Gianluca Maffei

Enhanced Lipid Extraction from Unbroken Microalgal Cells Using Enzymes

The marine microalga Nannochloropsis sp. was chosen as a model organism to investigate the feasibility of using cell wall-degrading enzymes to enhance the recovery of intracellular lipids. An enzyme cocktail containing galactomannanase, 1,4-β-cellobiosidase and β-glucosidase as main components was prepared from commercial enzyme preparations. The effects of pretreatment time (P), enzyme dosage (D), pH and temperature (T) on the amount of extracted lipids were investigated using response surface methodology. Under the best conditions (P = 90 min, D = 1.3 mg g–1, pH = 5, T = 36 °C) over 70 % of the lipids present in the microalga were recovered. SEM and TEM characterization of enzyme-treated microalgae showed extensive cell damage with significant disruption of the cell wall and release of algal material. Overall, the results obtained strongly support the use of commercial enzyme preparations to improve lipid recovery from microalgae and provide useful information on the influence of process conditions on the treatment efficiency.

Effect of an enzymatic treatment with cellulase and mannanase on the structural properties of Nannochloropsis microalgae

The effects of an enzymatic treatment with cellulase and mannanase on the properties of marine microalgae Nannochloropsis sp. were investigated. The combined use of these enzymes synergistically promoted the recovery of lipids from the microalgae, increasing the extraction yield from 40.8 to over 73%. Untreated and enzymatically treated microalgae were characterized by chemical analysis and by TGA/DTG, FTIR, XRD and SEM. Significant changes were observed in the chemical composition and thermal behavior of the microalgae. The enzymatic treatment also resulted in an increase of the crystalline-to-amorphous cellulose ratio. SEM images revealed dramatic changes in cell morphology, extensive cell damage and release of intracellular material. Overall, the results obtained indicate that the enzymes used are capable of disrupting the microalgal cell wall and that a combination of common analytical techniques can be used to assess the enzyme-induced damage.

Evaluation of dissolved organic carbon (DOC) as a measure of cell wall degradation during enzymatic treatment of microalgae

The feasibility of using Dissolved Organic Carbon (DOC) measurements as a means to assess the efficacy of an enzyme-assisted pretreatment on the recovery of lipids from microalgae was investigated. Attention was focused on Nannochloropsis sp., a marine microalga of great biotechnological interest for its ability to accumulate large amounts of lipids and other valuable compounds. The enzymatic pretreatment was carried out using two commercial enzyme preparations, one (CEL) rich in cellulase and the other (GMA) rich in galactomannase. Experiments were performed according to a fractional two-level factorial design. The factors studied were temperature (15–75 °C), pH (2–8), pretreatment time (30– 270 min), CEL dosage (0–20 mg/g) and GMA dosage (0–2 mg/g). DOC was determined by a TOC analyzer and used as the response variable. Under the experimental design conditions, temperature, pH, pretreatment time and CEL dosage were found to be statistically significant (p < 0.05), with the former factor being the most influential. No significant interactions were observed between the main factors, indicating that each of them exerted its effect independently of the others. A good correlation was also found between the measured DOC values and the yields of lipid extraction from the enzymatically treated biomass, demonstrating that DOC measurements can be used to quantify the enzyme-induced degradation of algal cell walls.

Production of Silver Nanoparticles by spent coffee grounds extracts

B is a clean, renewable and abundant resource that can be converted to bio-char, bio-oil and fuel gas through various thermochemical processes. Conversion of biomass for high value products is an important development direction for biomass utilization, which has attracted more attention. In this study, a new method of biomass pyrolysis with exogenous nitrogen introduced was proposed. The influence of NH3 on the property of bamboo pyrolysis process and products characteristics was investigated with variant approaches (e.g. elemental analysis, automatic adsorption equipment, X-ray photoelectron spectroscopy and CHI760 electrochemical workstation) and as well as the influence of KOH (as activator). The results showed that, the specific surface area, the content of nitrogen and nitrogen-containing functional groups of bio-char increased significantly with NH3 introduced in. On the other hand, with the addition of KOH, the yield of bio-char increased obviously and it increased gradually with increasing KOH amount, and the specific surface area increased dramatically to 1873.17 m2 g-1. The content of nitrogen in bio-char increased greatly with KOH introduced in, especially the content of pyridinic-N and pyrrolic/pyridone-N, while it decreased slightly with increasing KOH amount, but nitrogen content was still relative high (9.1-10.4 wt.%). The formation mechanism of nitrogen-containing functional groups was proposed. Besides, electrochemical analysis showed that the specific capacitance of bio-char electrodes increased with increasing KOH content, and the largest specific capacitance could reach to 187 F g-1 at 1 A g-1 with good cycling stability. Therefore, it could be concluded that biomass nitrogen-enriched pyrolysis was a promising method for more efficient utilization of biomass resources.A insoluble palladium catalyst (Pd-pol) was obtained by copolymerization of the metal containing monomer Pd(AAEMA)2 [AAEMA− = deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with ethyl methacrylate (co-monomer) and ethylene glycol dimethacrylate (cross-linker), followed by in situ reduction of Pd(II) to Pd(0), to give polymer stabilized metal nanoparticles. The good swellability in water exhibited by Pd-pol rendered it an ideal potential catalyst for reactions carried out in a green solvent, such as water, since the migration of the reagents to the active sites would not be hampered by the solid support. With the aim to develop innovative catalytic processes that enable chemical transformations to be performed under mild and sustainable conditions with high efficiency, we decided to evaluate the catalytic activity of Pd-pol for several important organic reactions using water as solvent. Pd-pol resulted highly active and selective in catalyzing (figure 1): the Suzuki-Miyaura coupling between aryl bromides or activated aryl chlorides and phenylboronic acid; the oxidation of benzyl alcohols to aldehydes; the reduction of quinolines and nitroarenes by H2 or NaBH4. Pd-pol was recyclable for several consecutive runs (for example, at least 12 times in the nitroarene reduction). TEM analyses carried out on the catalyst showed that the active species were supported palladium nanoparticles having a mean size of 4 nm, which did not aggregate with the recycles. Recently, due to their low cost, Ni catalysts have been employed in several organic reactions (mainly hydrogenations). In this context, we synthetized a Ni catalyst similar to Pd-pol, starting from Ni(AAEMA)2 and we employed it as active and recyclable, insoluble catalyst for the reduction of different nitroarenes to give the corresponding anilines, under sustainable conditions. All these results proved that the proposed Pd or Ni based composite materials are excellent hybrid structures as efficient and reusable catalysts.A amino acids are versatile structures readily available by a number of methods and are accessible using very few transformations from economical starting materials. They can be functionalized by many chemical functions and offer a wide range of possible transformations. Particularly, unsaturated α-amino acids give access to many synthetic applications in all fields of chemistry. Among them, metal catalyzed cross-coupling reactions and cross metathesis are commonly used to generate peptide modifications and cyclization. They are very interesting and useful tools for “Click” Chemistry in peptidomimetic drug design or covalent modification of proteins. They can also be incorporated in compounds as beta-turn inducer to promote secondary structures. Finally they can be used for the preparation of stapled peptides. Some such amino acids are commercially attainable in enantiomerically pure form. Here, we present a stereoselective approach to synthesize unsaturated α-amino acids in optically active form. As a starting amino acid synthon for the asymmetric synthesis of amino acids NiII square-planar complexes of Schiff ’s bases of propargylglycine with chiral auxiliary (S)-2-N-(N`-benzyl-prolyl)aminobenzophenone (BPB) (1) was taken. As a result effective methods of asymmetric synthesis for novel enantiomerically enriched derivatives of (S)-propargylglycine (S)-propargylglycine (ee > 80%) was developed.

Adsorption and regeneration of fluoride ion on a high alumina content bauxite

Adsorption of fluoride ion from aqueous solutions by using different silico-aluminous natural products was studied. Preliminary batch tests indicated how bauxite shows a high removal efficiency. Such optimum efficiency is due to the elevated presence of aluminium hydroxide (gibbsite) and aluminium oxide hydroxide (boehmite). Both batch and continuous experiments were performed: Freundlich equation well described batch equilibrium data. In continuous-flow column experiments, the effects of inlet fluoride concentration (5–50 mg L) and flow rate (up to 2.5 mL min) on breakthrough time and adsorption capacity were studied. Column studies showed that the dynamic adsorption capacity depends on the inlet fluoride concentration and the flow rate. After adsorption of fluorides, saturated bauxite, was regenerated by using two different solutions containing NaOH and H2SO4. Column tests indicated a different behaviour of original respect to regenerated bauxite.