Bioconversion of Crop Residues Using Alternative Fermentation-Based Approaches.

Globally, the growing production of food commodities generates significant quantities of agroindustrial residues, most of which are untreated and disposed of as waste through either burning, dumping into the land, or unplanned landfilling, thereby causing environmental pollution, public health problems, and decreased soil organic matter and soil productivity. A literature review has been conducted on the current crop residue biomass valorization, analyzing raw material properties and the potential risks associated with its incorrect or absent management, as well as the major microbial fermentation strategies that are used for converting residual crops into valuable products. Approximately 2445.2 million tons of crop residues are produced worldwide. Microbial fermentation is an efficient way of managing residues that are rich in nutrients (e.g., nitrogen, phosphorus, and potassium) and converting them into single-cell proteins, antibiotics, enzymes, bioalcohols, polysaccharides, fine chemicals, and others, thereby supporting a circular bioeconomy. Although separate saccharification and fermentation (SHF) represent the predominant fermentation strategy, it requires considerable equipment costs and a long process time, which can lead to the formation of contaminations and inhibitors. Alternative conversion strategies, including simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP), can reduce time and production costs, contaminations, and inhibitor formation, and enhance process yields. Nevertheless, combining hydrolysis and fermentation into a single phase results in non-optimal temperature and pH. This review discusses crop residue valorization through fermentation strategies, and provides a 360-degree view of the topic. After investigating the major types of crop residues and the potential environmental risks associated with their incorrect or absent management, it analyzes the key steps in the crop residue bioconversion process, and the most common microorganisms and microbial cultures. In addition, this review reports on various examples of crop residues being converted into industrial products and analyzes the main fermentation strategies (SHF, SSF, SSCF, and CBP), highlighting their strengths and weaknesses. As a matter of fact, fermentation strategies need to be compared for their benefits and disadvantages before being implemented on a large scale. In addition, the properties and availability of the raw materials, investment, and operating costs, the skilled workforce availability, sustainability, and the return on investment all need to be evaluated. Finally, the discussion focus on future outlooks and challenges.

Application of Turbiscan Stability Index for the Preparation of Alumina Photocatalytic Membranes for Dye Removal.

In this work, for the first time, the stability of the TiO2 suspensions used for the photocatalytic membrane preparation was studied by considering the Turbiscan Stability Index (TSI). The use of a stable suspension during the membrane preparation (by the dip-coating method) permitted a better dispersion of the TiO2 nanoparticles into the membrane structure due to a reduction of agglomerates formation. The dip-coating was performed on the macroporous structure (external surface) of the Al2O3 membrane to avoid large reduction of the permeability. In addition, the reduction of the suspension infiltration along the membrane's cross-section allowed us to preserve the separative layer of the modified membrane. The water flux was reduced by about 11% after the dip-coating. The photocatalytic performance of the prepared membranes was evaluated using the methyl orange as a model pollutant. The reusability of the photocatalytic membranes was also demonstrated.

Stability of Film-Forming Dispersions: Affects the Morphology and Optical Properties of Polymeric Films.

Starch-based films are promising alternatives to synthetic films in food packaging. They were widely studied in terms of mechanical and optical properties. In food packaging, optical properties are of great interest because ultra violet (UV-light) protection is strictly required. Nevertheless, the characterization of film-forming dispersions was poorly addressed, especially regarding its correlation with the film produced. In this work, we characterized film-forming dispersions at different compositions of starch and carboxymethyl cellulose (CMC) by Turbiscan. This instrument is based on multiple light scattering and gives significant information about the miscibility of polymers in the dispersed phase. Indeed, it identifies the phenomena of destabilization and phase separation before their visibility to the unaided eye. This work aimed to study whether the homogeneous/inhomogeneous morphology of films could be forecast by the analysis of profiles obtained in the dispersed phase. The films produced were investigated by optical microscopy and absorbance analysis. As the CMC fraction increased, Turbiscan showed reduced phase separation. This implies better miscibility of mixture components and higher gelification degree. The related film was more homogeneous and presented higher UV absorbance. Consequently, film-forming dispersions and optical properties of films are strictly correlated and Turbiscan-based analysis is very useful to investigate the dispersion stability and predict the film quality.

Transmission of SARS-Cov-2 and other enveloped viruses to the environment through protective gear: a brief review.

Over the past two decades, several deadly viral epidemics have emerged, which have placed humanity in danger. Previous investigations have suggested that viral diseases can spread through contaminants or contaminated surfaces. The transmission of viruses via polluted surfaces relies upon their capacity to maintain their infectivity while they are in the environment. Here, a range of materials that are widely used to manufacture personal protective equipment (PPE) are summarized, as these offer effective disinfection solutions and are the environmental variables that influence virus survival. Infection modes and prevention as well as disinfection and PPE disposal strategies are discussed. A coronavirus-like enveloped virus can live in the environment after being discharged from a host organism until it infects another healthy individual. Transmission of enveloped viruses such as SARS-CoV-2 can occur even without direct contact, although detailed knowledge of airborne routes and other indirect transmission paths is still lacking. Ground transmission of viruses is also possible via wastewater discharges. While enveloped viruses can contaminate potable water and wastewater through human excretions such as feces and droplets, careless PPE disposal can also lead to their transmission into our environment. This paper also highlights the possibility that viruses can be transmitted into the environment from PPE kits used by healthcare and emergency service personnel. A simulation-based approach was developed to understand the transport mechanism for coronavirus and similar enveloped viruses in the environment through porous media, and preliminary results from this model are presented here. Those results indicate that viruses can move through porous soil and eventually contaminate groundwater. This paper therefore underlines the importance of proper PPE disposal by healthcare workers in the Mediterranean region and around the world.

The Influence of Ultrafiltration of Citrus limon L. Burm. cv Femminello Comune Juice on Its Chemical Composition and Antioxidant and Hypoglycemic Properties.

Membrane separation has brought about a significant change in the food processing industry because it could operate separation at low temperature without a reduction of nutrients and bioactive compounds. Citrus limon L. Burm. cv Femminello comune juice, an Italian IGP (Protected Geographical Indication) product, was subjected to the ultrafiltation (UF) process using a cellulose acetate membrane, with a cut-off of 100 kDa, subjected to different transmembrane pressures (TMP, 05⁻1.5 bar). Untreated and ultra-filtrated (UF) juices were investigated for physicochemical parameters including pH, titratable acidity (TA), total soluble solids (TSS) and ascorbic acid content. Total phenols (TPC) and flavonoids (TFC) contents were also determined. Rutin, hesperidin, eriocitrin, and neohesperidin were selected as markers and quantified by HPLC. Antioxidant potential was investigated by using DPPH, ABTS, and FRAP tests. RACI was used to identify the sample with highest antioxidant potential. The hypoglycemic activity was examined using carbohydrates hydrolyzing enzymes assay. The application of increasing pressures across the membrane led to a reduction in TSS without causing a loss of bioactive compounds in terms of TPC and TFC. UF juice obtained with TMP of 1.5 bar (J3) showed a significant amount of eriocitrin and hesperidin with concentrations of 15.8 and 10.5 mg/100 mL, respectively. This sample showed the highest antioxidant potential and exhibited a promising α-amylase and α-glucosidase inhibitory activity with IC50 values of 31.1 and 35.3 mg/mL, respectively. Collectively our results support the use of cellulose acetate membrane to obtain an ultra-filtered juice with significant health potential.

Chemical Profile and Antioxidant Properties of Extracts and Essential Oils from Citrus × limon (L.) Burm. cv. Femminello Comune.

Citrus × limon cv. Femminello Comune (Rutaceae) from Rocca Imperiale (Italy), one of the six Protected Geographical Indication (PGI) Italian lemon crops, has been recently received renewed interest. In this work, fresh and dried peels and leaves were extracted by hydrodistillation, supercritical fluid extraction (SFE), and Soxhlet apparatus. Chemical profile was assessed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Except for leaves extracts obtained by Soxhlet apparatus, the monoterpene hydrocarbons fraction dominated. Limonene, γ-terpinene, and ß-pinene were the main identified compounds. The antioxidant activity was investigated using different in vitro assays namely 2,2-diphenyl-1-picrylhydrazyl (DPPH), ABTS, ferric reducing ability power (FRAP), and ß-carotene bleaching test. In DPPH test, the essential oil obtained by hydrodistillation of fresh peel exhibited the highest activity (IC50 of 1.17 mg/ml). Leaves extracted by SFE showed a good activity in both DPPH and ß-carotene bleaching test with IC50 values of 2.20 and 6.66 mg/ml, respectively. Monoterpene hydrocarbons fraction exhibited a positive Pearson's correlation coefficient with all antioxidant assays. Leaves, often considered waste material, should be considered from a different point because they represent a matrix of indisputable interest.

Neural and hybrid modeling: an alternative route to efficiently predict the behavior of biotechnological processes aimed at biofuels obtainment.

The present paper was aimed at showing that advanced modeling techniques, based either on artificial neural networks or on hybrid systems, might efficiently predict the behavior of two biotechnological processes designed for the obtainment of second-generation biofuels from waste biomasses. In particular, the enzymatic transesterification of waste-oil glycerides, the key step for the obtainment of biodiesel, and the anaerobic digestion of agroindustry wastes to produce biogas were modeled. It was proved that the proposed modeling approaches provided very accurate predictions of systems behavior. Both neural network and hybrid modeling definitely represented a valid alternative to traditional theoretical models, especially when comprehensive knowledge of the metabolic pathways, of the true kinetic mechanisms, and of the transport phenomena involved in biotechnological processes was difficult to be achieved.

Stochastic model-assisted development of efficient low-dose viral transduction in microfluidics.

Adenoviruses are commonly used in vitro as gene transfer vectors in multiple applications. Nevertheless, issues such as low infection efficiency and toxicity effects on host cells have not been resolved yet. This work aims at developing a new versatile tool to enhance the expression of transduced genes while working at low viral doses in a sequential manner. We developed a microfluidic platform with automatically controlled sequential perfusion stages, which includes 10 independent channels. In addition, we built a stochastic mathematical model, accounting for the discrete nature of cells and viruses, to predict not only the percentage of infected cells, but also the associated infecting-virus distribution in the cell population. Microfluidic system and mathematical model were coupled to define an efficient experimental strategy. We used human foreskin fibroblasts, infected by replication-incompetent adenoviruses carrying EGFP gene, as the testing system. Cell characterization was performed through fluorescence microscopy, followed by image analysis. We explored the effect of different aspects: perfusion, multiplicity of infection, and temporal patterns of infection. We demonstrated feasibility of performing efficient viral transduction at low doses, by repeated pulses of cell-virus contact. This procedure also enhanced the exogenous gene expression in the sequential microfluidic infection system compared to a single infection at a higher, nontoxic, viral dose.

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.

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.

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.

Kinetics of enzymatic trans-esterification of glycerides for biodiesel production.

In this paper, the reaction of enzymatic trans-esterification of glycerides with ethanol in a reaction medium containing hexane at a temperature of 37 degrees C has been studied. The enzyme was Lipase from Mucor miehei, immobilized on ionic exchange resin, aimed at achieving high catalytic specific surface and recovering, regenerating and reusing the biocatalyst. A kinetic analysis has been carried out to identify the reaction path; the rate equation and kinetic parameters have been also calculated. The kinetic model has been validated by comparison between predicted and experimental results. Mass transport resistances estimation was undertaken in order to verify that the kinetics found was intrinsic. Model potentialities in terms of reactors design and optimization are also shown.

The state of the art in the production of fructose from inulin enzymatic hydrolysis.

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.