Development of semi-theoretical light radiation and photosynthetic growth model for the optimal exploitation of wastewaters by microalgae

In the last decade, interest toward the potential application of microalgae has grown considering their potential use in industrial sectors as human nutrition and health, animal feed and biopolymers. Their ability to use light or/and organic carbon as energy source, makes them able to grow in a wide range of conditions. Because of that, the possibility to use alternative nutrients and water sources for their cultivation has been investigated. The microalgal cultivation using wastewaters mixed with synthetic medium might be a good combination that could reduce costs of water, nutrients and wastewater treatment. Anyway, wastewaters are frequently dark colored and contain toxic compounds that could have a negative impact on microalgal light uptake and metabolism. In this study, an experimental first principles hybrid method for the estimation of microalgal growth in non-transparent media was developed as a guide in the choice of the best formulation of wastewater-based culture media for microalgae. To carry out several experimental runs in parallel with different conditions (dilution of the wastewater, different light sources, etc.) a cylindrical bubble column PhotoBioReactor (PBR) was adopted. Its simple geometry allows the analysis of inside light fluxes. A non-metabolizable and non-toxic dye, in condition of purely light-radiative growth limitation, was added to the medium mimicking the reduced transparency of wastewaters. As final step to test the model, culture mediums with wastewater addiction were used for microalgal cultivation, showing their nutritive effects on growth

Parametric analysis of the strength in the ''Toronto'' osseous-prosthesis system

AIM: The aim of this work is to analyze how the different distributions of the chewing load could be related to dental prosthesis fractures of the Toronto restoration via the fulfilment of a virtual parametric model. Moreover investigation about implant positions and perspectives in comparison with a virtual medial plane was made to evaluate the incidence of screw and prosthesis breakage. METHODS: Finite element analysis of the lower jaw was performed to underline parameters and mechanical features of dental implants connected with the fractures of the prosthetic restoration. Jaw virtual model and 3D fixtures (Global Sweden and Martina) were created by Cosmos-Solid Works. Matlab was used to recreate the distribution of an unspecific chewing phase analyzing the overall load on the fixtures of the lower jaw. RESULTS: Four virtual 3D models were performed with Matchad 14, for data analysis. The study investigated frontal and horizontal planes and vertical direction of the occlusal forces. Data results showed how position and perspective of fixtures strongly influenced the stress distribution upon the bone of the jaw; safeguard of prostheses elements like cantilever, passing screws, and dental implants are strictly related to a correct selection of the dental implant position. CONCLUSIONS: The 3D geometry of the jaw is an important condition for the choice of position, number, diameter and length of dental implants used for Toronto prostheses. This study would suggest a virtual ''method'' to help the surgeon choosing a correct model for a prosthetic rehabilitation evaluating position, perspective, and stress distribution of the chewing strengths

Circular extraction. An innovative use of switchable solvents for the biomass biorefinery

The environmental impact of biomass processing can best be minimized by utilizing many components of the biomass and by getting maximum utility out of any solvent used. A Switchable-Hydrophilicity Solvent (SHS) has been used for a complete extraction of hydrophobic and hydrophilic molecules in the solvent's opposite-hydrophilicity states, thus simplifying microalgal biomass extraction and increasing the solvent usefulness

Cemented-retained vs screw-retained implant restorations : an investigation on 1939 dental implants

AIM: The aim of this work was to present a comparison of screw-retained and cemented-retained implant prostheses based on a retrospective analysis of 1 939 dental implants. The advantages, disadvantages, and limitations of those two different types of dental restorations are discussed and compared with the recent international literature. It is important to underline the influence of the attachment mechanism on many clinical aspects of implant dentistry. METHODS: A group of 527 patients was analyzed. All of the patients required implant rehabilitation. 1 939 dental implants were positioned between January 1997 and December 2003. RESULTS: The analyzed clinical trials show the presence of several factors essential to the long-term success of any implant prosthesis. Aesthetic, retrievability, passivity of framework, occlusion, ease of fabrication and cost and retention. In this study, 762 cemented dental prostheses were used for 1 551 dental implants placed. The survival rate of this rehabilitation was 98.4 % with an average of 34.7 month follow-up; 84 screwed-dental prostheses were placed on 330 dental implants. The success percentage of this type of prostheses was 100% with an average of 44.3 month follow-up. CONCLUSION: Cemented-implant prosthesis and screw-retained implant prosthesis analyzed in this investigation, present with advantages and disadvantages. Clinicians should be aware of the limitations and disadvantages of each type of prosthesis, so as to select the one that is most appropriate for a given clinical situation

A novel switchable-hydrophilicity, natural deep eutectic solvent (NaDES)-based system for bio-safe biorefinery

A switchable-hydrophilicity solvent system, consisting of a fatty acid-based natural deep eutectic solvent (NaDES), complemented by a bio-friendly dilute amine solution, has been introduced. The potential of the most benign switchable solvent system has been characterised in microalgae biorefining according to the recently proposed ‘Circular Extraction’ scheme

Industrial bio-fractionation process of microalgae valuable products using supercritical {CO}2. A techno-economical evaluation

This work shows how Omega-3 triglycerides and carotenoids can be produced industrially from the microalga Chlorella vulgaris by fractionating extraction employing supercritical CO2, also estimating the relevant costs. One key point is that the devised process separates triglycerides from carotenoids. The estimates have been carried out by modelling both triglycerides and carotenoids extraction and purification, by quantifying the overall process material and heat balance and required operating conditions with the aid of a process simulation spreadsheet. The results showed separate streams of 138.3 kg per day of triglycerides and 8.4 kg per day of carotenoids can be obtained from a daily feed of 360 kg of freeze-dried microalga. In addition, an estimation of Operating Expense (OPEX) and Capital Expenditure (CAPEX) was carried out obtaining, respectively, 1050 k€/y and 3699 k€. The developed integrated process shows, in terms of costs and product quality, a significant improvement respect to previous works, underlying its feasibility for industrial applications

Multi-component extraction process of high added value compounds from microalgae with supercritical CO2: A technical and economic study

In this work a multicomponent extraction process of high added value compounds (principally omega-3 fatty acids and carotenoids) from a microalgal matrix (Chlorella vulgaris), using supercritical CO2, was studied. Chlorella's metabolites were analyzed singularly, not as a pseudocomponent, and their affinities to the solvent were explored. The Simplified Broken and Intact Cell model was implemented in order to represent the extraction yields and to define the best conditions in terms of operative variables, ensuring the preservation of the bioactive and thermolabile properties of the extracted metabolites. Moreover, these conditions were chosen also for keeping carotenoids’ solubility in supercritical CO2 very low, in order to separate them (residue stream) from fatty acids (extract stream) without further purification steps. All of these informations were used to implement a simulation of the process, optimizing the daily cycles and increasing the productivity. As last step, calculations of the energy and utilities’ consumption for the estimation of the Operating Expense (OPEX) and Capital Expenditure (CAPEX), as starter point for a future industrial implementation of the process, were carried out

An optimized separation process of microalgal lipidic products by molecular distillation: Techno-economic analysis

Microalgae are a sustainable rich source of high-added value metabolites, as omega-3 and carotenoids, for their ability to grow and accumulate these compounds also in wastewaters or in seawaters. Molecular distillation is a valid techinque respect to conventional distillation for fractionation of these thermosensitive products without affecting their nutritional and biological values. In this work a fractionation process using molecular distillation for separating fatty acids (in part omega-3) as esters and carotenoids from a microalgal lipidic extract, was designed and optimized. A Response Surface Method (RSM) analysis was carried out in order to find the optimal operative conditions of the molecular distiller in terms of temperature, pressure and purification ability. Furthermore, to complete the process scheme, also the design of the other equipments, including in particular the esterification reactor and the dewatering column, was done. In order to complete the feasibility study of the process, an estimation of the Operating Expense (OPEX) and Capital Expenditure (CAPEX), using the results of the simulations in terms of energy and utilities’ consumption, was done. All of these informations, both technical and economical, will be the basis for future industrial implementations of the designed process