Gabriele Iorio

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.

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.

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.

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.

Fructose Production by Inulinase Covalently Immobilized on Sepabeads in Batch and Fluidized Bed Bioreactor

The present work is an experimental study of the performance of a recently designed immobilized enzyme: inulinase from Aspergillus sp. covalently immobilized on Sepabeads. The aim of the work is to test the new biocatalyst in conditions of industrial interest and to assess the feasibility of the process in a fluidized bed bioreactor (FBBR). The catalyst was first tested in a batch reactor at standard conditions and in various sets of conditions of interest for the process. Once the response of the catalyst to different operating conditions was tested and the operational stability assessed, one of the sets of conditions tested in batch was chosen for tests in FBBR. Prior to reaction tests, preliminary fluidization tests were realized in order to define an operating range of admissible flow rates. As a result, the FBR was run at different feed flow rates in a closed cycle configuration and its performance was compared to that of the batch system. The FBBR proved to be performing and suitable for scale up to large fructose production.

Monitoring and control of TMP and feed flow rate pulsatile operations during ultrafiltration in a membrane module

The aim of this paper is the presentation of a novel system for continuous monitoring of the operating variables involved in ultrafiltration process. The proposed system is based on the utilization of a data acquisition set, consisting of field point units supplied by National Instruments, connected to a Personal Computer, thus allowing UF module performance monitoring. It is, therefore, possible to continuously measure permeate flux decay and to control membrane fouling by means of a device, controlled by the PC, that is able to generate pulses on both trans-membrane pressure and feed flow rate. This device, already patented by the authors [1], is comprised by a system of electric valves that, during a standard cross-flow operation, prime, without any plant stop or any flux inversion, a “cleansing” procedure for the membrane. The main advantages related to the utilization of this device are: the improvement of both performances and efficiency of membrane cross-flow operations, its simplicity and the economy of its installation, the reduction of the dead times due to plant stops and to traditional cleaning procedures. The application of the proposed system to the BSA ultrafiltration showed a significant increase of permeate fluxes with respect to a traditional cross-flow filtration plant.

Enzyme Membrane Reactors

A growing interest toward the use of purified enzymes as biocatalysts in laboratory scale and industrial applications is being developed as an alternative to more traditional approaches, generally based on fermentation processes.

Preparation of mesoporous materials as a support for the immobilisation of lipase

In this paper the immobilisation of the lipase enzyme on a M41S type mesoporous material support is presented. Different M41S type materials, with a pore diameter ranging from 37to 48 , were synthesised starting from different silica sources, in order to immobilise, by physical adsorption, lipase with a spherical molecular diameter close to 41 . The efficiency of the immobilisation carried out at an optimal pH=7, different temperatures and time, were tested by UV Spectrophotometry. The maximum amount of bound lipase resulted to be around 472 mg at 0°C compared to the 362 mg at 25°C and 119 mg at 40°C. Indeed, the maximun immobilisation efficiency is around 47%. The activity of enzyme immobilised was tested by hydrolysis of triglycerides in olive oil into fatty acids and the lipase immobilised has 78% of the activity of the free enzyme.

An experimental analysis of membrane bioreactor performances with immobilized chymosin

Aim of the present work is the experimental analysis of a continuos flow membrane bioreactor with immobilized chymosin for the hydrolysis of milk k-casein, one of the steps in the cheese production process. Chymosin has been immobilized on the bioreactor membrane by ultrafiltering under pressure its solutions, continuously fed to the system in a total recycle configuration. Bioreactor performances are evaluated in terms of two different parameters: chymosin activity and its release. The former, indirectly, measures the amount of k-casein converted into reaction products ( para-k-casein and GlycoMacroPeptide, GMP); the latter quantifies the amount of biocatalyst that is removed from the membrane by the milk flowing stream. A theoretical approach, based on the boundary layer theory, has also been attempted to estimate the dependence of chymosin release upon the wall shear stress and on the back-diffusion phenomena towards the milk bulk. The experimental analysis of bioreactor behavior has been carried out, searching for the operating conditions and system configurations that maximized chymosin activity and minimized its release. Particular attention has been devoted to the selection of the membrane material: PolySulphone membranes offered the best performance during experiments, as compared to those of PolyPropilene and PolyVinilDeneFluoride. The system configuration that gave best results, both in terms of enzyme activity and of its release, was based on a continuous milk recycle to the bioreactor. Enzyme losses were confined to 5‐10 mg/l range, whereas its activity always attained values high enough (>2 g/l) to promote the coagulation in the next heating step of destabilized milk. During the experiments, an optimal value of the recycle ratio, was also found.