Vincenza Calabrò

An integrated centrifugation–ultrafiltration system in the treatment of olive mill wastewater

Abstract A novel approach in the treatment of olive mill wastewater is presented. Aim of the proposed process is both the reduction of pollution caused by the wastes and the selective separation of some useful products that are present (fats, sugars, polyphenols, etc.). The treatment consists in a preliminary centrifugation step, in which the suspended solids are removed, and in an actual selective separation phase, carried out by ultrafiltration (UF), of the centrifuge supernatant. The combination of centrifugation and ultrafiltration allows a COD reduction of about 90%. Moreover a complete separation of fats, completely rejected by the membrane, from salts, sugars and polyphenols, contained in the permeate, is attained. The present experimental study is directed to investigate the fluid-dynamic aspects related to the ultrafiltration of real olive mill wastewaters. It is based on a preliminary rheological characterization of the waste and on the evaluation of permeation efficiency that was analyzed as a function of several parameters such as the importance of pre-treating wastewater, the effects of localized turbulence, promoted by UF module geometry, and of the main operating variables (trans-membrane pressure and feed flow rate). UF experimental results, obtained in a lab-scale flat-sheet membrane module, are interpreted using both the cake-filtration and the resistance-in-series models, thus allowing the evaluation of Rf parameter that represents the effect of fouling on separation efficiency. An estimation of specific cake resistance, α, is, therefore, performed on the basis of the feed concentration of total non-water compounds present in the waste showing that pre-treated wastewaters give a lower α with respect to raw wastewaters by a factor of about 1000. Moreover, it is found that at the same TMP, lower values of α correspond to a greater Re and that higher local turbulence implies lower specific cake resistances. The results obtained in the present paper could give useful indications for a preliminary characterization of pilot and industrial modules utilized for olive mill wastewaters treatment aimed at a significant COD reduction and a selective separation of valuable compounds that are present in the waste.

Membrane distillation in the textile wastewater treatment.

Abstract Membrane Distillation has been used to produce pure water and to concentrate various kind of solutions at saturation conditions or to separate alcohol-water solutions. Recently this process has been used in the wastewater treatment i.e. to produce pure water and to recovery chemicals from textile wastewater treatment. In this work the experimental analysis of dye solutions treatment has been carried out. Distillate flux and purity, concentration factor and temperature polarization coefficients (TPC) have been measured and their functionalities as function of temperatures and axial flow rate have been analysed. Finally, the energy efficiency (EE) of the experimental system has been evaluated and the potentiality of these applications has been estimated.

Membrane distillataion in the treatment of aqueous solutions

Abstract When a microporous membrane separates two aqueous solutions at different temperatures, selective mass transfer across the membrane can be obtained. The driving force is the vapour pressure difference between the liquids at the two solution-membrane interfaces. A capillary polypropylene membrane has been tested at different temperature differences, solute concentrations, etc. Interesting transmembrane fluxes and selectivities have been consistently observed. The possibility of operating at very high solute concentrations up to saturation has been demonstrated.

The State of the Art in the Production of Fructose from Inulin Enzymatic Hydrolysis

ABSTRACT The present work reviews the main advancements achieved in the last decades in the study of the fructose production process by inulin enzymatic hydrolysis. With the aim of collecting and clarifying the majority of the knowledge in this area, the research on this subject has been divided in three main parts: a) the characteristics of inulin (the process reactant); b) the properties of the enzyme inulinase and its hydrolytic action; c) the advances in the study of the applications of inulinases in bioreactors for fructose production. Many vegetable sources of inulin are reported, including information about their yields in terms of inulin. The properties of inulin that appear relevant for the process are also summarized, with reference to their vegetable origin. The characteristics of the inulinase enzyme that catalyzes inulin hydrolysis, together with the most relevant information for a correct process design and implementation, are described in the paper. An extended collection of data on microorganisms capable of producing inulinase is reported. The following characteristics and properties of inulinase are highlighted: molecular weight, mode of action, activity and stability with respect to changes in temperature and pH, kinetic behavior and effect of inhibitors. The paper describes in detail the main aspects of the enzyme hydrolysis reaction; in particular, how enzyme and reactant properties can affect process performance. The properties of inulinase immobilized on various supports are shown and compared to those of the enzyme in its native state. Finally, a number of applications of free and immobilized inulinases and whole cells in bioreactors are reported, showing the different operating procedures and reactor types adopted for fructose production from inulin on a laboratory scale.

Hydrolysis of Lignocellulosic Biomass: Current Status of Processes and Technologies and Future Perspectives

Bioethanol can be produced from several different biomass feedstocks: sucrose rich feedstocks (e.g. sugar-cane), starchy materials (e.g. corn grain), and lignocellulosic biomass. This last category, including biomass such as corn stover and wheat straw, woody residues from forest thinning and paper, is promising especially in those countries with limited lands availability. In fact, residues are often widely available and do not compete with food production in terms of land destination. The process converting the biomass biopolymers to fermentable sugars is called hydrolysis. There are two major categories of methods employed. The first and older method uses acids as catalysts, while the second uses enzymes called cellulases. Feedstock pretreatment has been recognized as a necessary upstream process to remove lignin and enhance the porosity of the lignocellulosic materials prior to the enzymatic process (Zhu & Pan, 2010; Kumar et al., 2009). Cellulases are proteins that have been conventionally divided into three major groups: endoglucanase, which attacks low cristallinity regions in the cellulose fibers by endoaction, creating free chain-ends; exoglucanases or cellobiohydrolases which hydrolyze the 1, 4glycocidyl linkages to form cellobiose; and β-glucosidase which converts cellooligosaccharides and disaccharide cellobiose into glucose residues. In addition to the three major groups of cellulose enzymes, there are also a number of other enzymes that attack hemicelluloses, such as glucoronide, acetylesterase, xylanase, β-xylosidase, galactomannase and glucomannase. These enzymes work together synergistically to attack cellulose and hemicellulose. Cellulases are produced by various bacteria and fungi that can have cellulolytic mechanisms significantly different. The use of enzymes in the hydrolysis of cellulose is more effective than the use of inorganic catalysts, because enzymes are highly specific and can work at mild process conditions. In spite of these advantages, the use of enzymes in industrial processes is still limited by

Factor analysis of transesterification reaction of waste oil for biodiesel production.

In the present paper a factor analysis is presented for the enzymatic transesterification of waste oil for biodiesel production. The experimental data on batch reactor evidence two key variables: enzyme loading and mixing conditions. These variables were subjected to a factor analysis and their combined effect on the reaction performance was determined. Response surface methodology (RSM) was used based on a linear first order model (steepest ascent method) and on a second order one in proximity of the optimal solution. The result was a model able to predict reaction performance within the range of mixing rates and enzyme amount considered for model formulation and outside of it, as shown in the final validation. Best performances were obtained at high stirring and high enzyme loading.

Endo- and exo-inulinases: enzyme-substrate interaction and rational immobilization.

Three‐dimensional models of exoinulinase from Bacillus stearothermophilus and endoinulinase from Aspergillus niger were built up by means of homology modeling. The crystal structure of exoinulinase from Aspergillus awamori was used as a template, which is the sole structure of inulinase resolved so far. Docking and molecular dynamics simulations were performed to investigate the differences between the two inulinases in terms of substrate selectivity. The analysis of the structural differences between the two inulinases provided the basis for the explanation of their different regio‐selectivity and for the understanding of enzyme‐substrate interactions. Surface analysis was performed to point out structural features that can affect the efficiency of enzymes also after immobilization. The computational analysis of the three‐dimensional models proved to be an effective tool for acquiring information and allowed to formulate an optimal immobilized biocatalyst even more active that the native one, thus enabling the full exploitation of the catalytic potential of these enzymes.

Experimental study on integrated membrane processes in the treatment of solutions simulating textile effluents. Energy and exergy analysis

Abstract Membrane processes in the textile industry can minimize pollution phenomena contributing also to decrease energy consumption, to increase product quality and improve the overall process efficiency. In this study the energy consumption of simulated textile processes have been analyzed and compared with systems where membrane technologies have been introduced. The value of dye and salt concentration which might be reached have been tested in a reverse osmosis pilot plant. The hydrodynamic characteristics of the spiral wound modules used and evaluation of their efficiency in terms of rejection, fluxes and life time of the membranes are reported. The possibility of reaching higher concentration of chemicals by membrane distillation, using the concentrate of reverse osmosis as feed, has also been studied. Based on experimental results, an energy and exergy analysis was attempted. Substitution factors, related to the electrical energy consumption in reverse osmosis and in an integrated reverse osmosis — membrane distillation process have been calculated and compared to cycles with chemical recovery and without recovery.

Optimization of ricotta cheese whey (RCW) fermentation by response surface methodology.

A central composite design (CCD) was performed to evaluate the effects of four factors, i.e. temperature (T), pH, agitation rate (K) and initial lactose concentration (L), on ricotta cheese whey batch fermentation and to optimize the process leading to the formation of bio-ethanol. Anaerobic batch fermentation experiments were carried out by using the yeast Kluyveromyces marxianus. After a preliminary experimental analysis, the values of the chosen factors were 32 and 40 degrees C for T, 4 and 6 for pH, 100 and 300 rpm for K, 40 and 80 g L(-1) for L. Response surface methodology (RSM) was used to optimize the fermentation process and an empirical polynomial model was used to fit the experimental data. The best operating conditions resulted to be T=32.35 degrees C, pH 5.41, K=195.56 rpm and L=40 g L(-1) and the model ensured a good fitting of the observed data.

A hybrid neural approach to model batch fermentation of “ricotta cheese whey” to ethanol

Abstract In this work, the fermentation of “ricotta cheese whey” for the production of ethanol was simulated by means of a multiple hybrid neural model (HNM), obtained by coupling neural network approach to mass balance equations for lactose (substrate), ethanol (product) and biomass. A HNM represents an alternative method that may allow predicting the behaviour of complex systems, such as biotechnological processes, in a more efficient way. Some well-assessed phenomena, in fact, are described by a fundamental theoretical approach; some others, being very difficult to interpret, are analysed by means of rather simple “cause–effect” models, based on artificial neural networks. The experimental data, necessary to develop the model, were collected during batch fermentation runs. For all the proposed networks, the inputs were chosen as the operating variables with the highest influence on reaction rate. Simulation results showed the ability of the developed model to represent the process dynamics. The HNM was capable of an accurate representation of the system behaviour by predicting biomass, lactose and ethanol concentration profiles with an average error percentage lower than 10%. Moreover, the hybrid approach showed the ability to limit error propagation into the models that can be caused by the purely black-box nature, typical of neural networks.