Search Results (539)

Kefiran, the extracellular polysaccharide produced by Generally Recognized as Safe (GRAS) bacteria found in kefir grains, is a promising biopolymer with multiple applications in agri-food and biomedical fields. Besides its characteristics and potential applications, the factors that affect its production remain a prime subject of interest. Lactic acid bacteria synthesize polysaccharides to protect their cells from adverse conditions. Therefore, low-temperature storage (4 °C) of kefir grains inoculated into Ultra-High-Temperature (UHT) milk at two different concentrations (5% and 30%) was studied as a factor for increasing kefiran production in the medium. The cryoprotectant disaccharide trehalose, which comprises a carbon and energy source for many microorganisms, was also evaluated for its effectiveness in enhancing kefiran production. The pH, the increase in kefir grain mass, the amount of kefiran produced, and the rheological properties of the acidified milk were determined during two distinct storage periods, depending on kefir grain concentration. For comparison, kefir grains were also fermented at 25 °C and 30 °C. Low-temperature storage at a kefir grain concentration of 30% resulted in an increase in the amount of polysaccharide produced beyond that obtained through fermentation. Fermentation of a 5% grain inoculum at 30 °C resulted in the lowest kefiran production. In the presence of trehalose, prolonged low-temperature storage favored an increase in the biosynthesis of kefiran, especially at a 30% kefir grain inoculum. Trehalose, however, was not a significant factor in the fermentation experiments. Proper selection of low-temperature storage time is required to avoid a reduction in kefiran concentration due to the metabolic activity of the microorganisms in kefir grains. The acidified milk (low-temperature storage) and kefir (fermentation) samples both exhibited increased elasticity and apparent viscosity with increasing kefir grain concentration. However, the rheological behavior of acidified milk was greatly affected by protein degradation during low-temperature storage. As shown by the findings of the present study, low-temperature storage (4 °C) of a 30% kefir grain inoculum in the presence of trehalose (3% w/w) until a final pH of 4.2 proves to favor kefiran production in the medium the most. Full article

In the summer of 2022, massive blooms of the toxic haptophyte Prymnesium parvum triggered one of the most significant ecological disasters ever recorded in the Odra River, resulting in massive fish and mollusk kills and severe economic damage. Having shown promise for treating other types of phytoplankton blooms, we applied various concentrations of hydrogen peroxide (HP) in an experimental setting using waters collected from the Gliwice Canal; a location with extensive proliferations of P. parvum. In the first stage of our experiment, a single application as low as 14 mg H₂O₂/L successfully reduced P. parvum biomass and prymnesin concentrations, measured using newly obtained prymnesin standards, with limited negative impact on other phytoplankton. In the second stage of the experiment, we reintroduced an inoculum of the canal water containing the haptophyte bloom. The simulated renewal of the phytoplankton community led to higher P. parvum biomass and elevated prymnesin concentrations, possibly due to nutrient release after HP application or reduced phytoplankton competition. We observed differences in the toxin profile compared with control conditions, suggesting changes in the haptophyte ecotypes in the experimental treatments. The results suggest that HP can be successfully used to combat P. parvum blooms, though caution is warranted with higher concentrations. Full article

Plant growth-promoting bacteria (PGPB) could exert positive effects on plant growth and productivity; however, little is known about the effects of variables during the production of PGPB biomass and how they could affect the performances of these microorganisms. This study investigated the effects of pH, temperature, and culture age on the growth of promising PGPBstrains, Bacillus sp. 36M and Stenotrophomonas sp. 20P, isolated from the rhizosphere of durum wheat. A fractional factorial 2^k design was applied to evaluate bacterial growth under varying conditions (pH 5.0–7.5; 15–35 °C; 24–72 h precultures). Multifactorial ANOVA revealed that all independent variables and their interactions significantly affected cell concentration (p < 0.05). Bacillus sp. 36M exhibited optimal growth when inoculated from 24 h cultures and incubated under moderate conditions (15 °C, pH 7.5), whereas Stenotrophomonas sp. 20P showed higher viability with 72 h cultures. These results demonstrate that the inoculum physiological state is a critical determinant of PGPB stress tolerance and should be specifically optimized for each strain. The greater technological robustness of Stenotrophomonas sp. 20P suggests its suitability for biofertilizer formulations requiring extended shelf-life or application under variable environmental conditions. In conclusion, this work provides a quantitative framework for tailoring PGPB production protocols to maximize field performance in sustainable agriculture. Full article

Bacterial resistance in foodborne pathogens is a global concern and has stimulated the search for alternative compounds to antimicrobials. In this context, the prevention of colonization by Salmonella spp. in poultry production is particularly important. This study investigated the bactericidal effect of lysozyme on Salmonella Heidelberg and Salmonella Minnesota. A total of 44 serotyped isolates were subjected to minimum inhibitory concentration (MIC) testing against 17 distinct antibiotics. Subsequently, the same isolates were subjected to minimal bactericidal concentration (MBC) with lysozyme at concentrations ranging from 15 to 2000 ppm. One strain of S. Heidelberg was selected for an in vivo challenge. Seventy-two male chicks were randomly divided into three experimental groups, and two of them were challenged on the second day with 0.5 mL of an inoculum containing 1 × 10⁵ CFU/mL. One of these groups was treated with lysozyme at a concentration of 1000 ppm per bird for 21 days. MIC tests showed that the multidrug resistance rate was 97.72%, with susceptibility only to fosfomycin, florfenicol, and meropenem. After the in vitro exposure of these isolates to lysozyme, 86.36% were inhibited at concentrations ≤ 15 ppm. The in vivo tests showed a significant reduction in the total number of chickens colonized by S. Heidelberg at 2, 5, 7, 14, 18, and 21 days of farming. On the day of slaughter, the percentage of positive birds in the inoculated group was 63.63%, while that in the group treated with lysozyme was 26.08%. These data highlight the potential use of lysozyme as an alternative to antibiotics in poultry production. Full article

The widespread presence of estrogenic pollutants in aquatic environments poses a significant threat to ecosystems and human health, necessitating the development of efficient and sustainable removal technologies. This study aimed to develop a cost-effective biocatalyst for estrogen biodegradation using a fungal laccase. The enzyme was produced by the native strain Dichostereum sordulentum under semi-solid-state fermentation conditions optimized using a statistical Design of Experiments. The design evaluated carbon sources (glucose/glycerol), nitrogen sources (peptone/urea), inoculum size, and Eucalyptus dunnii bark as a solid support/substrate. The resulting laccase was entrapped within a hydrogel made of lignocellulosic biopolymers derived from a second-generation bioethanol by-product. Maximum laccase production was achieved with a high concentration of peptone (12 g/L), a low amount of bark (below 2.8 g), 8.5 g/L glucose and 300 mg/flask of inoculum. The subsequent immobilized laccase achieved 98.8 ± 0.5% removal of ethinylestradiol, outperforming the soluble enzyme. Furthermore, the treatment reduced the estrogenic biological activity by more than 170-fold. These findings demonstrate that the developed biocatalyst not only valorizes an industrial by-product but also represents an effective and sustainable platform for mitigating hazardous estrogenic pollution in water. Full article

Cellulase is an inducible enzyme. By using traditional Chinese medicine residues (TCMRs) as inducer for microbial cellulase, the enzyme’s production yield can be improved. Additionally, this approach enables the resource utilization and harmless treatment of TCMRs. In this study, a fungus that can use TCMRs as a substrate was screened and identified as Penicillium oxalicum. The fungus grew well in the culture medium containing TCMRs, and the highest filter paper activity (FPA) reached 2.06 IU/mL in forsythia leaves residue (FR). After fermentation, the FR exhibited the highest weight loss rate, reaching 22.67%. Enzyme production conditions were optimized using the Plackett–Burman (PB) and Central –Composite Design (CCD) methods. The FPA could reach 2.75 IU/mL under the optimal conditions of FR concentration of 24.84 g/L, (NH₄)₂SO₄ concentration of 2 g/L, temperature of 34.44 °C, pH 6.20, rotational speed of 200 rpm, and inoculum size of 6%, which was 33.50% higher than that before optimization. The crude cellulase was used to extract total flavonoids from TCMRs, and the extraction rate of total flavonoids increased by 24.2–55.1%. The results demonstrated that TCMRs are effective for inducing substrates for cellulase production by Penicillium oxalicum Ti-11. Furthermore, the crude cellulase produced significantly promoted total flavonoids extraction from TCMRs. Full article

Acid mine drainage (AMD), characterized by low pH and high sulfate concentrations, poses severe environmental risks. Sulfate-reducing bacteria (SRB) are promising for AMD bioremediation, but their activity is often inhibited in such extreme conditions. This study proposed two strategies—SRB pre-cultivation and SRB-enhanced sediment amendment—to address this limitation, and systematically examined the effects of sulfate concentration, pH, inoculum size, and carbon source on sulfate removal. Results showed that pre-cultivation significantly improved SRB’s acid tolerance, expanding the effective AMD treatment pH range from 6.8–8.8 to 4.8–8.8. At pH 7.8, pre-cultivated SRB achieved 50% removal of 11,760 mg/L sulfate within 24 h and complete removal within 150 h. The SRB-enhanced sediment system further enabled efficient and stable remediation of real AMD (sulfate removal > 97%, Fe/Mn co-removal > 90%). This work provides a practical solution to overcome SRB inhibition in harsh AMD environments and contributes to the development of low-cost, sustainable AMD bioremediation technologies. Full article

Hydrogen is being increasingly recognized as a promising clean, renewable energy carrier. Among the available production pathways, biological processes, particularly dark fermentation of residual biomasses and agricultural by-products, represent an appealing approach aligned with circular economy principles. These feedstocks are abundant and low cost; however, their relatively low energy density constrains process efficiency. To mitigate this limitation, research efforts have concentrated on optimizing substrate composition and implementing pre-treatment strategies to enhance hydrogen yields. Numerous studies have explored the potential of agricultural and livestock residue, yet reported outcomes are often heterogeneous in terms of units, systems, and experimental conditions, complicating direct comparison. This review consolidates current knowledge and identifies effective strategies to optimize biohydrogen generation. Among the investigated substrates, corn stover emerges as the most promising, with hydrogen yields up to 200 [mL H₂/gVS (Volatile Solids)]. Evidence further suggests that inoculum processing, including enrichment or pre-treatment, can substantially improve performance, often more effectively than substrate processing alone. When both inoculum and substrate are treated, hydrogen yields may increase up to fourfold relative to untreated systems. Overall, integrating suitable feedstocks with targeted processing strategies is crucial to advancing sustainable biohydrogen production. Full article

This study investigated the effect of a concentrated kombucha inoculum and transglutaminase (TG) on the rheological and textural properties of fermented milk products and compared their average production costs to commercial yoghurt. Semi-skimmed milk was used, to which microbial TG was added at a level of 0.02% w/w. The kombucha inoculum, prepared from black tea, was concentrated to 55.6% total solids. Four samples were produced: two with TG and two without. The TG-containing samples showed significantly higher textural properties, including firmness and consistency, than the non-TG samples. They also exhibited the largest hysteresis loop area and the highest yield stress, indicating a stronger gel structure. The Herschel–Bulkley model successfully described the flow behaviour of all samples and confirmed their shear-thinning, non-Newtonian nature. Principal Component Analysis (PCA) showed that both TG addition and inoculum concentration significantly influenced the product properties. TG improved the rheological and textural properties and increased the stability during storage. However, the production costs for TG-treated samples were higher than those for non-TG-treated samples and commercial yoghurt. Nevertheless, the higher costs could be justified by the perceived additional nutritional benefits for consumers. Overall, the results show that the combination of concentrated kombucha inoculum with transglutaminase can improve the structural and rheological quality of fermented dairy products, which is potentially of commercial importance. Full article

The ascomycetous fungus, Zarea fungicola (syn. Lecanicillium fungicola), is the most common fungal pathogen of the white button mushroom, Agaricus bisporus. The objective of this study was to assess the impact of the timing and concentration of spore inoculation on the development of dry bubble disease, its progression, and the yield of mushrooms. Experiments included two factors: inoculation timing (at casing, three days after casing (4th day), onset of induction (7th day), primordia formation (12th day), and mixing spores with casing soil) and different inoculum concentrations (10⁵ m⁻², 10⁶ m⁻², and 10⁷ m⁻² casing). The first symptoms of dry bubble appeared at the beginning of the first flush (14–16 days of cultivation) in trials where spore inoculum was applied three days after casing and during the induction phase. In contrast, the longest disease latent period (26–28 days) occurred when spores were mixed with the casing soil. A significant interaction was observed between inoculation timing and spore concentration, which influenced disease incidence and yield. Area under the disease progress curve (AUDPC) analysis indicated the fastest disease progression following inoculation three days after casing (4th day) and at induction phase (7th day). Correspondingly, the highest reductions in yield and biological efficiency were observed at these inoculation timings. In addition, an increase in conidial concentration generally led to more severe disease symptoms. The results indicate that the period from casing application up to the induction phase requires strict hygiene measures, as infection during this time causes the most significant reduction in yields. Furthermore, the stage of mushroom development and inoculum concentration critically determines the severity of dry bubble, providing important guidance for disease management in white button mushroom cultivation. Full article

This study investigated water quality, metal ion concentrations, and antibiotic residues specifically enrofloxacin (ENR) and its metabolite ciprofloxacin (CIP), across six American shad (Alosa sapidissima) aquaculture sites over a one-year period. Water and sediment samples were analyzed to determine contamination levels, and ENR-degrading bacteria were isolated from the culture environment to explore their potential use in bioremediation. Findings showed that NH₃-N and total suspended solids (TSS) exceeded recommended standards at all sampling sites. Elevated levels of Li, Na (except S1), Fe, Ni (except S2 and S4), Sr, and Cu were found at site S3. Site S5 recorded the highest concentrations of Al, As, and Pb, while Cd was most abundant at S6. In sediments, S5 showed higher levels of Mg, K (except S3), Ca, Cr, Mn, Fe, Ni, As, Pb, Cu, and Zn (except S3). ENR and CIP were detected in all water and sediment samples, with a 100% detection rate. The highest ENR (16.68–3215.95 mg·kg⁻¹) and CIP (3.90–459.60 mg·kg⁻¹) concentrations in water occurred at site S6, following a seasonal pattern of autumn > winter > summer > spring. In sediments, the maximum ENR (41.43–133.67 mg·kg⁻¹) and CIP (12.36–23.71 mg·kg⁻¹) levels were observed in spring. Two ENR-degrading bacterial strains were successfully isolated and identified as Enterococcus and Bacillus. Optimal degradation was achieved at 30 °C, pH 8.0, 6% inoculum, and 3000 Lux, resulting in a 64.2% reduction in ENR after 72 h. Under slightly different conditions (25 °C, pH 10), degradation reached 58.5%. This study provides an efficient strain resource for the bioremediation of ENR pollution in the aquaculture water of American shad. Full article

Background and Objectives: The potential of essential oils (EOs) and fumaric acid (FA) to modulate ruminal fermentation and mitigate greenhouse gas emissions in dairy cows has attracted significant attention. However, little is known about the specific metabolites produced as a result of their interaction. This study investigated the combined effects of essential oil blends (EOBs) and FA on rumen metabolites using a rumen simulation technique (RUSITEC) system. Materials and Methods: Three rumen-cannulated, non-lactating Holstein Friesian cows served as inoculum donors. The total mixed ration (TMR; CON) comprised corn silage (60%), alfalfa hay (20%), and concentrate (20%). Three distinct EOBs were formulated: EOB1 [Garlic, Lemongrass, Cumin, Lavender, and Nutmeg; at 4:2:2:1:1, respectively], EOB2 [Anise, Clove, Oregano, Cedarwood, and Ginger; at 4:2:2:1:1, respectively], and EOB3 [Clove, Anise, Peppermint, and Oregano; at 4:3:2:1, respectively]. Four treatments evaluated were control (CON), EFA1 (EOB1 + FA), EFA2 (EOB2 + FA), and EFA3 (EOB3 + FA). EOBs and FA were included at 10 µL/g feed and 3% of TMR, respectively. Rumen effluents were collected over 5 days for metabolome analysis using liquid chromatography-mass spectrometry (LC–MS). Results: A total of 661 metabolites were detected and identified. Volcano plot analysis revealed 13 differentially abundant metabolites for EFA1, 41 for EFA2, and 19 for EFA3 compared to CON group. PLS-DA analysis showed clear separation of treatments, indicating modifications in the rumen fluid metabolome. Conclusions: The treatments led to the enrichment of pathways involved in amino acid, nucleotide, cofactor, and energy metabolism. These additives have the potential to optimize nutrient utilization and overall animal health. Therefore, in vivo studies should be conducted to validate their efficacy. Full article

Anaerobic digestion (AD) technology is universally acknowledged as the most economically viable and efficient approach for energy recovery from livestock manure. To validate the efficacy of riboflavin-functionalized carbon-based conductive materials (CCM-RF) in enhancing methane production at pilot scale, three pilot-scale upflow anaerobic sludge blanket (UASB) reactors were constructed and separately supplemented with carbon cloth (CC), granular activated carbon (GAC), and a combination of CC and GAC. During reactor initialization, riboflavin and a concentrated inoculum of Methanosarcina barkeri (M. barkeri) were introduced to investigate the mechanistic role of CCM-RF in promoting direct interspecies electron transfer (DIET) and optimizing treatment efficiency during anaerobic digestion of cattle manure wastewater. The results showed that all reactors improved AD performance and maintained stable operation at the OLR of 15.66 ± 1.95 kg COD/(m³·d), with a maximum OLR of 20 kg COD/(m³·d) and the HRT as short as 5 days. Among the configurations, the CC reactor outperformed the others, achieving a methane volumetric yield of 6.42 m³/(m³·d), which represents an eight-fold increase compared to conventional AD systems. Microbial community analysis revealed that, although M. barkeri was initially inoculated in large quantities, Methanothrix—a methanogen with DIET capability—eventually became the dominant species. The enrichment of Methanothrix and the simultaneous enhancement in sludge conductivity collectively verified the mechanistic role of CCM-RF in promoting CO₂-reductive methanogenesis through strengthened DIET pathways. Notably, M. barkeri showed progressive proliferation under conditions of high organic loading rates (OLR) and short hydraulic retention time (HRT). This phenomenon provides a critical theoretical basis for the development of future strategies aimed at the targeted enrichment of Methanosarcina-dominant microbial consortia. Full article

This research determines the techno-economic feasibility of valorizing as biofertilizer the nitrogen (N) and the phosphorus (P) from a municipal wastewater effluent using the microalgae Scenedesmus sp., contributing to phosphorus recycling, resource optimization, and diminishing eutrophication by capturing 74% of N, 97% of P, and 41% of chemical oxygen demand in effluents. The inoculum was conditioned in 20 L photobioreactors by weekly harvesting and refilling at room temperature (25 °C day, 12 °C night) with a 12:12 photoperiod and 4 L/min atmospheric air bubbling. The improved operational conditions were obtained using a Box–Behnken experimental design, establishing that 70% wastewater concentration (vol./vol.), 4.5% nutrient addition, and 3 days’ harvesting time were the best conditions. The estimated biomass production was 176 tons/year, and this represents a maximum net present value of 1.5 MUSD for a 6.8 Ha plant, capturing 10% of municipal wastewater effluent, which serves 64000 inhabitants. The representative operational costs (OPEX) were 32% for utilities, 30% labor costs, and 25% for raw materials, and the required capital expenditures (CAPEX) were 11 MUSD and are related to photobioreactors (64%) and land (21%). The findings demonstrate the potential of microalgae-based systems as a feasible and profitable approach to wastewater valorization, while also highlighting the need for scale-up validation and integration with existing treatment infrastructures, where land requirements and photobioreactor installation will be relevant for financial feasibility. Full article

Postharvest blue mold in apples, caused by Penicillium expansum, leads to fruit decay and patulin (PAT) contamination, incurring major economic and health risks. This study developed a composite biocontrol agent (BCA) by co-cultivating three antagonistic yeasts (Meyerozyma caribbica, Metschnikowia zizyphicola, and Pichia rarassimilans). Mixed-culture conditions and protective additives formulation were optimized via response surface methodology. Optimal biomass production was achieved with a 1:2:3 (v/v/v) yeast ratio in medium containing sucrose (12.49 g/L), yeast extract powder (13.3 g/L), K₂HPO₄ (0.88 g/L), and NaCl (0.95 g/L) under pH 7.0, 1% total inoculum concentration, 24 °C, and a 60 h incubation. The liquid BCA formulation, stabilized with 0.27% gum arabic, 0.49% Tween-80, and 0.079% ascorbic acid, maintained high viability (9.15 log10 CFU/mL after 7 days). In vivo/in vitro trials all demonstrated that the composite BCA rapidly colonized, suppressed P. expansum infection, and significantly delayed pathogen spore germination and hyphal growth. Furthermore, the BCA effectively degraded 10 μg/mL PAT within 24–42 h in various fruit juices with minimal adverse effects on juice quality parameters. Storage at −20 °C preserved the highest bioactivity (7.93 × 10⁸ CFU/mL after 5 months). This optimized composite yeast formulation provides an efficient, eco-friendly strategy for integrated apple postharvest blue mold and PAT detoxification. Full article