The present work examined the production of single-cell protein (SCP) by a newly isolated strain of Kluyveromyces marxianus EXF-5288 under increased lactose concentration of deproteinized cheese whey (DCW) and different temperatures (in °C: 20.0, 25.0, 30.0 and 35.0). To the best of the authors’ knowledge, this is the first report examining the ability of Kluyveromyces marxianus species to produce SCP at T = 20.0 °C. Different culture temperatures led to significant differences in the strain’s growth, while maximum biomass and SCP production (14.24 ± 0.70 and 6.14 ± 0.66 g/L, respectively) were observed in the cultivation of K. marxianus strain EXF-5288 in shake-flask cultures at T = 20.0 °C. Increased DCW lactose concentrations (35.0–100.0 g/L) led to increased ethanol production (Eth_max = 35.5 ± 0.2 g/L), suggesting that K. marxianus strain EXF-5288 is “Crabtree-positive”. Batch-bioreactor trials shifted the strain’s metabolism to alcoholic fermentation, favoring ethanol production. Surprisingly, K. marxianus strain EXF-5288 was able to catabolize the produced ethanol under limited carbon presence in the medium. The dominant amino acids in SCP were glutamate (15.5 mg/g), aspartic acid (12.0 mg/g) and valine (9.5 mg/g), representing a balanced nutritional profile

The production of value-added products from microorganisms, such as single-cell protein (SCP), through the valorization of agricultural byproducts enhances circular economy while offering alternative solutions for waste treatment. In this study, SCP was obtained through the biotechnological treatment and valorization of cheese whey, the main byproduct of the dairy industry, for the development of novel edible films. To the best of the authors’ knowledge, this is the first report examining SCP as a biopolymer for edible film production. Specifically, Kluyveromyces marxianus, which has gained QPS and GRAS status, strain EXF-5288 cultivated in deproteinized cheese whey (DCW) lactose (10.0 g/L) in a 3 L fed-batch bioreactor, resulting in a SCP_max of 2.63 g/L with a protein content of up to 49.1% w/w. The addition of increased glycerol concentrations (30, 40, and 50% w/w of dry cells) as plasticizers was examined to develop SCP-based edible films. Regarding physicochemical characterization, increased glycerol concentration significantly increased moisture content (MC%) and solubility (S%), but there was not a significant difference in other parameters. Regarding wettability, SCP-based films could be described as oleophilic surfaces since the degree of oil contact angle (OCA) ranged between 46.7° ± 1.3 and 54.0° ± 0.5. The proposed holistic approach could contribute to the development of sustainable packaging materials through waste treatment.

In recent years, there has been an increase in the industrial processing of shrimp, aiming to cover the increasing demand for shrimp products for human consumption, and, consequently, an increase in shrimp by-products as shrimp waste. This waste includes the cephalothoraxes, heads, shells, tails, pleopods, and exoskeleton appendages of processed shrimps. The appropriate method for the enzymatic hydrolysis of shrimp waste can recover its bioactive substances, including carotenoids. Thus, these xanthophylls and carotenes are of high financial interest and have high antioxidant, anti-inflammatory, and anti-cancer activities. Therefore, these substances can be incorporated into fish feed as ingredients that improve fish health and simultaneously lead to the production of aquaculture fishes similar in coloration to the wild ones. Thus, the consumption of such novel food acts as a preventive factor for human health. In this regard, β-carotene has antioxidant and fat-soluble activities owing to vitamin A sufficiency and has an anti-cancer effect, too. Canthaxanthin can be used as a product for personal care and as a natural tanning agent for human skin. Zeaxanthin and lutein have positive effects on various eye and heart diseases, neuronal damage, human skin diseases, and certain types of cancer. Astaxanthin also has anti-diabetic and anti-obesity properties. Therefore, the purpose of this review is to highlight the sustainable utilization of shrimp waste via enzymatic hydrolysis, the benefits of a fish diet enriched with astaxanthin, the consumption of fish enriched with carotenoids, and the effects of carotenoids on human health. The problem of shrimp waste disposal affects the environment, does not contribute to sustainable development, and is directly related to the phenomenon of environmental change.

Every year, large amounts of shrimp waste are disposed of in the environment, causing serious environmental problems. The prospect of recycling shrimp waste helps to reduce waste and protect the environment. In this study, three different shrimp species were used, including Pleoticus muellieri, Litopeneus vanamei, and Parapenaeus longirostris, separated into shells (PLMUS, LIVAS, PALOS) and tails (PLMUT, LIVAT, PALOT), and transformed into novel carbonaceous materials. Their adsorption properties were investigated using different chemical compounds (MB, MR, phenol, astaxanthin) in aqueous means. The materials were characterized through FTIR, BET, and SEM–EDS analyses. According to the results, the carbonaceous adsorbents presented high adsorption percentage of MB and astaxanthin (>90%), and low adsorption percentage of phenol and MR, owing to the different bonds that were formed between the functional groups of the organic substances and the corresponding groups on the surface of the materials. The results of the FTIR analysis show the presence of C=C groups from the aromatic rings of the adsorbed MB and MR at 1636 cm⁻¹, the presence of O-H functional groups from the adsorbed phenols at 3330 cm⁻¹, and the presence of C=C or C=O groups at 1730 cm⁻¹ after the adsorption of astaxanthin. According to the BET analysis, the increase in the specific surface area follows the order: LIVAS > PLMUS > PALOT > PALOS > PLMUT > LIVAT. SEM–EDS analysis presented compact structures with the main elements of C (37–56%), O (25–35%), and Ca (12–23%) for all materials. Kinetic analysis showed that the experimental adsorption data of all the organic substances can be best described by the pseudo-second order model, indicating that chemisorption is the prevailing mechanism. Consequently, such methods promote the sustainable management and zero-waste fish farming practices, fostering the production of high-added value materials not only for decontamination purposes but also for the isolation of bioactive substances.

Plant mediated synthesis of silver nanoparticles is eco-friendly and of low cost. The synthesis involves a reduction of silver ions and is controlled by several independent factors. In this work, silver nanoparticles (AgNPs) were successfully synthesized using olive stone extract (OSE) and olive mill wastewater (OMW) extract. The nanoparticle synthesis was monitored using the plasmon resonance observed in the UV–Vis absorption spectrum, in which a Voigt profile was fitted. The peak wavelength (λ ₀), the peak area (A), and the Full Width at Half Maximum (FWHM) were the fitting parameters and were used as the response. The independent factors were the incubation temperature, the incubation time, the silver nitrate, extract, and sodium hydroxide concentrations. The influence of these factors was investigated ‘two factor at a time’, using interaction plots. Strong interaction was observed between all factors, with sodium hydroxide to have a crucial role. The optimum conditions for silver nanoparticle formation were a) OSE (1% v/v), AgNO₃ (2 mM), and NaOH (0.2 mM), and b) OMW (2% v/v), AgNO₃ (1 mM), and NaOH (7.9 mM), showing an absorption maximum at 414 nm, and 410 nm, respectively. The mean diameter of AgNPs using OMW, measured with Transmission Electron Microscopy was 12.87 ± 4.84 nm. Both types of AgNPs showed antibacterial action against Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli), using the broth microdilution assay. Both nanoparticle types inhibited bacterial growth up to one dilution higher than reference samples.

Novel sorbents were produced using sustainable and eco-friendly methods, aimed at minimizing environmental impact while utilizing industrial by-products and natural minerals. Olive stones and molasses derived from olive mill and sugar industries, respectively, and an abundant, natural and low-cost mineral, clinoptilolite, were combined in the following proportions: 80/20 clinoptilolite/stone, 80/10/10 clinoptilolite/stone/molasses, 50/50 stone/molasses, w/w. Then, physical carbonization (CL80OL20C, CL80OL10M10C, OL50M50C) or chemical activation (CL80OL20A, CL80OL10M10A, OL50M50A) took place. The adsorbents were characterized through Raman, FT-IR, BET and SEM-EDS analysis. The CL80OL20A material presents the highest ratio of C/O in EDS analysis and the lowest I_D/I_G in Raman spectroscopy. The increase in the specific surface area is as follows: OL50M50C < OL50M50A < CL80OL10M10C < CL80OL20C < CL80OL20A < CL80OL10M10A. Three applications were conducted: two with dyes (methylene blue and methyl red) in aqueous means and one in olive mill wastewaters for the removal of total phenols and their addition to rice, increasing the total phenolic content and producing novel foods. The well-fitted application of the pseudo-second order kinetic model to the experimental data has shown that chemisorption is the prevailing mechanism. The adsorbed amount of the recovered phenols to rice ranges from 0.14 to 0.93 mg/g. Consequently, olive and sugar by-products can be used as filters either to adsorb dangerous organic compounds or to recover bioactive compounds from wastewater, preventing their disposal in the environment, which could otherwise lead to severe negative effects on the ecosystems.