Valorization of rice and canned tuna processing wastes: a focus on green extraction techniques

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A short review of green extraction technologies for rice bran oil

Rice is one of the most important crops throughout the world, as it contributes toward satisfying the food demand of much of the global population. It is well-known that rice production generates a considerable number of by-products, among which rice bran deserves particular attention. This by-product is exceptionally rich in nutrients, since it contains a wide spectrum of macronutrients (proteins, fats, carbohydrates) as well as dietary fibers and bioactive compounds. However, rice bran is usually wasted or just used for the production of low-cost products. The lipidic fraction of rice bran contains an unsaponifiable fraction that is rich in such functional components as tocopherols, γ-oryzanol, tocotrienols and phytosterols. This lipidic fraction can be extracted to obtain rice bran oil (RBO), a high value-added product with unique health properties as a result of its high concentration in γ-oryzanol, a powerful antioxidant mixture of bioactive molecules. Conventional extraction methods employ hexane as the solvent, but these methods suffer from some drawbacks linked to the toxicity of hexane for humans and the environment. The aim of the review presented herein is to point out the new green technologies currently applied for the extraction of RBO, by highlighting reliable alternatives to conventional solvent extraction methods that are in line with the twelve principles of green chemistry and a circular economy

Novel insights in dimethyl carbonate-based extraction of polyhydroxybutyrate (PHB)

Background: Plastic plays a crucial role in everyday life of human living, nevertheless it represents an undeniable source of land and water pollution. Polyhydroxybutyrate (PHB) is a bio-based and biodegradable polyester, which can be naturally produced by microorganisms capable of converting and accumulating carbon as intracellular granules. Hence, PHB-producing strains stand out as an alternative source to fossil-derived counterparts. However, the extraction strategy affects the recovery efficiency and the quality of PHB. In this study, PHB was produced by a genetically modified Escherichia coli strain and successively extracted using dimethyl carbonate (DMC) and ethanol as alternative solvent and polishing agent to chloroform and hexane. Eventually, a Life Cycle Assessment (LCA) study was performed for evaluating the environmental and health impact of using DMC. Results: Extraction yield and purity of PHB obtained via DMC, were quantified, and compared with those obtained via chloroform-based extraction. PHB yield values from DMC-based extraction were similar to or higher than those achieved by using chloroform (≥ 67%). To optimize the performance of extraction via DMC, different experimental conditions were tested, varying the biomass state (dry or wet) and the mixing time, in presence or in absence of a paper filter. Among 60, 90, 120 min, the mid-value allowed to achieve high extraction yield, both for dry and wet biomass. Physical and molecular dependence on the biomass state and solvent/antisolvent choice was established. The comparative LCA analysis promoted the application of DMC/ethanol rather than chloroform/hexane, as the best choice in terms of health prevention. However, an elevated impact score was achieved by DMC in the environmentallike categories in contrast with a minor contribution by its counterpart. Conclusion: The multifaceted exploration of DMC-based PHB extraction herein reported extends the knowledge of the variables affecting PHB purification process. This work offers novel and valuable insights into PHB extraction process, including environmental aspects not discussed so far. The findings of our research question the DMC as a green solvent, though also the choice of the antisolvent can influence the impact on the examined categories.This work has been funded by the Horizon 2020 EU Framework Programme: CELBICON project, Grant agreement number: 679050. Open access funding provided by PRIME project funded by the POR FESR 2014/2020 Programme, Asse I – Azione I.1b.2.2 Regione Piemonte, within the Piattaforma Tecnologica per la Bioeconomia.Publicad

Recovery of humic acids from anaerobic sewage sludge: Extraction, characterization and encapsulation in alginate beads

Wastewater production is rising all over the world and one of the most difficult problems is the disposal of sewage sludge (SS). It is known that SS contains certain quantities of added-value compounds, such as humic acids (HA) which in turn have beneficial effects on soil quality and plant growth. On the other hand, SS can retain many pollutants, such as heavy metals. The present work aimed to implement an HA alkaline extraction protocol from anaerobic sewage sludge (ASS). Subsequently, the HA were quantified in ASS, in HA extract and in commercial HA, used as a benchmark, which gave results of 12.53%, 26.87% and 77.87% (on dry matter basis), respectively. FESEM and EDX analyses on lyophilized HA extract confirmed that no heavy metals had passed into the extract. Afterwards, in order to allow controlled release of the HA in soils, alginate beads containing the HA extract were created. Finally, a pot experiment in a greenhouse was performed using Chilean lettuce plants (Lactuca sativa L.) treated with alginate-HA extract beads. At the end of the greenhouse experiments, the hypogean dry biomass of the treated plants was significantly higher than for non-treated plants. The relevance of this study relies not only on the exploitation of green chemistry principles, by converting a waste stream into a high-value product, but also on the application of an approach following a circular economy model

Conventional and ultrasound-assisted extraction of rice bran oil with isopropanol as solvent

After cereal harvesting, rice is subjected to several milling processes to remove hull, germ, and bran and produce the final white rice. The bran represents around 10% of total grain weight and is usually considered as waste material. One of the most common rice bran applications is the extraction of rice bran oil, rich in γ-oryzanol, which has shown many health benefits including antioxidant, anti-inflammatory, and anti-hypercholesterolemic properties. Rice bran oil is usually extracted by organic solvents, which are toxic for health and the environment. In this work, rice bran oil was extracted through isopropanol extraction, and the best-operating temperature and bran to solvent ratio have been identified. After that, an ultrasound-assisted extraction was conducted at room temperature and with the same rice bran to solvent ratio of the isopropanol extraction. The kinetics evaluation through Peleg’s model showed that the solvent extraction reaches the steady-state after 15 min while the ultrasound-assisted extraction reaches the steady-state after only 1 min producing very similar yields in rice bran oil and γ-oryzanol. Comparing these two green extraction techniques through a life cycle assessment, it has emerged that with the same amount of rice bran oil produced, the ultrasound-assisted extraction is the less environmentally impacting process. The room temperature ultrasound-assisted extraction allows minimizing the energy and time consumption demonstrating to be a sustainable process in line with the principles of green chemistry

From tuna viscera to added-value products: A circular approach for fish-waste recovery by green enzymatic hydrolysis

Tuna represents one of the most consumed foods in many parts of the world. It is estimated that about 70 % of the tuna's weight is discarded in the production of canned fillets. This work is focused on the optimization of production of an oil rich in omega-3 from the tuna viscera, provided by a canned tuna production company, using the Alcalase enzyme. Combined use of Design of experiments (DoE), life cycle analysis (LCA), and principal component analysis (PCA) on the collected analytical data made it possible to define the best combination of the values of pH, enzyme/substrate (E/S) ratio, and reaction time, respectively (pH = 8.5), E/S (1 %), and time (120 min), and to better understand the environmental bottleneck of the process. The outcomes of the study demonstrated that the duration of the hydrolysis and the associated electricity consumption is the factor that affects the most the environmental sustainability of the process

Innovative unattended SEM-EDS analysis for asbestos fiber quantification

Scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) is the only affordable analytical technique that can discriminate both morphology and elemental composition of inorganic fibers. SEM-EDS is indeed required to quantify asbestos in confounding natural matrixes (e.g. ophiolites), but is also time-consuming, operator dependent, and strongly relies on the stochastic distribution of the fibers on the filter surface. The balance between analytical time/cost and the method sensibility allows only about 0.5% of the filter to be analyzed, strongly affecting the statistical significance of results. To improve sensitivity and precision and enhance productivity, an unattended quantitative measurement of the asbestos fibers by SEM-EDS is proposed. The method identifies the particle shape first and determines their chemical composition later, saving EDS analytical time. Our approach was tested on four asbestos standards and the relative error on replicated measurements was< 10%. The proposed unattended method quantifies asbestos in natural confounding matrix, also with a very low asbestos content