Search

Photosynthetic microorganisms have received enormous attention due to their fast growth rate, higher photosynthetic efficiency (PE) and productivity, and high carbohydrates content (up to 50% DW). Microalgae and cyanobacteria are the organisms investigated, but some differences should be discussed between them, regarding carbohydrates composition, light utilization, growth rates, and biomass productivity. The common batch method to evaluate growth capabilities is strongly limited by a number of factors, such as the acclimation of preinoculum and a changing biomass concentration over time, which makes it more difficult to explain the results. Conversely, in a continuous system operated at a steady state, biomass production is constant and is well acclimated to the reactor adapting to environmental conditions. In this chapter, a brief comparison between cyanobacteria and microalgae based on composition, productivity, and PE is completed and the effectiveness of the continuous system as a method to exploit these organisms for carbohydrate production.

Biogas production and its upgrading to obtain biomethane for use as a transportation fuel has been receiving increasing attention, particularly in Italy. In this work, three commercially developed technologies (Pressure Water Scrubbing, Hot Potassium Carbonate and Pressure Swing Adsorption) are critically compared. Accurate process simulations were carried out to evaluate and optimize the performances in terms of biomethane (and CO2) purity and recovery, as well as specific energy consumption and operating costs, considering a biogas throughput of 500 Nm3 h−1. Results from process simulation were used to develop a detailed Discounted Cash Flow analysis of the different technologies, taking into account the recent subsidies issued on March 19th, 2018 by the Italian legislation to promote biomethane development. All the three processes here considered are able to recover more than 90% of biomethane, with a purity higher than 98%. The economic analysis revealed that, according to the new incentive mechanism set by the Italian so-called Biomethane Government Decree (Government Decree 19/3/2018) the investment payback time would range between 3 and 6 years and the Net Present Value would be positive, whereas in the absence of any incentive the investment would not be profitable for any of these technologies.

The development of new technologies to increase the production of biofuels without directly competing with food production is a must. Microalgal biomass has recently been highlighted in this regard. In this chapter, the role of this biomass for bioethanol production is discussed within a biorefinery approach, in the view to promote industrial sustainability. Cultivation aimed at accumulating around 50%–60% of carbohydrates in the biomass (dry weight) and the importance of water and nutrient recycling are reviewed. Saccharification of biomass using enzymes or acids is addressed together with alternative operations (such as hydrothermal liquefaction and flash hydrolysis) that aim at recovering additional products (i.e., biocrude). Because the main monosaccharide in microalgal biomass is glucose, high rates of hydrolysis and fermentation are possible, achieving more than 80% of the efficiency as a sum of these two operations. Anaerobic digestion to treat vinasse after distillation and the recycling of CO2 from the ethanolic fermentation and from biogas combustion could increase the process sustainability. Finally, the advantage of using microalgae rather than other sources of biomass in bioethanol production is estimated with reference to the production rate, even though the cultivation costs remain still high.

Curcumin is a poorly water-soluble and fragile compound that, by virtue of its biological activities, has been considered for a variety of therapeutic applications. In this work, a novel process based on supercritical fluid technology has been used for encapsulating curcumin in solid lipid particles (SLP) to yield curcumin formulations with enhanced biopharmaceutical properties. SLP were obtained by a Particles Generated from Gas Saturated Solution technique (PGSS), where [tristearin + soy phosphatidylcholine (PC)]/[dimethylsulfoxide (DMSO) + curcumin] mixtures were processed. The effects of operative conditions were investigated in order to identify the main parameters that affect the biopharmaceutical properties of the final product. Samples with (tristearin + PC)/(DMSO + curcumin) w/w ratios ranging from 65.6:1 to 3:1 were prepared either in the presence or absence of helium and then processed by PGSS. The drug loading yield was found to be between 30 and 87 drug/lipid w/w%. The particles obtained from lipid mixtures with low DMSO feed were homogeneous in size. The formulation prepared with the highest DMSO feed yielded a bimodal particle size distribution with significant aggregation. Interestingly, the use of helium in the preparation of the lipid mixture was found to improve the biopharmaceutical properties of the SLP, namely drug loading and particle dimensional features. The preparation process was not found to degrade curcumin indicating that PGSS can be properly set-up for the preparation of curcumin lipid particles.

One of the main limitations to large-scale production of biofuels derived from microalge is the lower efficiency of sunlight conversion. The maximum theoretical value for photosynthetic efficiency is hardly achieved in real outdoor cultivation systems, mainly due to inefficient light utilization, in addition to photosaturation and photoinhibition phenomena that take place at high irradiances. This work is focused on testing different possibilities aimed at improving the overall photoconversion efficiency of microalgal production in photobioreactors. Two strategies were followed: the first one increases the portion of spectrum available for photosynthesis employing luminescent spectral-converter filters on the photobioreactor surface, the second one integrates microalgae reactors with photovoltaic panels, producing electrical energy together with biomass. Experiments were carried out both in batch and continuous laboratory scale flat-plate photobioreactors, at different light intensities and regimes, with two different species ( Nannochloropsis salina and Scenedesmus obliquus ), measuring the growth rate, pigment content, biomass concentration and photosynthetic efficiency. Results show that spectral-converters do not substantially improve the growth rate, while an integrated PV and PBR system could be a valid way to improve energy conversion performances.

Economical considerations are investigated in this section, with reference to high pressure extraction plants, to the production of polyethylene, and to the precipitation by supercritical antisolvent process. In the first case, comparison with conventional low pressure solvent plants are not included, because of differences in the legal situation within diverse countries, which can result in higher or lower investment and processing costs due to regulations in regard to environmental protection, allowed remaining solvent residue levels, usage of diverse solvents and safety precautions. About the production of polyethylene it is shown that the total costs of the low-pressure process are similar to those of the high pressure one. Finally, the industrial application of a technique based on the precipitation by a supercritical antisolvent is discussed: it can be economically attractive only with high-value products, such as pharmaceutical ones. Anyway, before setting up a high pressure plant, pre-feasibility studies have always to be carried out in order to ascertain which parameters have greater influence on investment and processing cost.

This chapter discusses two relatively new methods for reducing the microbial activity of foods by means of high pressure. Based on the results obtained, each of them seems to be promising. High-pressure treatment (HTP) has already become an alternative method to ultra-high-temperature treatment and it is used nowadays for commercial production. It allows a total microbial inactivation, by operating with a relatively low temperature, and retaining unchanged the delightful tastes and smells of foodstuffs. Nevertheless, the cost of such a process is still high because of the extreme range of operating-pressure values required, and therefore it is not yet economically competitive with the traditional processes. Results obtained for CO 2 treatment seem to be particularly attractive for the development of industrial applications; so far, mainly experiments on microbial suspensions have been carried out and they are successful. However, some questions remain as to the behavior of microorganisms in complex substrates, because it is well known that they are more resistant than in buffered solutions. Another issue to be addressed in this case is the simultaneous effect of CO 2 as an extracting agent, because it could interfere with the quality of the final product.

Publisher Summary A high-pressure circulation-type apparatus is designed and constructed in this chapter to investigate the vapor–liquid equilibria (VLE) of systems containing limonene, linalool, and supercritical carbondioxide (scCO2). The main piece of the equipment is a high-pressure phase equilibrium cell of approximately 100 cm3. The apparatus includes a compressed-air actuated piston-pump that allows circulating one or both phases to bring the vapor and liquid in close contact with each other. This pump, the cell, and all the related valves are placed in a constant-temperature water bath to have and to keep uniformly the desired temperature. VLE data of binary and ternary systems of limonene, linalool, and scCO2 can be determined in the ranges of pressure and temperature of interest for the deterpenation of coldpressed orange oil. The preliminary results obtained for the binaries CO2–linalool and CO2–limonene are compared in the chapter to data already published with acceptable accuracy and well correlated by a modified Soave–Redlich–Kwong (SRK) equation of state.

Publisher Summary The chapter focuses on the hyaluronic acid benzylic ester (HYAFF) polymers. The production of polymeric HYAFF microspheres loaded with the pharmaceutical is currently performed by solvent–emulsion precipitation. The chapter discusses the production of HYAFF particles through a batch supercritical anti-solvent process (SAS) technique. The coprecipitation of drugs within the HYAFF polymer is examined in the chapter. A supercritical CO 2 -based technique is applied to produce a biocompatible polymer in form of microspheres. With the SAS process carried out in a batch mode, the micronic particles of polymer are obtained with a narrow particle size distribution. The experimental apparatus is easy-to-use and the purification of the precipitated solid from the solvent can be achieved by suitably increasing the time for solvent removing. The possibility to obtain a full solvent-free product, controlling in the same time the dimension of particles, is probably the most important feature when pharmaceutical substances are used. In the SAS process, the supercritical fluid (SCF) is used as the antisolvent.

For design, scale-up, optimisation and control of a commercial reactor it is essential to have accurate kinetic data at hand. In the past, hydrogen reactions in the fine chemicals and pharmaceutical production were carried out with powder catalysts and in a batch mode. Due to more economic and environmental constraints, the application of continuous fixed bed reactors will become more important in the future. It is therefore necessary to have a system for finding the optimal catalyst as well as to study the kinetics of the reaction free of mass transfer and other disturbing effects. The reactor system can be used for hydrogenations with and without solvents, or with supercitical CO2 as a solvent. Emphasis will be in particular on the reactor design as such, the control strategies, and the necessary peripherals will be described in detail. The suitability of this system has been extensively tested with the model hydrogenation reaction of methyl-cinnamate in methanol and with an intermediate for the production of vitamins with CO2 as solvent.

The utilization of supercritical fluids for the processing of pharmaceuticals has attracted considerable interest in recent years. The products' purity, the variety of the forms that can be produced, and the mild operating conditions are important features that make the supercritical techniques an important alternative to classical processes in the pharmaceutical field. Supercritical fluids can be used to extract substances from natural products, as solvents or as anti-solvents to micronize drugs and biodegradable polymers, encapsulate drugs in polymeric matrices, the resolve racemic mixtures of pharmacologically active compounds, fractionate mixtures of polymer and proteins, and sterilize bacterial organisms. The most important advantages of the supercritical fluid technique in the application to pharmaceuticals is the high quality of the products in terms of purity, their unique morphology, and the wide range of materials that can be processed. The mild operating conditions can be especially favorable to bio-labile molecules, such as protein- or genetic-material involved in pharmaceutical applications.