Search Results (33)

Excessive concentrations of carbon dioxide (CO₂) in the atmosphere lead to adverse environmental effects. Biologically assisted processes that rely on organisms such as microalgae (i.e., Chlorella vulgaris) are common in capturing CO₂ from the atmosphere. Microalgae are rich in proteins, vitamins, minerals, and omega-3 fatty acids. Thus, microalgae production serves both health and environmental sectors. Varying light intensity and temperature are shown to influence algae growth. To quantify algae production under different light intensity and temperature conditions, and monitoring or scaling-up of biological reactors, reliable mathematical models are required. In this work, mathematical models that incorporate light intensity and temperature effects on algae growth in batch and continuous bioreactors are developed. Based on the modeling, the growth rate is maximum at T_opt = 25 °C, reaching the value of μ_max = 0.14 day⁻¹. The growth rate exponentially increases until light intensity (I) reaches around 150 ${\displaystyle \frac{\mathsf{\mu }\mathrm{m}\mathrm{o}\mathrm{l}}{{\mathrm{m}}^2\mathrm{s}}}$, which is approximately the optimal light intensity for Chlorella vulgaris. The effect of T on growth rate is found to be more sensitive than light intensity (I) in both batch and continuous reactor systems. When there are too many parameters in models, uncertainties exist and parameter estimation and model predictions become cumbersome. For these reasons analytical solutions to the models are presented in simplified forms and these models are more practical and easier to implement. The novelty of the work is also the presentation of the models in analytical forms. Analytical solutions to the two reactor models (batch and continuous) will help quantify biomass production as a function of time under the varying light intensity and temperature conditions encountered. Full article

Brown macroalgae are a promising substrate for alginate production, yet the conventional acid–alkali route raises environmental and quality concerns due to its high reagent inventory, large saline effluents, and partial depolymerization of the polymer backbone. To address these limitations, we evaluated five extraction strategies on a single Saccharina latissima feedstock: conventional acid–alkali extraction as the reference, enzymatic hydrolysis (HE), extrusion combined with enzymatic hydrolysis (Ex-HE), sonication combined with enzymatic hydrolysis (S-HE), and the sequential combination of extrusion, sonication, and enzymatic hydrolysis (Ex-S-HE). The optimized HE process achieved an alginate yield of 34.08% on dry biomass. This value exceeds the conventional benchmark of 31.08%. Hydrolysis time and biomass loading governed the yield. Enzyme dose showed no significant effect within the studied range. Sonication alone yielded 14.55% under surface-limited kinetics, driven exclusively by acoustic amplitude. Scale-up of HE to a 150 L pilot bioreactor recovered 43% of total soluble solids through lyophilization. Ethanol precipitation at the 5 L scale delivered 26.87% of purified alginate. The two metrics describe distinct end products. They represent complementary outputs of a cascade biorefinery rather than competing routes. The HE-derived alginate matches commercial standards by FTIR, TGA, and viscosity. Its M/G ratio is expected to fall within the published range for S. latissima alginate (1.4 to 1.8). Ethanol precipitation of brown algal hydrolysates typically yields products with 80 to 95% uronic acid content. Quantitative techno-economic and environmental analysis indicates substantial reductions in CO₂-equivalent emissions and E-factor relative to the conventional route. Total cost becomes competitive when the cascade biorefinery is monetized through co-products such as mannitol, laminarin, and phlorotannins. These results position enzymatic hydrolysis as the most effective single-step strategy for alginate recovery from S. latissima. To our knowledge, this is the first study to couple face-centred central composite optimization of two pretreatment families on a single S. latissima biomass batch with a 30-fold pilot-scale validation from 5 L to 150 L and a comparative functional characterization of two recovery methods (ethanol precipitation and lyophilization). Full article

Industries seek microorganisms capable of producing all types of cellulases, using low-cost substrate and under adequate process conditions, especially through submerged fermentation. Pleurotus ostreatus “L123” was evaluated as a potential microorganism for cellulase production, assaying total cellulolytic activity (FPase). Fermentation was carried out using a 14L bioreactor, inoculated with 10% (v/v) grown on potato dextrose broth for 4 days. Fermentation media was composed of defatted rice bran (50 g/L), glucose (5 g/L), corn steep liquor (5 g/L) and chloramphenicol (0.25 g/L). Aeration and agitation effects on enzymatic activity were evaluated using a central composite design (CCD) for FPase after 5 days of fermentation. The obtained model was statistically significant, with the interaction of both parameters also being significant and presenting a negative effect. Membrane ultrafiltration (150 kDa MWCO) led to an approximately 3-fold increase in specific activity of permeate (0.6441 vs. 0.2043 FPU/mg of protein), with retention of around 80% of protein content while maintaining enzymatic activity of permeate similar to unfiltered broth (0.0932 vs. 0.0923 FPU/mL). The maximum value obtained experimentally was 0.1444 FPU/mL, which is significantly lower in comparison to commercially used strains and consequently unfeasible for industrial use at current state. However, after further improvements and optimization, Pleurotus ostreatus “L123” can become an alternative for in situ cellulase production through submerged fermentation. Full article

This study explores the potential of using paper pulp mill sludge (PPMS) as an economical substrate for producing high-value protease enzymes with an indigenous bacterial strain, Bacillus tropicus P4. Isolated directly from PPMS, B. tropicus P4 showed high protease-producing ability, approximately 134 U/mL after 48 h—more than three times the yield of the benchmark strain (B. megaterium). Among various additives tested to boost enzyme production, Tween 80 emerged as the most effective, increasing enzyme activity by more than threefold compared to the control. Scale-up experiments in bioreactors of 5 L and 150 L confirmed that B. tropicus P4 maintains high protease yields under typical cultivation conditions with minimal modifications, specifically the addition of Tween 80 (1%) and increased total solids concentration (25 g/L). In the 5 L bioreactor, enzyme production peaked at approximately 755 U/mL within 24 h, while the 150 L bioreactor consistently achieved high enzyme activity (~848 U/mL). These results support the feasibility of a simple and scalable approach for converting industrial sludge into high-value protease enzymes, contributing to resource recovery and circular bioeconomy strategies. Full article

Water scarcity in Mediterranean regions such as Morocco makes treated wastewater a strategic alternative for irrigation. This field study evaluated the effects of two treated wastewater sources, membrane bioreactor T2 and activated sludge T3, compared with groundwater (T1, control) on growth, yield, and fruit quality of two tomato cultivars (Solanum lycopersicum L., Bobcat and Galilia). Irrigation with activated sludge effluent T3 significantly improved agronomic performance relative to both MBR-treated water and groundwater. Under T3, plant height reached 158 ± 3.5 cm in Galilia and 150 ± 3.2 cm in Bobcat, while fruit yield increased to 9.93 ± 0.38 kg plant⁻¹ in Bobcat and 7.12 ± 0.25 kg plant⁻¹ in Galilia, more than double the yield recorded under T2. Physiological parameters such as chlorophyll a, proline, and soluble sugars increased markedly under T3, indicating enhanced photosynthetic activity and improved stress tolerance. Fruit quality was enhanced under T3, with higher soluble sugar and protein levels, while lycopene and acidity were greatest under groundwater irrigation. Overall, the results demonstrate that secondary treated wastewater, particularly from activated sludge processes, can sustainably improve tomato yield and quality while conserving freshwater resources in arid regions. These findings demonstrate the potential of treated wastewater as a sustainable irrigation source for water-scarce Mediterranean agriculture. Full article

Vanilla (Vanilla planifolia Andrews) cultivation is globally relevant due to the extraction of vanillin from its cured fruits. However, the high demand for propagules for commercial plantations requires new propagation methodologies, including in vitro propagation. Currently, the use of biostimulants in plant micropropagation protocols is being explored to increase the number of plants obtained and their vigor. Nanomaterials such as silicon dioxide nanoparticles (SiNPs) have shown a positive effect on plant growth and development. The objective of this study was to evaluate the effect of SiNPs on the micropropagation of V. planifolia in RITA^® bioreactors. In vitro plants were transferred to Murashige and Skoog (MS) medium supplemented with different concentrations of SiNPs < 50 nm (0, 50, 100, and 150 mg L⁻¹) in RITA^® bioreactors. The obtained plants were then acclimatized in a greenhouse. The results indicated that 150 mg L⁻¹ of SiNPs produced the highest average shoot number, with 5.12 shoots per explant (5.48 cm in length), 9.50 leaves, and 5.00 roots per explant. The formation of an optimal root system in plants with SiNPs allowed for 98% survival. Results will enable more efficient in vitro propagation protocols through the obtainment of plants with greater length and a developed root system that facilitates ex vitro adaptation. Full article

Mesenchymal stem cells are widely cultivated in stirred tank bioreactors. Due to their adhesion properties, they are attached to small spherical spheres called microcarriers. To understand the hydromechanical stresses encountered by the cells, it is essential to characterize the flow using the PIV technique. However, the usual solid–liquid system used in cell cultures has poor optical properties. Thus, shifting to one with better optical properties, while respecting the physical characteristics, is mandatory to achieve a relevant representation. PMMA microparticles suspended with 61 wt% ammonium thiocyanate solution NH₄SCN were found to be a robust candidate. The refractive index (RI) of both sides is of the order of 1.491 with a density ratio of ${\rho }_f/{\rho }_p\approx$ 0.96, and particle size averaged around 168 μm. Using the RIM-PIV (refractive index matched particle image velocimetry) technique for a 0.7 L volume stirred tank equipped with an HTPG down-pumping axial impeller and operating at full homogeneous speed $N=150$ rpm, mean and turbulence quantities of the liquid phase were measured as a function of PMMA particle volume fractions ${\alpha }_p$, which ranged from 0.5 to 3 v%. This corresponds to a particle number density of $n=12$ particles/mm³, which is considered original and challenging for the PIV technique. At 3 v%, the addition of particles dampened the turbulent kinetic energy (TKE) of the liquid phase locally by 20% near the impeller. This impact became trivial (<10%) at the local-average level. The structure and direction of the recirculation loop also shifted. Full article

Microbial proteins offer a sustainable alternative for animal nutrition. Rossellomorea marisflavi NDS, a bacterium isolated from seawater, was previously identified as a promising candidate due to its high protein content. This study aimed to enhance its single cell protein production through systemic fermentation optimization. Single-factor optimization in shake flask determined the optimal conditions to be: a salinity of 20‰ NaCl, a temperature of 32 °C, and an initial pH of 7.3, and a medium composed of 1% (w/v) corn flour, 1% peptone, 0.3% beef extract, and 0.2% KCl. Scaling up to a 10 L bioreactor demonstrated that a two-stage agitation strategy (150 rpm for the first 20 h followed by 180 rpm for the remaining 12 h) enhanced single cell protein yield. Furthermore, allowing the pH to fluctuate freely was more beneficial for protein production than maintaining a constant pH of 7.3 ± 0.02. Under these optimized conditions, the biomass composition (wet weight) was determined to be 2.3767 ± 0.0205% crude ash, 15.6013 ± 0.0082% crude protein, 0.1023 ± 0.0026% crude lipid, and 2.6997 ± 0.0021% carbohydrates. Amino acid analysis revealed a rich profile, with lysine and glutamic acid being the predominant essential and non-essential amino acids, respectively. Fatty acids analysis indicated that C14:1n5 was the most dominant. These findings underscore the potential of R. marisflavi NDS as a high-quality dietary protein supplement and provide a solid foundation for its industrial-scale production. Full article

The sustainable production of healthy structured lipids (SLs) using oils extracted from agro-industry by-products or non-conventional lipid sources is of utmost importance in the framework of a circular bioeconomy, toward a zero-waste goal. In this study, low-calorie triacylglycerols (TAGs) containing a long-chain (L) fatty acid (FA) at position sn-2 and medium-chain (M) FAs at positions sn-1,3 (MLM type SL) were obtained from virgin cold-pressed milk thistle (51.55% linoleic acid; C18:2), grapeseed (66.62% C18:2), and apricot kernel (68.61% oleic acid; C18:1) oils. Lipase-catalyzed acidolysis with capric acid (C10:0) or interesterification with ethyl caprate (C10 Ethyl) in solvent-free media were performed. In batch reactions, immobilized Rhizomucor miehei lipase (Lipozyme RM) was used as a biocatalyst. For all tested oils, new TAG (SL) yields, varying from 61 to 63%, were obtained after 6 h of interesterification. Maximum new TAG yields were reached after 6, 24, and 30 h of acidolysis with grapeseed (64.7%), milk thistle (56.1%), or apricot kernel (69.7%) oils, respectively. Continuous acidolysis and interesterification of grapeseed oil were implemented in a packed-bed bioreactor, catalyzed by immobilized Thermomyces lanuginosus lipase (Lipozyme TL IM). Throughout 150 h of continuous operation, no lipase deactivation was observed, with average SL yields of 79.2% ± 4.1 by interesterification and 61.5% ± 5.91 by acidolysis. Full article

Natural astaxanthin is a bioactive with high antioxidant power, widely suitable for many applications. This study explores the potential of leftover food as a sustainable and low-cost substrate for producing astaxanthin via direct fermentation using Phaffia rhodozyma. The pretreated and characterized raw materials were fermented in a lab-scale bioreactor under optimized process conditions. The entire process (168 h) was monitored in terms of reducing sugar consumption, yield, and productivity of astaxanthin. The implemented experimental plan achieved high astaxanthin yield and producticity, namely, 230 mg·L⁻¹ and ~1.6 mg·L⁻¹·h, which were attained at 150 h, respectively, with a substrate consumption of around 90% for all samples. The natural astaxanthin obtained showed interesting antioxidant activity, exhibiting a radical scavenging activity of more than 65%, which was evaluated with a DPPH assay. This process not only offers a promising solution for leftover food valorization but also provides a sustainable approach to producing bioactive compounds with significant health value, paving the way for further industrial applications in food, pharmaceutical, and cosmetic sectors. Full article

Over the last two decades, the use of bioreactors filled with aged refuse extracted from closed areas of landfills has proven to be a viable alternative for the treatment of different types of wastewater. This study presents the results obtained during the evaluation of aged refuse used as filling material for a downflow bioreactor during the removal of the organic load present in wastewater generated in the wet processing of coffee. The tests were carried out over a period of 120 days, with 15 days to start up and stabilize the bioreactor and 105 days to perform treatability tests. The aged refuse, once extracted, was dried and sifted to a particle size of less than 50 mm. The bioreactor used had a cylindrical geometry (Ø = 0.20 m, and h = 3.40 m), and it was fed with hydraulic loads of 50, 100, and 150 L m⁻³ d⁻¹. The analysis of the data obtained shows that the system studied achieves the removal of 98.3% of the initial organic load when fed with 150 L m⁻³ d⁻¹. This showcases recycling aged refuse as a technically viable alternative to treat the wastewater generated during coffee processing. Also, the evaluated system has the advantage of needing a short period of time to achieve its stabilization, which turns out to be of great value, especially in its possible use in the treatment of residual water generated in the harvest of agricultural products where the period of harvest is very short. Full article

This work aimed to study the effect of Camellia sinensis extract (CSExt) as a particular growth promoter of Lactiplantibacillus plantarum (LP) in batch and continuous production processes. Growth conditions were 1% (v/v) inoculum, pH_C = 6.5, 1% of dissolved oxygen (D.O.), 37 °C, and 150 rpm in a 0.2 L bioreactor using a commercial MRS broth (de Man, Rogosa, and Sharpe) and 1% (v/v) or 10% (v/v) CSExt according to the experimental design. In batch experiments, the maximum specific growth rate and the affinity constant increased with the increase in CSExt. In continuous culture, biomass production increased significantly with the addition of 1% (w/v) CSExt at 0.15 (1/h). Kinetic parameters adjusted were similar to those reported in the literature. Substrate affinity and the specific growth rate increased significantly in the presence of CSExt in batch and continuous cultures. Based on the results, prebiotics from plant extracts may function as growth promoters in specific physiological stages. This is the first report showing the change in kinetic parameters of a probiotic strain growing in crude plant extracts. Full article

Water kefir is a product obtained through the fermentation of sucrose solution, usually with some kind of dried fruit addition, by a combined culture of micro-organisms which are contained within kefir grains. Its popularity is rising because of the simplicity of its preparation and its anti-inflammatory, antioxidant, probiotic, and antibacterial effects. In this research, the water kefir production was studied in 250 mL jars, as well as in a horizontal rotating tubular bioreactor (HRTB). The first part of the research was conducted in smaller-scale (jars), wherein the optimal fruit and fruit portions were determined. These experiments included the addition of dried plums, apricots, raisins, dates, cranberries, papaya, and figs into 150 mL of initial sugar solution. Also, the optimal ratio between dried fruit and sucrose solution (0.2) at the beginning of the bioprocess was determined. The second part of this research was conducted using HRTB. The experiments in the HRTB were carried out by using different operational modes (constant or interval bioreactor rotation). A total of six different bioreactor setups were used, and in all experiments, figs were added at the beginning of the bioprocess (0.2 ratio between dried figs and sucrose solution). On the basis of the obtained results, the interval bioreactor rotation mode proved to be the better HRTB mode for the production of the water kefir, as the yield of the main fermentation products was higher, and their ratios were the most adequate for the quality of water kefir drink. The optimal results were obtained via HRTB setup 3/57 (3 min rotation, 57 min pause within 1 h) and rotation speed of 3 rpm. Furthermore, it is clear that HRTB has great potential for water kefir production due to the fact that HRTB experiments showed shorter fermentation times (at least five times) than water kefir production in jars. Full article

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4–0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) and commercial UF membrane (molecular weight cut-off (MWCO) 150 kDa) (c-150 kDa); (ii) r-UF membrane modified by dip-coating using catechol (CA) and polyethyleneimine (PEI) (mr-UF) and c-20 kDa membrane. Permeability, fouling behavior, and permeate quality were evaluated. Extensive membrane characterization was conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and confocal laser scanning microscopy (CLSM). Permeate quality for r-UF and mr-UF membranes was excellent and comparable to that obtained using commercial membranes under similar conditions. Additionally, r-UF and mr-UF membranes presented a steadier performance time. Additionally, r-UF membrane demonstrated less tendency to be fouled (R_f, m⁻¹) r-UF 7.92 ± 0.57 × 10¹²; mr-UF 9.90 ± 0.14 × 10¹², c-150 kDa 1.56 ± 0.07 × 10¹³ and c-20 kDa 1.25 ± 0.50 × 10¹³. The r-UF membrane showed an excellent antibiofouling character. Therefore, r-UF membranes can be successfully implemented for wastewater treatment in aMBR, being a sustainable and cost-effective alternative to commercial membranes that can contribute to overcome membrane fouling and membrane replacement issues. Full article

Most of the world’s annual production of mannitol is by chemical means, but, due to increasing demand for natural sweeteners, alternative production methods are being sought. The aim of the study was to screen Yarrowia lipolytica yeast strains and select culture conditions for the efficient and selective biosynthesis of mannitol from glycerol. From 21 strains examined in the shake-flask culture for mannitol biosynthesis from glycerol (100 g/L), three strains were selected—S2, S3, and S4—and further evaluated in batch bioreactor cultures with technical and raw glycerol (150 g/L). The best production parameters were observed for strain S3, which additionally was found to be the most resistant to NaCl concentration. Next, strain S3 was examined in batch culture with regard to the initial glycerol concentration (from 50 to 250 g/L). It was found that the substrate concentrations of 50 and 75 g/L resulted in the highest mannitol selectivity, about 70%. The fed-batch culture system proposed in this paper (performed in two variants in which glycerol was dosed in four portions of about 50 or 75 g/L) resulted in increased mannitol production, up to 78.5 g/L. Full article