely by fossil fuels burning. Therefore, biodiesel, a renewable and ecofriendly biofuel with less environmental impact than diesel, continues expanding worldwide. The process for biodiesel production involves a significant energy demand, specifically in the methanol recovery stage through a flash separator and a distillation column. Traditionally, the energy required for this process is supplied by fossil fuels. It represents an opportunity for the application of renewable energy. Hence, the current study presents a system of thermal energy storage modeled in TRNSYS® and supported by simulations performed in ASPEN PLUS®. The aim of this research was to supply solar energy for a methanol recovery stage in a biodiesel production process. The results highlighted that it is feasible to meet 91% of the energy demand with an array of 9 parabolic trough collectors. The array obtained from the simulation was 3 in series and 3 in parallel, with a total area of 118.8 m2. It represents an energy saving of 70 MWh per year.

Virtual Instrument for Emissions Measurement of Internal Combustion Engines.

The gases emissions measurement systems in internal combustion engines are strict and expensive nowadays. For this reason, a virtual instrument was developed to measure the combustion emissions from an internal combustion diesel engine, running with diesel-biodiesel mixtures. This software is called virtual instrument for emissions measurement (VIEM), and it was developed in the platform of LabVIEW 2010® virtual programming. VIEM works with sensors connected to a signal conditioning system, and a data acquisition system is used as interface for a computer in order to measure and monitor in real time the emissions of O2, NO, CO, SO2, and CO2 gases. This paper shows the results of the VIEM programming, the integrated circuits diagrams used for the signal conditioning of sensors, and the sensors characterization of O2, NO, CO, SO2, and CO2. VIEM is a low-cost instrument and is simple and easy to use. Besides, it is scalable, making it flexible and defined by the user.

Detection of Phenolic Compounds by Tyrosinase Modified Clark Type Electrode

In this work is suggested a Clark type electrode with disposable enzyme membrane for phe- nols determination. This approach allows avoiding the electrode fouling by recording the oxygen re- duction current, and obtaining a stable and reproducible sensor response. An appropriate method for enzyme membrane fabrication by cellulose acetate filters coating with tyrosinase through the use of biocompatible hydrogels was proposed and tested. The sensitivity of the catechol determination, as an example, was found to be 0.89 ∝A mmol -1 L. The detection limit equaled 1 ∝mol L -1 . The achieved RSD was 1.22%.