Leonardo Setti

Synthesis of pentylferulate by a feruloyl esterase from Aspergillus niger using water-in-oil microemulsions

Pentylferulate synthesis was achieved at high yields (50–60%) with Aspergillus niger feruloyl esterase using a water-in-oil microemulsion system. The initial rate of synthesis decreased by 15–20% when the water content of the microemulsion was increased from 1.8 to 2.4% (v/v), although a concomitant decrease in conversion was not observed. The enzyme stability was significantly higher in the microemulsion than in an aqueous solution.

Laccase catalyzed-oxidative coupling of 3-methyl 2-benzothiazolinone hydrazone and methoxyphenols

Abstract The reaction between o -, m -, and p -methoxyphenols and 3-methyl-2-benzothiazolinone hydrazone was studied in the presence of laccase from Pyricularia oryzae . The findings show that laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) catalyzes the oxidative coupling reaction between MBTH and phenols producing red colored azo-dye compounds. On the basis of kinetic parameters and optimum pH values, the mechanisms of the oxidative coupling reactions with the different phenols are discussed. The results suggest that the reaction is initialized by the enzymatic 3-methyl-2-benzothiazolinone hydrazone activation, which undergoes electrophilic substitution with m -methoxyphenol in solution, enzymatic activated guaiacol, and chelated p -methoxyphenol at the catalytic site of the laccase. The current study also demonstrates the possibility of using the azo-dye formed in the presence of guaiacol for measuring laccase activity following a similar assaying method as that used for measuring peroxidase activity. This type of assay permits the determination of laccase at micromolar levels by fixed time method.

Thermal Inkjet Technology for the Microdeposition of Biological Molecules as a Viable Route for the Realization of Biosensors

Abstract Recent progress in inkjet printing of parts of biosensors are highlighted, with particular reference to the printing of biologically active molecules. We describe a system constituted by a thermal inkjet printer, adapted to layering a bidimensional array of dots [701 × 701 dots per inch] on solid supports. The printer was used to depose a β‐galactosidase (GAL)‐containing ink on a polyester sheet, with dots obtained from 10 pL drops, each drop containing in turn 6 pg of enzyme. The activity of GAL after the preparation was determined using a colorimetric probe (Brilliant Blue FCF). The activity loss of the microdeposed enzymes was found to be around 15%, showing that the 2 µsec‐lasting thermal shock experienced by the biomolecule into the printhead nozzle affects to a lesser extent the activity of the thermal inkjet deposited enzyme. In conclusion, the most recent findings of our group in this line are depicted, and a view of possible future developments of the “biopolytronics” field is outlined.

Further research into the aerobic degradation of n-alkanes in a heavy oil by a pure culture of a Pseudomonas sp

Abstract The microbial degradation of the saturated fraction of a heavy oil was examined in aerobic conditions employing a pure culture of a Pseudomonas sp. isolated from soil. A new model of n -alkane degradation is proposed. The n -alkanes were divided into three degradation groups: i) liquid n -alkanes, C12C16; ii) low solid n -alkanes, C17C28; iii) high solid n -alkanes, above C28. Our results show that n -alkane degradation depends on chemical and physical factors such as solubility and surface tension.

Immobilization of Lipase on microporous and mesoporous materials: studies of the support surfaces

Abstract In this paper the performance of different supports respect to the lipase immobilization was investigated. The used enzyme was the lipase from Rhizomucor miehei (RML - commercial name: Palatase). The immobilization tests on mesoporous materials (MCM-41), de laminated zeolites (ITQ-2 and ITQ-6), Na-Silicalite-1, H-Silicalite-1 and F AU zeolites, were carried out by adsorption. The pore size, morphology, crystal dimension, acidity, hydrophobicity and chemical composition of the supports, strongly influence the amount of the enzyme adsorbed. The Na-silicalite-1 support shows the best lipase immobilization capacity, with an efficiency of c.a. 74% respect to the 41% of MCM-41 and the 27% of ITQ-2 type materials, while no enzyme is retained on the zeolite FAU (zeolite X). The preliminary activity tests using the lipase-support as a catalyst, were carried out for the reaction of hydrolysis of triglycerides. The activity observed for the lipase-Na-Silicalite-1 and the lipase-MCM-41 catalysts is 86% and 78%, respectively, respect to the activity of the free lipase enzyme in solution.

Dibenzothiophene biodegradation by a Pseudomonas sp. in model solutions

Abstract The presence of fatty acid and an n -alkane may affect the biodegradation rate of aromatic sulphur compounds such as dibenzothiophene (DBT). A fatty acid (hexadecanoic acid) may form micellar structures favouring DBT bioavailability. n -Alkanes, such as n -dodecane or n -hexadecane, form a film around the aromatic sulphur molecule as a consequence of solvation, thus increasing DBT bioavailability. The mass-transfer rate from the solid to the aqueous phase controls the DBT biodegradation rate when DBT is the only carbon source. Diffusional coassimilation and microbial hydrophobic effects are rate-limiting steps in DBT biodegradation in the presence of aliphatic compounds. Diffusion depends on the DBT concentration in n -alkane, while cometabolism is associated with different n -alkane biodegradation rates. Through the definition of biodesulphurization selectivity and biodersulphurization efficiency, our investigations have shown that a selective aerobic biodesulphurization process is possible by using an unselective biocatalyst, such as a Pseudomonas sp.

Study of lipase immobilization on zeolitic support and transesterification reaction in a solvent free-system

In order to understand the role of the acid–base, electrostatic and covalent interactions between enzyme and support, the catalytic behavior of the Rhizomucor miehei lipase (RML) immobilized on zeolite materials has been studied. The highest lipase activities were obtained when this enzyme, immobilized by adsorption, interacts through acid–base binding forces with the support surface, resulting in activation of the enzyme catalytic center. Due to the interest in biodiesel production by mild enzymatic transesterification, this heterogeneous biocatalyst has been used in transesterification of fatty acids contained in olive oil. The results show a high oleic acid conversion for several reaction cycles with a higher total biodiesel productivity compared to that using the free enzyme.

Whole cell biocatalysis for an oil desulfurization process

Copyright (c) 1997 Elsevier Science B.V. All rights reserved. Various attempts have been made to develop biotechnological processes based on microbiological desulfurization employing aerobic and anaerobic bacteria. In order to obtain a biodesulfurization process competitive with the chemical-physical one of hydrodesulfurization (HDS), a biotechnological process has to follow the three main refinery steps: 1) separation, entailing some pretreatment of crude oil; 2) conversion, i.e. biocatalytic transformation where the biocatalyst favours a selective desulfurization process without destroying useful products; 3) finishing, in which the crude oil is separated from the biocatalyst and the byproducts. Biocatalysis may be carried out using whole cells or isolated enzymes in the free or immobilized form. The use of isolated enzymes is advantageous since it avoids the formation of undesirable byproduct mediated by contaminating enzymes as in the case of the aerobic biodesulfurization, which is not a selective process. In fact, the aerobic microorganisms may degrade almost all the compounds which make up the heavy oil. However, despite this advantage, extraction and purification of the enzyme is costly and, frequently, enzymes catalyzing oxidation-reduction reactions require enzyme cofactors which must be regenerated after the reaction. For these reasons, metabolic conditions can often be designed by using whole cell biotransformations to promote cofactor regeneration, thus avoiding the problems associated with cofactor recycling and regeneration. Today, the main limitations for the industrial application of a biodesulfurization process are associated with the high cost of the biocatalyst and with the volumetric ratio between the organic phase and the aqueous one. In order to overcome these problems, cell immobilization is one of the most promising approaches in terms of treatment costs and in finishing step times when compared to a continuous stirred tank bioreactor for the biodesulfurization process.

The effect ofn-alkanes in the degradation of dibenzothiophene and of organic sulfur compounds in heavy oil by aPseudomonas sp.

SummaryThe microbial degradation of organic sulfur compounds was examined in aerobic conditions employing a pure culture of aPseudomonas sp., isolated from the soil. The effect ofn-alkanes on the degradation of dibenzothiophene (DBT) showed that the assimilation of the sulfur compound by the microorganism is favoured byn-dodecane. Moreover, the saturated fraction was seen to enhance the degradation of the sulfur compounds to be found in a deasphaltenated heavy oil.

Enhanced degradation of heavy oil in an aqueous system by a Pseudomonas sp. in the presence of natural and synthetic sorbents

The microbial degradation of the saturated and sulfur aromatic fractions of a heavy oil was examined in aerobic aqueous conditions employing a pure culture of a Pseudomonas sp. in the presence of natural and synthetic sorbents. All three natural sorbents tested (keratin, chitosan and chitin) were capable of adsorbing large amounts of heavy oil as well as enormously increasing the n-alkane biodegradation rate and decreasing the lag phase by up to five-seven times as much as that in the absence of sorbents. In the presence of natural sorbents n-alkane biodegradation was complete after 7 days while in their absence the same result took 40 days. This time decrease was ascribed to an improved interaction between the oil and the microorganisms derived from the formation of a water/cell/oil/sorbent interphase. The values of the accelerating conversion factor, b, and the length of the lag phase, 1/ab, were determined for the different sorbents using a mathematical expression, and they could represent two important parameters for the description of n-alkane biodegradation kinetics.