Search Results (111)

Due to environmental pollution and the depletion of fossil fuels, there is growing interest in the development and use of biofuels as environmentally friendly alternatives. One of the most promising biofuels is biohydrogen, hydrogen produced through sustainable processes using microorganisms such as bacteria and algae. One of the most interesting bacteria for hydrogen production is Ralstonia eutropha H16, known for its ability to produce oxygen-tolerant hydrogenases. These enzymes play a crucial role in biohydrogen metabolism and production. The aim of this work was to determine the optimal conditions (reactor type and synthetic medium composition) for the cultivation of R. eutropha H16. The culture media contained different concentrations of fructose and glycerol (mono- or double-substrate cultivation) and the experiments were carried out in a batch reactor. The initial experiments were carried out with 4 g/L fructose or glycerol in the culture medium at pH 7, T = 30 °C, and 120 rpm. The mathematical model, consisting of the growth kinetics (described by the Monod’s model) and the corresponding mass balances, was proposed. The developed model was validated using two independent experiments with different initial substrate concentrations: 2 g/L glycerol and fructose in one medium and 4 g/L fructose and 1 g/L glycerol in the second. In order to propose the optimal cultivation procedure for future research, the mathematical model simulations were performed for different reactor types (batch, fed-batch, and continuous stirred tank reactors) and different initial substrate concentrations. The most successful experiment was the one with 4 g/L glycerol, where γ_X = 0.485 ± 0.001 g/L of biomass was achieved. Further calculations showed that the most biomass would be produced at higher glycerol concentrations (at γ_G = 6.358 g/L, γ_X = 1.311 g/L should be achieved after 200 h of cultivation) and when using a fed-batch reactor (γ_X = 0.944 g/L after 200 h of cultivation). Full article

The growing energy demand and the need for climate mitigation strategies have spurred interest in the application of CO₂–enhanced oil recovery (CO₂–EOR) and carbon capture, utilization, and storage (CCUS). Furthermore, natural hydrogen (H₂) production and underground hydrogen storage (UHS) in geological media have emerged as promising technologies for cleaner energy and achieving net–zero emissions. However, selecting a suitable geological storage medium is complex, as it depends on the physicochemical and petrophysical characteristics of the host rock. Solubility is a key factor affecting the above–mentioned processes, and it is critical to understand phase distribution and estimating trapping capacities. This paper conducts a succinct review of predictive techniques and present novel simple and non–iterative predictive models for swift and reliable prediction of solubility behaviors in CO₂–brine and H₂–brine systems under varying conditions of pressure, temperature, and salinity (T–P–m salts), which are crucial for many geological and energy–related applications. The proposed models predict CO₂ solubility in CO₂ + H₂O and CO₂ + brine systems containing mixed salts and various single salt systems (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻) under typical geological conditions (273.15–523.15 K, 0–71 MPa), as well as H₂ solubility in H₂ + H₂O and H₂ + brine systems containing NaCl (273.15–630 K, 0–101 MPa). The proposed models are validated against experimental data, with average absolute errors for CO₂ solubility in pure water and brine ranging between 8.19 and 8.80% and for H₂ solubility in pure water and brine between 4.03 and 9.91%, respectively. These results demonstrate that the models can accurately predict solubility over a wide range of conditions while remaining computationally efficient compared to traditional models. Importantly, the proposed models can reproduce abrupt variations in phase composition during phase transitions and account for the influence of different ions on CO₂ solubility. The solubility models accurately capture the salting–out (SO) characteristics of CO₂ and H₂ gas in various types of salt systems which are consistent with previous studies. The simplified solubility models for CO₂ and H₂ presented in this study offer significant advantages over conventional approaches, including computational efficiency and accuracy across a wide range of geological conditions. The explicit, derivative–continuous nature of these models eliminates the need for iterative algorithms, making them suitable for integration into large–scale multiphase flow simulations. This work contributes to the field by offering reliable tools for modeling solubility in various subsurface energy and environmental–related applications, facilitating their application in energy transition strategies aimed at reducing carbon emissions. Full article

The lingonberry (Vaccinium vitis-idaea L.), recognized for its nutritional value and adaptability to cold climates, faces cultivation challenges, particularly in soil pH and fertility optimization. In a greenhouse study, lingonberry transplants were grown in media with pH levels of 6.5 (3:1:1 PRO-MIX BX/peat moss/perlite) and 5.2 (2:1 peat moss/perlite). Seven months post-exposure to different media pH, various fertility treatments (NPK) were tested, including a control (0–0–0), a balanced 5–5–5 kg ha⁻¹ rate, a standard 36–24–48 kg ha⁻¹ rate, and both higher (up to 54–36–72 kg ha⁻¹) and lower (down to 9–6–12 kg ha⁻¹) rates, applied every three weeks for fifteen weeks across six replications with a standard micronutrient rate. Results showed that media pH significantly affected plant height and volume, with plants at pH 6.5 growing 27% taller and larger than plants at pH 5.2. Fertility levels influenced plant volume, peaking at a moderate fertility rate (18–12–24 kg ha⁻¹) before declining at higher rates. Interactions between pH and fertility significantly impacted shoot biomass, where higher fertility rates (above 36–24–48 kg ha⁻¹) had a more pronounced negative effect on shoot biomass at pH 6.5 compared to pH 5.2. Root dry biomass was consistently 1.2–2.3 times greater than shoot dry biomass and less influenced by the treatments. Shoot death rates increased sharply at fertility rates above 18–12–24 kg ha⁻¹, peaking at 21–35%. Nitrogen concentration in shoots and roots increased with higher fertilizer rates, peaking at 1.74% in the 45–30–60 kg ha⁻¹ treatment. Fertility treatments raised growing media’s electrical conductivity (EC, 1:20 ratio), with a maximum of 1.41 dS m⁻¹ in the 54–36–72 kg ha⁻¹ treatment, though pH remained unchanged. Growing media nitrate levels increased with higher N rates, while ammonium levels were unaffected. Shoot death rates rose significantly with higher nitrate concentrations, particularly above 17.5 mg L⁻¹, but showed no link to ammonium levels. Lingonberries can survive and thrive across a wide range of pH levels. These results indicate that lingonberries are resilient and low maintenance, requiring modest nutrient levels, and excessive fertilization hampers their growth. Full article

Biochar has been promoted mostly as a soil supplement that improves plant growth/yield and to a lesser extent as a growing medium component. The alarmed situation for peat substitution in growing medium renders biochar as a promising substitute for current research. In this study, biochar derived by wood-based materials was evaluated at different ratios (0, 5, 10, 15, and 20% v/v) for peat partial substitution for Antirrhinum majus pot production. Biochar had increased potassium content and pH, which affected the growing media properties (total pores space and water filled capacity) and decreased nitrogen and phosphorus content in the media. Adding ≥15% biochar increased plant height and decreased flowering, but no effect was observed on plant biomass produced. The presence of biochar increased the total phenols and flavanols content and antioxidant capacity, with greater effects at the higher biochar rates used. This resulted in lipid peroxidation and an increase in hydrogen peroxide content, causing oxidative stress. Potassium and magnesium accumulated more but nitrogen and phosphorus were accumulated less in snapdragon leaves. Biochar at 10% can be considered as a successful candidate to partially substitute peat, and efforts to improve growing media characteristics are required for A. majus pot production. Full article

A peat substrate is made from peat from drained peatlands, which is a limited resource. A realistic estimate is that 50% of the world’s wetlands have been lost. Peat is used in horticulture, especially for the cultivation of vegetables in greenhouses. The consequences of peatland exploitation are an increase in the greenhouse effect and a decrease in carbon stocks. Wood fiber can be used as an alternative to peat. The chemical properties of growing media interact and change continuously due to the small volume of growing media, which is limited by the growing container. This study aims to gain new knowledge on the impact of nutrient changes in the microbial degradation of carbon compounds in wood fiber and mixtures with a peat substrate on the content and uptake of nutrients required by plants. The cucumber (Cucumis sativus L.) variety ‘Dirigent H’ developed in the Netherlands was cultivated in growing media of a peat substrate and wood fiber: (1) peat substrate (PS); (2) wood fiber (WF); (3) wood fiber and peat substrate 50/50 v/v (WF/PS 50/50); (4) wood fiber and peat substrate 25/75 v/v (WF/PS 25/75). The rates of fertilization were the following: (1) conventional fertilization (CF); (2) 13 g N per plant (N₁₃); (3) 23 g N per plant (N₂₃); (4) 30 g N per plant (N₃₀). The experiment was carried out with three replications. As the amount of wood fiber increased, the humidity and pH of the growing media increased. The fertilization of the cucumbers with different quantities of nitrogen influenced the nutrient uptake. The plants grown in the 50/50 and 25/75 growing media had the best Cu uptake when fertilized with N₂₃. When the plants grown in the wood fiber media and the 50/50 media were fertilized with N₁₃, N_23, and N₃₀, the Mn content in the growing media at the end of the growing season was significantly lower than the Mn content in the media with conventional fertilization. Thus, nitrogen improved the uptake of Mn by the plants grown not only in the wood fiber, but also in the combinations with a peat substrate. Growing plants in wood fiber and fertilizing them with N₁₃ can result in the optimum uptake of micronutrients. The number and biomass of cucumber fruits per plant were influenced by the amount of wood fiber in the growing media and the application of nitrogen fertilizer. The highest number of fruits and biomass of fruits per plant obtained were significantly higher when the cucumbers were grown in WF/PS 50/50 growing media with additional N₁₃ fertilization. Full article

This study investigated the effects of substrates composed of various ratios of wood fiber and peat (0, 25, 50, 75, and 100% peat (v/v)) mixed with different amounts of lime (0, 2, 4, 6, and 8 g L⁻¹) and start fertilizer (0, 2, and 4 g L⁻¹ Multimix) on the growth and biomass accumulation of petunia (Petunia x hybrida Vilm ‘Finity F1 Purple’) and basil (Ocimum basilicum L. ‘Marian’) in an ebb-and-flow greenhouse system. Growth parameters included plant height, weight, canopy diameter, and chlorosis symptoms for petunia, along with substrate pH and EC measurements. Petunia showed optimal growth in substrates with higher peat content, while basil produced satisfactory biomass across a pH range of 5–7 regardless of substrate type. Optimal petunia cultivation in 100% wood fiber required a significant dose of start fertilizer without lime. Monitoring pH and EC using pour-through and press methods revealed a pH decrease in substrates with added start fertilizer, while substrates with higher wood fiber content were less acidic. Substrates with over 50% (v/v) wood fiber without lime showed a rapid pH increase over five weeks. The pour-through method generally underestimated EC values compared to the press method. These findings contribute to optimizing the wood fiber/peat blends for sustainable horticulture. Full article

Growing resistance to traditional antibiotics poses a global threat to public health. In this regard, modification of known antibiotics, but with limited applications due to side effects, is one of the extremely promising approaches at present. In this study, we proposed the synthesis of novel complex polymeric conjugates of the peptide antibiotic colistin (CT). A biocompatible and water-soluble synthetic glycopolymer, namely, poly(2-deoxy-2-methacrylamido-D-glucose) (PMAG), was used as a polymer carrier. In addition to monoconjugates containing CT linked to PMAG by hydrolyzable and stable bonds, a set of complex conjugates also containing the siderophore deferoxamine (DFOA) and vitamin B12 was developed. The structures of the conjugates were confirmed by ¹H NMR and FTIR-spectroscopy, while the compositions of conjugates were determined by UV–Vis spectrophotometry and HPLC analysis. The buffer media with pH 7.4, corresponding to blood or ileum pH, and 5.2, corresponding to the intestinal pH after ingestion or pH in the focus of inflammation, were used to study the release of CT. The resulting conjugates were examined for cytotoxicity and antimicrobial activity. All conjugates showed less cytotoxicity than free colistin. A Caco-2 cell permeability assay was carried out for complex conjugates to simulate the drug absorption in the intestine. In contrast to free CT, which showed very low permeability through the Caco-2 monolayer, the complex polymeric conjugates of vitamin B12 and CT provided significant transport. The antimicrobial activity of the conjugates depended on the conjugate composition. It was found that conjugates containing CT linked to the polymer by a hydrolyzable bond were found to be more active than conjugates with a non-hydrolyzable bond between CT and PMAG. Conjugates containing DFOA complexed with Fe³⁺ were characterized by enhanced antimicrobial activity against Pseudomonas aeruginosa compared to other conjugates. Full article

Soy molasses, a by-product from the processing of soy protein concentrate, is a low-cost feedstock for fermentation processes due to its high content of fermentable sugars. This work investigates the use of soy molasses for growing Bacillus species, aiming at their potential application as plant growth promoters. Firstly, six Bacillus strains were screened for their ability to grow in increasing concentrations of soy molasses in a microplate assay. Following this, shaken-flask assays for growth and γ-polyglutamic acid (γ-PGA) production by three Bacillus strains in medium E and soy molasses media with 28 and 56 g L⁻¹ of total reducing sugars (TRS) were carried out. An in vivo experiment evaluated the effect of the bacterial fermented broths on the germination and initial development of maize. Soy molasses supported the growth of Bacillus amyloliquefaciens, Bacillus subtilis, and Bacillus licheniformis in concentrations of 28 and 56 g L⁻¹ TRS, but it was inhibitory at 112 and 224 g L⁻¹ TRS. In soy molasses media, growth was not always associated with γ-PGA production, which was a maximum of 56 g L⁻¹ TRS for B. amyloliquefaciens and B. licheniformis. Fermented broths with B. subtilis and B. licheniformis in soy molasses media (56 and 28 g L⁻¹ TRS, respectively) applied to maize seeds resulted in the highest Vigor Indexes of the seedlings, which correlated negatively with the broth pH and were not impacted by the γ-PGA and indole acetic acid produced by the bacteria. The low-cost and easily available feedstock soy molasses constitutes a potential culture medium for the growth of plant growth-promoting bacteria. Full article

Sour beers play an important role in the brewing market, and their production has been growing exponentially. In light of this, six microorganisms directly related to this class of beer were studied, and the fermentation behavior of six strains used in the past for traditional commercial Berliner Weisse beer production was monitored. The microorganisms used were Lactobacillus brevis, Lactobacillus parabrevis, Brettanomyces bruxellensis, and Brettanomyces anomalus and two strains of Saccharomyces cerevisiae. The six microorganisms were selected in a previous work, and a comparison between single and mixed fermentations was carried out via daily measurements of the fermentation parameters like pH, extract, and cell count during 22 days. The ability to isolate a specific microorganism from a mixed culture was investigated using three commonly used nutrient media and aerobic/anaerobic growth conditions. Both Lactobacillus and Brettanomyces could be isolated; however, the conditions imposed were not sufficient in order to isolate Saccharomyces. Fermentations carried out with LAB and Brettanomyces showed a decrease in Lactobacillus growth if compared to pure fermentations, but no influence on the growth of Brettanomyces could be perceived. In general, fermentations carried out in the presence of Saccharomyces were dominated by this yeast. Its quick growth seems to be responsible for the high end pH values observed as well as the decrease in cell growth for both LAB and Brettanomyces. A decrease in the cell viability of Saccharomyces was followed by an increased growth of the other microorganisms involved, possibly meaning that the molecules released through apoptosis are used by both LAB and Brettanomyces as a valuable nutrient source. The volatile compound concentrations of the first group were higher in fermentations with Saccharomyces, whereas esters’ concentration was higher in fermentations carried out only with Brettanomyces and Lactobacillus. Furthermore, understanding how these microorganisms interact during the fermentation process can help brewers better control production and ensure the consistency in the quality of the final product. The end pH values and acidity reached levels acceptable for Berliner Weisse beer. This innovative approach certainly contributes to the evolution and refinement of the art of brewing. Full article

During the last few decades, water pollution has become a growing concern at international level. To date, only a few Candida parapsilosis strains were successfully used in environmental remediation. In the present article, the strain C. parapsilosis CMGB-YT was studied for its ability to assimilate hydrophobic substrates and to produce biosurfactants with antimicrobial activity and positive effects on heavy metal removal from contaminated wastewaters. The strain C. parapsilosis CMGB-YT was grown on yeast peptone (YP) media with 1% n-decane, n-dodecane, n-tetradecane, n-hexadecane, as well as commercial sunflower and olive oils. The production of the biosurfactant was evaluated using the emulsification index (E_24%). The surface properties and emulsifying stability of the biosurfactant were determined. The effect of the biosurfactant on the cell growth of two strains of Rhodotorula mucilaginosa and on their removal capacity of lead (0.032 g/L) and cadmium (0.030 g/L) ions from synthetic wastewater were also studied. The antimicrobial potential of 20 mg/mL and 40 mg/mL biosurfactant was established in the presence of pathogenic Candida krusei strains. C. parapsilosis CMGB-YT assimilated n-hexadecane with good rates over 216 h and produced an anionic glycolipidic biosurfactant with stable E_24% towards long-chain carbon compounds at different temperatures, with an alkaline pH and high salinity (10% NaCl). The biosurfactant reduced the surface tension to 53.58 ± 0.42 mN/m, while the critical micellar concentration (CMC) was reached at 4.2% biosurfactant. The crude biosurfactant (5%) enhanced R. mucilaginosa growth in heavy metal-contaminated wastewater, increased chemical oxygen demand (COD) removal of up to 80%, and improved Cd²⁺ removal by 10%. Additionally, the concentrated biosurfactant effectively prevented Candida krusei biofilm formation. In conclusion, the biosurfactant produced by C. parapsilosis CMGB-YT demonstrates promising potential for the efficient treatment of wastewater contaminated with heavy metals and microbial pathogens. Full article

Processes driving nutrient retention in stormwater green infrastructure (SGI) are not well quantified in water-limited biomes. We examined the role of plant diversity and physiochemistry as drivers of microbial community physiology and soil N dynamics post precipitation pulses in a semi-arid region experiencing drought. We conducted our study in bioswales receiving experimental water additions and a montane meadow intercepting natural rainfall. Pulses of water generally elevated soil moisture and pH, stimulated ecoenzyme activity (EEA), and increased the concentration of organic matter, proteins, and N pools in both bioswale and meadow soils. Microbial community growth was static, and N assimilation into biomass was limited across pulse events. Unvegetated plots had greater soil moisture than vegetated plots at the bioswale site, yet we detected no clear effect of plant diversity on microbial C:N ratios, EEAs, organic matter content, and N pools. Differences in soil N concentrations in bioswales and the meadow were most directly correlated to changes in organic matter content mediated by ecoenzyme expression and the balance of C, N, and P resources available to microbial communities. Our results add to growing evidence that SGI ecological function is largely comparable to neighboring natural vegetated systems, particularly when soil media and water availability are similar. Full article

There is a growing market for craft beverages with unique flavors. This study aimed to obtain a palate-pleasing mead derived from Pichia kudriavzevii 4A as a monoculture. Different culture media were evaluated to compare the fermentation kinetics and final products. The crucial factors in the medium were ~200 mg L⁻¹ of yeast assimilable nitrogen and a pH of 3.5–5.0. A panel of judges favored the mead derived from Pichia kudriavzevii 4A (fermented in a medium with honey initially at 23 °Bx) over a commercial sample produced from Saccharomyces cerevisiae, considering its appearance, fruity and floral flavors (provided by esters, aldehydes, and higher alcohols), and balance between sweetness (given by the 82.91 g L⁻¹ of residual sugars) and alcohol. The present mead had an 8.57% v/v ethanol concentration, was elaborated in 28 days, and reached a maximum biomass growth (2.40 g L⁻¹) on the same fermentation day (6) that the minimum level of pH was reached. The biomass growth yield peaked at 24 and 48 h (~0.049 g g⁻¹), while the ethanol yield peaked at 24 h (1.525 ± 0.332 g g⁻¹), in both cases declining thereafter. The Gompertz model adequately describes the kinetics of sugar consumption and the generation of yeast biomass and ethanol. Pathogenic microorganisms, methanol, lead, and arsenic were absent in the mead. Thus, Pichia kudriavzevii 4A produced a safe and quality mead with probable consumer acceptance. Full article

Green walls are seen as an important architectural element in the design of sustainable cities, helping to make cities ecologically rich, green, and healthy places to live. The use of green walls, which have seen a wide range of applications worldwide, is supported mainly because of their potential in combating climate change, and international standards are being developed for the design, implementation, and monitoring of green wall projects. In this study, the effects of different growing media used in green wall systems on plant area and the increase in green wall performance were evaluated using an indirect monitoring technique. Peat, hazelnut husks, rice hulls and perlite were mixed in different proportions to produce the growing media, and their physical and chemical properties were determined. Western red cedar (Thuja plicata) and boxwood (Buxus sempervirens L.) were used for planting the green wall. To measure the growth of the green wall and the planting area, images were taken and examined after planting and at the end of the growing period. According to the findings of this study, we found that growing media with a high water holding capacity and high organic matter content were more successful in terms of increasing plant area and green wall performance. However, factors such as pH and phosphorus were found to have negative effects on plant growth. In addition, it was determined that the physical and chemical properties of the growing media used in green wall systems are important for the plant area in green wall systems and that a balanced optimization of these properties increases the efficiency of green walls. The results obtained in this study show that the use of indirect monitoring techniques is a fast and effective method for monitoring the development of green wall systems. The appropriate use of this technique could be an effective tool for the standardization of installation and could contribute efficiently to the maintenance of green wall systems. Full article

Nitrogen (N) is the most important nutrient in coffee, with a direct impact on productivity, quality, and sustainability. N uptake by the roots is dominated by ammonium (NH₄⁺) and nitrates (NO₃⁻), along with some organic forms at a lower proportion. From the perspective of mineral fertilizer, the most common N sources are urea, ammonium (AM), ammonium nitrates (AN), and nitrates; an appropriate understanding of the right balance between N forms in coffee nutrition would contribute to more sustainable coffee production through the better N management of this important crop. The aim of this research was to evaluate the influences of different NH₄-N/NO₃-N ratios in coffee from a physiological and agronomical perspective, and their interaction with soil water levels. Over a period of 5 years, three trials were conducted under controlled conditions in a greenhouse with different growing media (quartz sand) and organic soil, with and without water stress, while one trial was conducted under field conditions. N forms and water levels directly influence physiological responses in coffee, including photosynthesis (Ps), chlorophyll content, dry biomass accumulation (DW), nutrient uptake, and productivity. In all of the trials, the plants group in soils with N ratios of 50% NH₄-N/50% NO₃-N, and 25% NH₄-N/75% NO₃-N showed better responses to water stress, as well as a higher Ps, a higher chlorophyll content, a higher N and cation uptake, higher DW accumulation, and higher productivity. The soil pH was significantly influenced by the N forms: the higher the NO₃⁻-N share, the lower the acidification level. The results allow us to conclude that the combination of 50% NH₄-N/50% NO₃-N and 25% NH₄-N/75% NO₃-N N forms in coffee improves the resistance capacity of the coffee to water stress, improves productivity, reduces the soil acidification level, and improves ion balance and nutrient uptake. Full article

The purpose of this work was to explore the feasibility of replacing all or part of peat with composted green waste (CGW) for vinca (Catharanthus roseus (L.) G. Don) and zinnia (Zinnia elegans Jacq.) cultivation. Seven different growing media were prepared as follows (volume/volume): T1, 100% CGW; T2, 80% CGW + 20% peat; T3, 60% CGW + 40% peat; T4, 50% CGW + 50% peat; T5, 40% CGW + 60% peat; T6, 20% CGW + 80% peat; and T7, 100% peat. In the course of the experiment, the physicochemical properties of the seven media were analyzed, and the growth of vinca and zinnia was determined. Studies showed that replacing peat completely or partially with CGW could significantly enhance the nutrient content, bulk density, water-holding capacity, total porosity, aeration porosity, water-holding porosity, organic matter, pH, and electrical conductivity of growing media. In comparison with what observed with T7 (control), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), plant height (HP), root length (RL), flower number (FN), total chlorophyll, and the content of chlorophyll a, chlorophyll b, and carotenoids in the leaves of vinca cultivated under T5 conditions increased by 36%, 34%, 84%, 27%, 34%, 25%, 157%, 62%, 60%, and 33%, respectively; SFW, SDW, RFW, RDW, HP, RL, FN, total chlorophylls, and the content of chlorophyll a, chlorophyll b, and carotenoids in the leaves of zinnia increased by 341%, 296%, 365%, 302%, 206%, 93%, 180%, 56%, 49%, 67%, 110%, respectively. Full article