Search Results (188)

This study aimed to systematically optimize the fermentation process for xylanase production by Aspergillus tubingensis FS7Y52, elucidate its enzymatic properties, and evaluate its application potential in the biodegradation of agricultural wastes. Key influencing factors were initially identified through single-factor experiments, followed by the screening of significant factors using the Plackett–Burman design. The optimal values were then approached employing the steepest ascent path method and Response Surface Methodology. The final determined optimal fermentation conditions were: corn husk (20–40 mesh) 40 g/L, tryptone 13.7 g/L, Tween-20 0.75 g/L, pH 6.5, fermentation temperature 42.1 °C, fermentation time 2 days, shaking speed 140 rpm, inoculum size 1 × 10⁷ spores/30 mL, and liquid loading volume 30 mL/250 mL. Under these conditions, xylanase activity reached 115.23 U/mL, representing a significant increase of 90.7% compared to pre-optimization levels. Studies on enzymatic properties revealed that the enzyme exhibited maximum activity at pH 5.0 and 55 °C, and demonstrated good stability within the pH range of 4.5–7.0 and at temperatures below 50 °C. In the degradation of agricultural waste, the enzyme system produced by this strain exhibits significant degradation effects on agricultural waste. A pronounced additive effect exists between xylanase and cellulase. When the dosages were 2430 U/g and 15.7 U/g for xylanase and cellulase, respectively, the maximum reducing sugar release reached 23.3%. The degradation rates of cellulose, hemicellulose, and lignin reached 57.8%, 51.9%, and 55.0%, respectively. Additionally, the strain itself exhibits significant degradation effects on substances such as cellulose in agricultural waste, achieving degradation rates of 78.8%, 70.8%, and 52.5% for cellulose, hemicellulose, and lignin, respectively. This study provides a solid theoretical foundation and technical support for the efficient production of xylanase by A. tubingensis and its industrial application in the resource utilization of agricultural wastes. From an economic perspective, the optimized strategy significantly enhances enzyme production efficiency while reducing substrate consumption and operational costs per unit of enzyme produced. This makes the resulting enzyme mixture more economically viable for large-scale applications. The utilization of this enzyme system to convert tobacco stems into sugars represents a compelling case for agricultural wastes reuse. It transforms residual biomass into high-value products, contributing to a circular bioeconomy by reducing waste and creating new renewable alternatives to conventional products. It provides an economically viable solution for the high-value utilization of woody lignocellulosic biomass. Full article

Inoculated fermentation can enhance the flavor, nutrition, and functionality of juice. The lactic acid bacteria (LAB) are commonly used as starter cultures. This study screened LAB for orange juice fermentation and optimized fermentation factors using response surface methodology (RSM) to improve GABA content in orange juice. A total of 52 LAB strains were screened, and Lacticaseibacillus paracasei ZY (Lcb. paracasei ZY) and Lacticaseibacillus rhamnosus SN12 (Lcb. rhamnosus SN12) presented higher GABA yields and adaptability to substrates. The optimized fermentation factors for GABA enhancement in orange juice were as follows: initial pH of 5.5, fermentation temperature of 37 °C, soluble solids content of 12.0 °Bx, inoculum ratio of Lcb. paracasei ZY to Lcb. rhamnosus SN12 as 1:1, inoculum size of 6 Log CFU/mL, and fermentation time of 96 h. Under these optimized conditions, the GABA content reached 0.89 g/L, representing a 39.06% increase compared to uninoculated orange juice. This indicates that RSM-based optimization is conducive to increasing GABA content in orange juice and provides a scientific basis for the development of GABA-enriched functional fermented juices. Full article

Roots infected by the forest pathogen Heterobasidion parviporum that remain in the soil after tree harvesting may serve as a source of inoculum for root infection of new generations of trees, thereby perpetuating outbreaks over time. As drained peat soils are evolutionary novel yet common habitat for commercial Picea abies stands in Northern Europe, the experiment was conducted to assess the mid-term viability of H. parviporum mycelium in root deadwood. Persistence of viable mycelia of H. parviporum in relation to root fragment volume and exposure period was assessed over the seven-year period. Additionally, the potential of transmission of the pathogen from root fragments to conifer seedlings was assessed. The likelihood of finding viable H. parviporum inoculum in Norway spruce root fragments depended on the size of fragments, indicating a higher likelihood in larger fragments, and on the time since burial, showing a substantial reduction in viable inoculum after seven years. We also documented the low infection rate from the root fragments to nearby Picea abies seedlings. The obtained results indicate the necessity for the removal of larger root fragments during soil preparation in commercial Norway spruce stands on drained peat soils to reduce infection potential. Full article

Monascus pigments (MPs) are valuable natural colorants, but their industrial production is often hampered by scarce high-yield strains and inefficient processes. In this study, a novel MPs-producing strain was isolated from red yeast rice and named as Monascus purpureus HC-5. This strain exhibited notable hydrolase activities, indicating a high efficiency in substrate utilization. In addition, using rice as the optimal substrate, the key parameters of solid-state fermentation were optimized. Response surface analysis revealed that soaking time and temperature were the most critical influencing factors. The optimal combination conditions were an inoculum size of 8.91%, a soaking time of 13.59 h, and a temperature of 32 °C. Under these optimized conditions, the MPs yield reached 2185 ± 255.7 U/g, which displayed an approximately four-fold increase compared to the initial unoptimized process. Briefly, this study identified a strain of Monascus purpureus and optimized its solid-state fermentation conditions, which significantly increased the yield of MPs. This provides an important theoretical basis and scientific evidence for the large-scale industrial production of MPs. Full article

Fermented tea beverage (FTB) has garnered significant attention owing to its unique combination of tea and wine flavors and its potential health benefits. This study investigates FTB co-fermented using different inoculum sizes of L. plantarum HYY-S10 and P. pastoris, evaluating physicochemical properties during the fermentation process. The final FTB products were comprehensively evaluated for their antioxidant activity, organic acid content, sensory characteristics, volatile flavor compounds, and microbial diversity. Compared with natural fermentation, the 1:1 mixed fermentation of these two microorganisms enhanced the antioxidant capacity and organic acid content of FTB. Furthermore, sensory evaluation revealed higher overall acceptability. Analysis of volatile compounds demonstrated an increase in the production of alcohols, esters, and ketones, leading to enhanced malty, fruity, and creamy aromas in FTB. Among these compounds, 3-methyl-1-butanol, phenylethyl alcohol, 1,2-propanediol, and 3-hydroxy-2-butanone play pivotal roles in shaping the flavor profile. High-throughput sequencing analysis identified Lactobacillus and Weizmannia as dominant bacteria, while Pichia or Issatchenkia was found to be dominant fungi. This study provides a theoretical foundation for the production of FTB through mixed fermentation with L. plantarum HYY-S10 and P. pastoris while contributing to the practical application of FTB production through mixed fermentation techniques. Collectively, our findings demonstrate that the 1:1 co-fermentation of L. plantarum HYY-S10 and P. pastoris is a promising strategy for developing novel fermented tea beverages with enhanced functional properties and complex, desirable flavors, offering valuable insights for the industrial production of specialty FTBs. 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

Grifola frondosa is a valuable medicinal and edible mushroom whose industrial cultivation and developmental mechanisms remain poorly understood. In this study, we systematically investigated the optimal cultivation parameters and molecular basis of fruiting body development using the white strain Gr0001+3 through integrated physiological and transcriptomic approaches. The results showed that the optimal liquid medium composition was glucose (28.5 g/L), yeast extract (11.5 g/L), and MgSO₄ (2 g/L), with a C/N ratio of 10:1. This composition achieved a mycelial biomass of 2.333 g/L via an orthogonal design. Ideal culture conditions were 100 mL/250 mL liquid volume, 10% inoculum size, and pH 4.0 in single-factor experiments. The fruiting body developmental transcriptomes were analyzed in four stages: early primordia (EP), middle primordia (MP), late primordia (LP), and mature fruiting body (FB). Principal component analysis revealed distinct transcriptional profiles, with greater similarities among later developmental stages. Differential gene expression peaked during the LP vs. FB transition. Functional enrichment (GO/KEGG) showed conserved biological processes in the MP-LP-FB transitions. Heat shock proteins (hsp_78/hsp_82) and the cAMP signaling pathway component (PKAC) were involved in fruiting body development, based on RT-qPCR. This work establishes practical cultivation parameters and offers fundamental insights into the molecular regulation of G. frondosa development, providing a comprehensive foundation for advancing the industrial production of this mushroom. Full article

Due to its high content of lignocellulose, cotton stalk is difficult to degrade naturally and utilize effectively, so it is often regarded as waste. In this study, the effects of Pleurotus ostreatus XH005, Lactiplantibacillus plantarum LP-2, and cellulase enzyme on the cotton stalk substrate under aerobic solid-state fermentation (SSF) conditions were investigated, and the metabolites were analyzed to identify potential functional compounds in the cotton-stalk-fermented feed. Preliminary optimization results obtained through single-factor experiments were as follows: fermentation time 14 days, XH005 inoculum size 8.00% (v/m), material-to-water ratio 1:0.50 (v/m), LP-2 inoculum size 2.00% (v/m), and cellulase addition 0.60% (m/m). Based on these single-factor experimental results, XH005 inoculum size, LP-2 inoculum size, material-to-water ratio, and cellulase addition were selected as independent variables. Through response surface methodology (RSM) optimization experiments, 29 experimental groups were designed. Subsequently, based on Box–Behnken analysis of variance (ANOVA) of lignin and cellulose content, along with contour and response surface plots, the optimal aerobic solid-state fermentation parameters were determined as follows: fermentation time 14 days, XH005 inoculum: 7.00% (v/m), material-to-water ratio: 1:0.55 (v/m), LP-2 inoculum: 2.00% (v/m), and cellulase enzyme addition: 0.65% (m/m). Results showed that compared with the control group (CK), the optimized group exhibited a 27.65% increase in lignin degradation rate and a 47.14% increase in cellulose degradation rate. Crude protein (CP) content increased significantly, while crude fiber (CF), detergent fiber and mycotoxin contents decreased significantly. Non-targeted metabolic analysis indicated that adding cellulase and inoculating Pleurotus ostreatus XH005 and Lactiplantibacillus plantarum LP-2 in aerobic SSF of cotton straw feed produced functionally active substances such as kaempferol (C343), carvone (C709) and trilobatin (C604). Therefore, this study demonstrates that microbial-enzyme co-action SSF significantly enhances the nutritional composition of cotton stalk hydrolysate. Furthermore, this hydrolysate is suitable for the production of functional compounds, endowing the fermented feed with health-promoting properties and enhancing the utilization of cotton processing byproducts in the feed industry. Full article

This study established a biological fermentation process using Saccharomyces cerevisiae and Lactobacillus plantarum to deodorize squid cartilage homogenate. The optimal fermentation conditions for S. cerevisiae were determined as follows: fermentation time 105 min, temperature 34 °C, and inoculum size 0.85%. For L. plantarum, the optimum conditions were 79 min, 34.5 °C, and 4.5% inoculum. Based on electronic nose and HS-SPME-GC-MS analyses, S. cerevisiae outperformed L. plantarum in eliminating key offensive odor compounds, especially sulfur-containing compounds and aldehydes, while promoting the formation of pleasant aroma compounds such as esters and ketones (e.g., carvone and δ-pentenol). Mechanistic insights suggest that the enhanced deodorization efficiency of S. cerevisiae may be attributed to its multi-pathway synergistic metabolism, involving enzymes like dioxygenases and sulfide oxidases that facilitate the conversion of malodorous substances into odorless or pleasantly aromatic compounds. These findings provide a valuable theoretical and practical foundation for the high-value utilization of squid processing by-products and propose a promising bio-deodorization strategy for aquatic products. Full article

Background: Mitis group non-pneumococcal streptococci (MGNPS), specifically Streptococcus mitis, Streptococcus infantis and Streptococcus oralis, have recently been shown to cause pneumonia and/or bacteremia. These organisms often have capsular (cps) operons resembling those in pneumococci, and some express cps-generated polysaccharides that antigenically cross-react with pneumococcal capsular serotypes. But, to date, a series of MGNPS isolates has not been studied by electron microscopy (EM) for the presence of a capsule. Methods: We studied 21 MGNPS; 11 were isolated from sputum and determined to have caused pneumonia, 3 were isolated from blood, and 7 were commensal isolates cultured from the oral cavity of healthy adults. Two reacted with a pneumococcal anticapsular antibody. Isolates were fixed with two different protocols and examined by transmission EM. Results: EM of MGNPS after standard fixation and staining with uranyl acetate did not show capsules. In contrast, the 21 MGNPS isolates that we studied after fixation with ruthenium red and lysine acetate were all shown to be encapsulated. The thickness and density of capsules was related to their species: Streptococcus pneumoniae had the most prominent encapsulation and Streptococcus oralis had the least. However, within a species, there was no apparent difference in capsules between disease-causing and colonizing strains. Conclusions: EM with ruthenium red staining demonstrated capsules on 21 MGNPS, but within a species, there was no apparent difference between disease-causing and commensal isolates. It seems reasonable to conclude that the capsule, together with inoculum size, host’s ability to clear aspirated organisms, and other as yet unidentified virulence factors, all contribute to the pathogenesis of MGNPS pneumonia. Full article

With the rise of environmental protection and health topics in recent years, microbial production of red pigments has gradually become a research hotspot. Red pigment possesses biological properties such as anticancer and antioxidant activities and has a wide range of potential applications in the fields of food and medicine. In this paper, a red pigment-producing strain was screened from rice soil to provide a reserve for obtaining natural and safe red pigments. Methods: The strain LSY1-2 was identified using morphological and 16S rDNA molecular biological identification. The fermentation conditions for red pigment production were optimised to improve pigment yield, and the best conditions were analysed using response surface methodology. Finally, the stabilisation conditions of red pigment were analysed to determine the difficulty of retention. Results: The molecular ecology was identified as the bacterium Arthrobacter sp. of the genus Arthrobacter. The optimal red pigment production medium for the strain was determined by a one-way test with the carbon source beef extract, the nitrogen source peptone, the inoculum size 2%, the temperature 27 °C, the pH value 7, and the rotational speed 160 rpm. Response surface optimisation determined the optimal red pigment production conditions as the incubation temperature of 26.43 °C, the pH value of 6.89, and the rotational speed of 162.77 rpm, which resulted in the yield of red pigment under these optimal conditions as 0.883 U/mL. The stability of red pigment was best under the condition without light, and poorer under conditions of above 50 °C, strong acid, strong alkali, and more than 3% oxidant, and Fe³⁺ had a greater effect on the stability. Conclusions: Strain LSY-1 can produce stable red pigment under the optimised red pigment-producing conditions, which provides a reference for the large-scale production of natural red pigment and subsequent related research. Full article

Kluyveromyces marxianus exhibits advantages such as strong thermotolerance, rapid growth rate, and high safety, making it an excellent host cell for the production of bio-based products. In this study, two exopolysaccharides, KE1 and KE2, were isolated from the fermentation broth of the strain K. marxianus KM-502, and their hydroxyl radical scavenging, DPPH scavenging, and Fe²⁺-reducing activities were evaluated. In vitro antioxidant assays demonstrated that exopolysaccharide KE2 exhibited superior antioxidant activity compared to KE1. The fermentation conditions were optimized using single-factor experiments followed by response surface methodology (RSM). The optimized fermentation process revealed that the most suitable fermentation medium consisted of 8% sucrose, 1.99% peptone, and 0.13% CaCl₂, while the optimal fermentation conditions were a medium volume of 74 mL in a 300 mL flask, pH 6.7, an inoculum size of 1.99%, a temperature of 30 °C, a shaking speed of 160 r/min, and a cultivation time of 96 h. After optimizing the fermentation conditions of K. marxianus KM-502, the exopolysaccharide (EPS) yield reached 5842.42 mg/L, representing a 22.77-fold increase compared to the yield before optimization. In summary, this study isolated exopolysaccharides KE1 and KE2 from K. marxianus KM-502. These exopolysaccharides demonstrated significant antioxidant activities, and the fermentation conditions for exopolysaccharide production were optimized. The findings of this study will facilitate the further development and utilization of exopolysaccharides from K. marxianus. Full article

Coffee cherry pulp (CCP), a coffee by-product rich in pectin and phenolic compounds, serves as a valuable substrate for microbial enzyme production, improving the nutritional and antioxidant properties of poultry feed. This study evaluated the potential of Kluyveromyces marxianus ST5 to produce pectin-degrading enzymes using CCP. Under unoptimized conditions, the pectin lyase (PL) and polygalacturonase (PG) activities were 3.29 ± 0.22 and 6.32 ± 0.13 U/mL, respectively. Optimization using a central composite design (CCD) identified optimal conditions at 16.81% (w/v) CCP, 5.87% (v/v) inoculum size, pH 5.24, and 30 °C for 48 h, resulting in PL and PG activities of 9.17 ± 0.20 and 15.78 ± 0.14 U/mL, representing increases of 178.7% and 149.7% over unoptimized conditions. Fermented CCP was further evaluated using an in vitro chicken gastrointestinal digestion model. Peptide release increased by 66.2% compared with unfermented CCP. Antioxidant capacity also improved, with significant increases observed in DPPH (32.4%), ABTS (45.0%), and FRAP (42.3%) assays, along with an 11.1% increase in total phenolic content. These results demonstrate that CCP bioconversion by K. marxianus ST5 enhances digestibility and antioxidant properties, supporting its potential as a sustainable poultry feed additive and contributing to the valorization of agro-industrial waste. Full article