Increased Enzyme Activity Research Articles

Efficient D-allulose synthesis under acidic conditions by auto-inducing expression of the tandem D-allulose 3-epimerase genes in Bacillus subtilis

BackgroundD-allulose, a hexulose monosaccharide with low calorie content and high sweetness, is commonly used as a functional sugar in food and nutrition. However, enzyme preparation of D-allulose from D-frutose was severely hindered by the non-enzymatic browning under alkaline and high-temperature, and the unnecessary by-products further increased the difficulties in separation and extraction for industrial applications. Here, to address the above issue during the production process, a tandem D-allulose 3-epimerase (DPEases) isomerase synergistic expression strategy and an auto-inducible promoter engineering were levered in Bacillus subtilis 168 (Bs168) for efficient synthesis of D-allulose under the acidic conditions without browning.ResultsFirst, based on the dicistron expression system, two DPEases with complementary functional characteristics from Dorea sp. CAG:317 (DSdpe) and Clostridium cellulolyticum H10 (RCdpe) were expressed in tandem under the promoter HpaII in one cell. A better potential strain Bs168/pMA5-DSdpe-RCdpe increases enzyme activity to 18.9 U/mL at acidic conditions (pH 6.5), much higher than 17.2 and 16.7 U/mL of Bs168/pMA5-DSdpe and Bs168/pMA5-RCdpe, respectively. Subsequently, six recombinant strains based on four constitutive promoters were constructed in variable expression cassettes for improving the expression level of protein. Among those engineered strains, Bs168/pMA5-PspoVG-DSdpe-PsrfA-RCdpe exhibited the highest enzyme activity with 480.1 U/mL on fed-batch fermentation process in a 5 L fermenter at pH 6.5, about 2.1-times higher than the 228.5 U/mL of flask fermentation. Finally, the maximum yield of D-allulose reached as high as 163.5 g/L at the fructose concentration (50% w/v) by whole-cell biocatalyst.ConclusionIn this work, the engineered recombinant strain Bs168/pMA5-PspoVG-DSdpe-PsrfA-RCdpe was demonstrated as an effective microbial cell factory for the high-efficient synthesis of D-allulose without browning under acidic conditions. Based on the perspectives from this research, this strategy presented here also made it possible to meet the requirements of the industrial hyper-production of other rare sugars under more acidic conditions in theory.

Exploring strategies for the use of mixed microalgae in cellulase production and its application for bioethanol production

AbstractImproving the enzymatic hydrolysis processes of cellulosic materials can be considered a key aim for bioethanol production. Cellulase production using mixed microalgae by mono and co‐cultivation of Trichoderma reesei and Aspergillus niger has not yet been reported. In this study, the effect of different concentration ratios of cellulose and microalgae on the production of cellulases was investigated. Media containing equal mass percentages of microalgae and cellulose showed the highest cellulase activity (3.3 U mL−1) among other tested ratios using co‐cultivation of fungi. The optimal percentage of microalgae (50%) increased enzyme activity by about 20% compared with pure cellulose due to necessary and rare elements in the microalgae. Subsequently, fermentation of this sample to bioethanol using Saccharomyces cerevisiae demonstrated a yield of 0.46 g ethanol/g glucose (92% of the theoretical value). The microalgae ratio is therefore an important factor and can be optimized to gain the highest enzyme activity and improve the cost‐effectiveness of bioethanol production from microalgae. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd

Influence of Dinitrosyl Iron Complexes on the Activity of Enzymes, Indicators of Cardiovascular Diseases

Increased enzyme activities of matrix metalloproteinase, myeloperoxidase, renin, histone deacetylase, and poly (ADP-ribose) polymerase are indicators of the development of cardiovascular diseases. Therefore, the search for new inhibitors of these enzymes is relevant. The effect of iron dinitrosyl complexes and nitric oxide donors on these enzymes' activity was studied. It has been shown by fluorescence spectroscopy that DNICs (at concentration 2x10-4M) inhibit the activity of these enzymes. The constants of half-maximal inhibition of enzymes under the action of DNICs were determined (10-4-10-5M). The results showed that DNICs are effective inhibitors of matrix metalloproteinase, myeloperoxidase, renin, and polyadenine-ribose polymerase but do not affect histone deacetylase activity. These DNICs have been shown to have therapeutic potential for treating cardiovascular diseases.

Microbial growth rates, carbon use efficiency and enzyme activities during post-agricultural soil restoration

Microorganisms are critical for litter decomposition, organic carbon (C) and nutrient transformations in soil, corresponding to the vegetation succession. The dynamics of microbial activities and ecological functions during the soil recovery after agricultural land use (post-agricultural restoration) remains unclear. We investigated the effects of vegetation and soil restoration duration on active microbial biomass, microbial growth rates, C use efficiency (CUE, analyzed by 14C glucose utilization), and enzyme activities in three soil types of Russia: Haplic Luvisol in a deciduous forest (chronosequence from 0 to 37 years), Luvic Phaeozem in forest steppe (0–66 years), and Haplic Phaeozem in forest steppe (0–42 years). The microbial CUE (0.66–0.82) decreased during restoration and was highly dependent on soil type: the lowest in Luvisol and the highest in Haplic Phaeozem. The activities of β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase, leucine aminopeptidase, and acid phosphatase increased during post-agricultural restoration. Microbial growth rates and the proportion of active microorganisms increased with restoration, reflecting a shift of microbial community to fast-growing decomposers (mainly r strategists) caused by large litterfall from recovered natural vegetation. The increase of the portion of active microorganisms and microbial growth rates was correlated with activities of enzymes responsible for C, N and P cycling. In conclusion, the post-agricultural restoration activates microorganisms, raises microbial growth, increases enzyme activities and accelerates microbially-mediated C and nutrient turnover.

Foliar application of salicylic acid and calcium chloride delays the loss of chlorophyll and preserves the quality of broccoli during storage.

Consumer awareness of broccoli's unusual color, rich flavor, and concentration of desired phytochemicals has led to a steady increase in consumption in recent years. However, its short shelf-life, which is linked with quick discoloration and degeneration after harvest, limits industrial production and marketing. The effect of pre-harvest salicylic acid (SA) and calcium chloride (Ca) and their combination on the post-harvest quality of broccoli during storage (5± 1°C) was explored in this study. The foliar spray treatments reduced weight loss of broccoli head during storage. At the end of storage, Ca (2%) alone and in combination with SA (0.01%) significantly maintained the chlorophyll concentration rather than control. The total phenols, flavonoid, and antioxidant capacity of the Ca (2%) + SA (0.01%) treated samples was significantly greater than the control. SA (0.01%) alone or in conjunction with Ca (2%), showed higher catalase (CAT) activity; however, Ca (1%), alone or in combination with SA (0.01%), showed higher peroxidase (POD) activity. Generally, the marketability of the treated broccoli was significantly greater than the control at the end of storage. Based on these findings, we believe Ca (2%) + SA (0.01%) improves the antioxidant system, delays chlorophyll degradation, and extends the shelf life of broccoli heads stored at 5± 1°C. It is proposed that the green color, marketability, and nutrient content of broccoli during postharvest handling and storage can be retained longer by foliar application of this treatment. PRACTICAL APPLICATIONS: Broccoli (Brassica oleracea L. Italaia) is a widely-consumed floral green vegetable due to its high content of nutrients and bioactive compounds. However, after harvest, florets rapidly senesce and suffer from yellowing which affects the quality of broccoli. The senescence of post-harvest broccoli is characterized by fresh weight loss, chlorophyll degradation, and a significant reduction in nutritional content. Therefore, preventing the decline in the quality of harvested broccoli is essential to maintain its economic and nutritional value. The results of this study showed that pre-harvest foliar application of Ca (2%) + SA (0.01%) with delayed weight loss, chlorophyll degradation, preservation of antioxidant compounds, and increased enzyme activity has a positive effect in maintaining broccoli heads quality during cold storage.

Post-harvest Application of Methyl Jasmonate or Prohydrojasmon Affects Color Development and Anthocyanins Biosynthesis in Peach by Regulation of Sucrose Metabolism.

The roles of methyl jasmonate (MeJA) and prohydrojasmon (PDJ) in postharvest color development and anthocyanins biosynthesis in the skin of peach fruit remain unclear. In this study, peach fruit were infiltrated with MeJA (200 μM) or PDJ (40 μM) and stored at 22°C for 7 days. The results showed that treatment with MeJA or PDJ had a positive effect on red color formation in peach fruits due to anthocyanins accumulation (∼120% increase). This was attributed to increased enzyme activities, and enhanced transcript abundance of the genes associated with anthocyanins biosynthesis, induced by MeJA or PDJ. Both MeJA and PDJ promoted sucrose biosynthesis, and the subsequently elevated levels of the sucrose during storage were positively correlated with anthocyanins accumulation (0.49) and the activities of key biosynthesis enzymes (0.42–0.79). Based on these findings, we proposed that MeJA or PDJ treatments promote anthocyanins biosynthesis by regulating sucrose metabolism during the postharvest storage of peach fruit.

Bactericidal process and practicability for environmental water sterilization by solar-light-driven Bi2WO6-based photocatalyst

Pathogenic microorganism has always been a major threat to human health, which results in infectious diseases and even massive death. In the present study, the solar-light-driven photocatalyst Ag/Ag2O/BiPO4/Bi2WO6 was firstly used for water disinfection. The results showed the Ag/Ag2O/BiPO4/Bi2WO6 composite completely inactivated 7.40 log10 cfu/mL Escherichia coli within only 20 min under light irradiation. The inactivation mechanism was systematically investigated from the antioxidant enzymes, cell membrane, intracellular components and active species involved in the disinfection process. At the early stage of disinfection, the antioxidant system was initiated and increased enzyme activities to fight oxidative attack. Unfortunately, with accumulation of oxidative damage, the activities of antioxidant enzymes were suppressed, leading to deterioration of defense system. After destruction of defense system, cell membrane was destroyed gradually, monitored by K+ leakage and microscopic images. Furthermore, severe destruction of cell membrane led to leakage of nucleic acid and proteins, suggesting the irreversible death of bacteria. The photogenerated active species including superoxide radicals and holes played major roles in bactericidal process. In addition, the composite exhibited high adaptability for water disinfection at a wide range of environmental factors including light intensity, temperature, pH and humic acid. The slight release of Ag+ (<0.1 mg/L) and high stability of photocatalysts during successive disinfection experiments further implied its great potential for application. This work introduced an efficient solar-light-driven photocatalyst Ag/Ag2O/BiPO4/Bi2WO6, which exhibited a promising prospect for practical application, in hope of providing more useful information for water disinfection.

Effect of various factors on ejaculate fertility in vitro

Introduction. Current demographic situation in Russia is characterized by decreasing birth rate. According to the World Health Organization, percentage of child-free marriages in various countries is 10–15 %. In Russia, the National Medical Research Center for Obstetrics, Gynecology, and Perinatology named after Academician V.I. Kulakov states that this number is 17 %. More than 4 million men suffer from infertility of various types. In recent years, pathologies of male reproductive function have achieved medical and social significance due to progressively decreasing sperm fertility. Fertility disorders are considered multi-factor conditions caused by internal and external factors and leading to pathological changes in sex organs. Correction of pathologies of male fertility does not always lead to positive results. Therefore, it is important to develop and study effective pharmaceuticals affecting the main fertility parameters.The study objective is to investigate the effect of various biological pharmaceuticals, physical and chemical factors on parameters of ejaculate fertility in vitro.Materials and methods. Experiments with a protein-peptide complex (PPC), methylene blue, and hydrogen peroxide were performed on human semen. After semen dilution, the sample was studied under the microscope and sperm motility and other ejaculate parameters were evaluated per the 5th edition WHO standard. Experiments were performed at 20–22 ºС. Statistical data analysis was performed using the Student’s t-test. Differences were considered statistically significant at р &lt;0.05.Results. The results show increased motility in the fraction of active motile sperm in first 30 minutes after incubation with methylene blue. In case of initial asthenospermia, active motility increased by 72 %, in case of normospermia by 89 %. After 2 hours, all motility fractions were at the baseline level.The experiments also showed significant changes in sperm motility in the presence of PPC preparation in the ejaculate: increase in sperm motility was observed beginning at 30-minute mark and this level persisted through 3 hours of observation. A more pronounced change, by 60 %, was observed in the active motile sperm; total motility increased by up to 30 %. After 24 hours, sperm motility remained close to the baseline level, the number of normal sperm forms and live cells did not change. Dependence of the motility change on the preparation concentration should be noted: the highest increase was observed at PPC concentration with total protein level of 10–12 mg/mL. Higher concentrations did not have a positive effect on sperm motility. In experiments with low hydrogen peroxide concentration, a positive effect on sperm motility was observed.Conclusions. Sperm motility is supported by glycolysis energy, and one of the glycolysis enzymes glyceraldehyde 3-phosphate dehydrogenase is tightly bound to the fibrous layer of the flagellum, activation of metabolic pathways leading to increased enzyme activity, increased sperm motility. The mechanism of the observed effect is not entirely clear, however, the obtained data demonstrate potential benefits of further studies on use of pharmaceuticals in andrological and reproductive practice, assisted reproductive technologies, as well as for stimulation of sperm motility in further experimental studies.

Geographic Origin and Host Dependent Metabolic Responses Affect Spodoptera frugiperda Susceptibility to Insecticides

Spodoptera frugiperda is one of the most harmful pest threatening crops in tropical regions. It is particularly difficult to control due to its high polyphagia, mobility and the evolution of resistance. One of the main strategies enabling this insect to extend its geographic range, is the expression of a wide repertoire of detoxification enzymes, that neutralizes diverse environmental xenobiotics as well as insecticides. Hence adaptation to particular ecological niches can lead to different enzyme expression which consequently may affect its control. Even though the molecular basis of adaption is well known, there is not much applied studies regarding the effect of the geographic region in S. frugiperda physiology and management. Thus, the objective of this work was to determine the activity of detoxification enzymes, as well as the susceptibility to insecticides of S. frugiperda from distinct geographic origins in local hosts plants. Larvae from Pelotas, a region characterized by crop succession with oats and maize and larvae from Cascavel, which is characterized by highly intensive maize systems thought the year were used in the experiments. Our study showed that only larvae from Pelotas had increased enzyme activity after feeding on oat plants. In most insecticide treatments, mortality increased on population Cascavel after feeding on oats, the same was not observed on larvae from Pelotas. Our results are in accordance with previous studies that pointed distinct geographic conditions could lead to genetic variability and different responses to control. Information on S. frugiperda dynamics is essential to develop local management programs as well to better understand the complex nature of plant-insect interactions.

Soil enzymes in response to climate warming: Mechanisms and feedbacks

Abstract Soil enzymes are central to ecosystem processes because they mediate numerous reactions that are essential in biogeochemical cycles. However, how soil enzyme activities will respond to global warming is uncertain. We reviewed the literature on mechanisms linking temperature effects on soil enzymes and microbial communities, and outlined a conceptual overview on how these changes may influence soil carbon fluxes in terrestrial ecosystems. At the enzyme scale, although temperature can have a positive effect on enzymatic catalytic power in the short term (i.e. via the instantaneous response of activity), this effect can be countered over time by enzyme inactivation and reduced substrate affinity. At the microbial scale, short‐term warming can increase enzymatic catalytic power via accelerated synthesis and microbial turnover, but shifts in microbial community composition and growth efficiency may mediate the effect of warming in the long term. Although increasing enzyme activities may accelerate labile carbon decomposition over months to years, our literature review highlights that this initial stage can be followed by the following phases: (a) a reduction in soil carbon loss, due to changing carbon use efficiency among communities or substrate depletion, which together can decrease microbial biomass and enzyme activity and (b) an acceleration of soil carbon loss, due to shifts in microbial community structure and greater allocation to oxidative enzymes for recalcitrant carbon degradation. Studies that bridge scales in time and space are required to assess whether there will be an attenuation or acceleration of soil carbon loss through changes in enzyme activities in the very long term. We conclude that soil enzymes determine the sensitivity of soil carbon to warming, but that the microbial community and enzymatic traits that mediate this effect change over time. Improving representation of enzymes in soil carbon models requires long‐term studies that characterize the response of wide‐ranging hydrolytic and oxidative enzymatic traits—catalytic power, kinetics, inactivation—and the microbial community responses that govern enzyme synthesis. Read the free Plain Language Summary for this article on the Journal blog.

Effects of Nitrogen and Phosphorus Addition on Soil Extracellular Enzyme Activity and Stoichiometry in Chinese Fir (Cunninghamia lanceolata) Forests.

Soil extracellular enzymes play an important role in microbial functions and soil nutrient cycling in the context of increasing N deposition globally. This is particularly important for Chinese fir (Cunninghamia lanceolata) forests because of the decline in soil fertility induced by successive rotation. In this study, we aimed to determine the effects of simulated N deposition (N30: 30 kg ha−2 year−1; N60: 60 kg ha−2 year−1) and phosphorus addition (P20: 20 mg kg−1; P40: 40 mg kg−1) on the activity and stoichiometry of soil extracellular enzymes related to soil C, N, and P cycling in Chinese fir. The results showed that N addition alone increased the activity of soil β-1,4 glucosidase (BG) but decreased the activity of N-acetyl-β-d-glucosidase (NAG) and leucine aminopeptidase (LAP). N addition increased the ratios of soil enzymes, C:N and C:P, alleviated microbial N-limitation, and aggravated microbial C-limitation. P addition alone increased enzyme activity, and P40 addition increased the ratio of BG to soil microbial biomass carbon (MBC), and (NAG + LAP):MBC activity ratio, thereby aggravating C restriction. N and P co-addition significantly affected soil extracellular enzyme activity and stoichiometry. For instance, BG activity and BG:MBC activity ratio increased significantly under the N30 + P40 treatment, which intensified C-limitation. Soil pH was the main factor influencing enzyme activity, and these variables were positively correlated. The stoichiometric relationships of enzyme reactions were coupled with soil pH, total nitrogen (TN), and available phosphorus (AP). Our results indicate that changes in soil characteristics induced by N and P inputs influence the activities of soil microorganisms and result in changes in microbial resource acquisition strategies. This study provides useful insights into the development of management strategies to improve the productivity of Chinese fir forests under scenarios of increasing N deposition.

The role of divalent iron cations in the growth, adhesive properties and extracellular adaptation mechanisms of Propionibacterium sp

The present study aims to examine PAB culture, synthesizing a significant number of iron-containing enzymes and capable of adhesion. Results show that increased iron concentration increased enzymes activity in all strains studied. An increase of iron ions level increasing up to 0.50–0.60 mg/ml leads to a 1.3-fold and 2-dold increase of catalase and SOD activity respectively, peroxidase activity was virtually unchanged. Optimal iron ions Fe2+ doses to ensure active PAB growth were determined. Of all the cultures studied P. fredenreichii subsp. shermanii AC-2503 has high adhesion: AAI = 5.1; MAI = 5.60; erythrocyte involvement rate = 87%. It was shown that certain iron ion concentrations increased the specific growth rate of PAB (P. freudenrichii subsp. freudenrichii AC-2500 (0.3 mg/ml) and other strains (0.4 mg/ml). A further increase in the iron ions concentration slows bacterial growth, while excessive content inhibits metabolism, including defense mechanisms that offset the negative effects of the metal. Our subsequent studies will focus on the effect of other metal ions on the metabolism of bacteria, mainly lactic acid bacteria, which are important biotechnological objects of the industry similar to propionic acid bacteria.

Erythroid spectrin binding modulates peroxidase and catalase activity of heme proteins.

Hemoglobin oxidation due to oxidative stress and disease conditions leads to the generation of ROS (reactive oxygen species) and membrane attachment of hemoglobin in-vivo, where its redox activity leads to peroxidative damage of membrane lipids and proteins. Spectrin, the major component of the red blood cell (RBC) membrane skeleton, is known to interact with hemoglobin and, here this interaction is shown to increase hemoglobin peroxidase activity in the presence of reducing substrate ABTS (2', 2'-Azino-Bis-3-Ethylbenzothiazoline-6-Sulfonic Acid). It is also shown that in the absence of reducing substrate, spectrin forms covalently cross-linked aggregates with hemoglobin which display no peroxidase activity. This may have implications in the clearance of ROS and limiting peroxidative damage. Spectrin is found to modulate the peroxidase activity of different hemoglobin variants like A, E, and S, and of isolated globin chains from each of these variants. This may be of importance in disease states like sickle cell disease and HbE-β-thalassemia, where increased oxidative damage and free globin subunits are present due to the defects inherent in the hemoglobin variants associated with these diseases. This hypothesis is corroborated by lipid peroxidation experiments. The modulatory role of spectrin is shown to extend to other heme proteins, namely catalase and cytochrome-c. Experiments with free heme and Raman spectroscopy of heme proteins in the presence of spectrin show that structural alterations occur in the heme moiety of the heme proteins on spectrin binding, which may be the structural basis of increased enzyme activity.

Characterization of a Recombinant Laccase B from Trametes hirsuta MX2 and Its Application for Decolorization of Dyes.

Trametes hirsuta is able to secrete laccase isoenzymes including constitutive and inducible forms, and has potential application for bioremediation of environmental pollutants. Here, an inducible group B laccase from T. hirsuta MX2 was heterologously expressed in Pichia pastoris, and its yield reached 2.59 U/mL after 5 days of methanol inducing culture. The optimal pH and temperature of recombinant laccase (rLac1) to 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were 2.5 and 60 °C, respectively. Metal ions showed different effect on rLac1 which Mg2+, Cu2+, and K+ increased enzyme activity as their concentration increased, whereas Zn2+, Na+, and Fe2+ inhibited enzyme activity as their concentration increased. rLac1 showed good tolerance to organic solvents, and more than 42% of its initial activity remained in 10% organic solvents. Additionally, rLac1 exhibited a more efficient decolorization ability for remazol brilliant blue R (RBBR) than for acid red 1 (AR1), crystal violet (CV), and neutral red (NR). Molecular docking results showed RBBR has a stronger binding affinity with laccase than other dyes by interacting with substrate binding cavity of enzyme. The results indicated rLac1 may be a potential candidate for dye removal from textile wastewater.

Heavy metal-induced oxidative stress and alteration in secretory proteins in yeast isolates.

In the recent years, yeasts have evolved as potent bioremediative candidates for the detoxification of xenobiotic compounds found in the natural environment. Candida sp. are well-studied apart from Saccharomyces sp. in heavy metal detoxification mechanisms. In the current study, Candida parapsilosis strain ODBG2, Candida sp. strain BANG3, and Candida viswanathii strain ODBG4 were isolated from industrial effluents and contaminated ground water, and were studied for their metal tolerance. Among these three isolates, the metal tolerance was found to be more towards Lead (Pb 2mM), followed by Cadmium (Cd 1.5mM) and Chromium [Cr(VI), 1mM]. On further exploring the involvement of primary defensive enzymes in these isolates towards metal tolerance, the anti-oxidative enzyme superoxide dismutase was found to be prominently high (25% with respect to the control) during first 24h of metal-isolate interaction. The Catalase enzyme assay was observed to have increased enzyme activity at 48h. It also triggered the activity of peroxidases, which lead to the increase in reduced glutathione in the organism by 0.87-1.9-fold as a metal chelator and also as a second-line defensive molecule. The exoproteome profile showed the early involvement (exponential growth phase) of secreted proteins (low-molecular-weight) of about ~ 40-45kDa under Cd and Pb stress (0.5mM). The exoproteome profiling under heavy metal stress in Candida parapsilosis strain ODBG2 and Candida viswanathii strain ODBG4 is the first report.

Facile Cellulase Immobilisation on Bioinspired Silica.

Cellulases are enzymes with great potential for converting biomass to biofuels for sustainable energy. However, their commercial use is limited by their costs and low reusability. Therefore, the scientific and industrial sectors are focusing on finding better strategies to reuse enzymes and improve their performance. In this work, cellulase from Aspergillus niger was immobilised through in situ entrapment and adsorption on bio-inspired silica (BIS) supports. To the best of our knowledge, this green effect strategy has never been applied for cellulase into BIS. In situ entrapment was performed during support synthesis, applying a one-pot approach at mild conditions (room temperature, pH 7, and water solvent), while adsorption was performed after support formation. The loading efficiency was investigated on different immobilisation systems by Bradford assay and FTIR. Bovine serum albumin (BSA) was chosen as a control to optimize cellulase loading. The residual activity of cellulase was analysed by the dinitro salicylic acid (DNS) method. Activity of 90% was observed for the entrapped enzyme, while activity of ~55% was observed for the adsorbed enzyme. Moreover, the supported enzyme systems were recycled five times to evaluate their reuse potential. The thermal and pH stability tests suggested that both entrapment and adsorption strategies can increase enzyme activity. The results highlight that the entrapment in BIS is a potentially useful strategy to easily immobilise enzymes, while preserving their stability and recycle potential.

Effects of Dietary Sodium Acetate on Growth Performance, Fillet Quality, Plasma Biochemistry, and Immune Function of Juvenile Golden Pompano (Trachinotus ovatus)

Six isonitrongenous and isolipidic diets were formulated to feed 360 fish (mean initial body weight: 6.06 ± 0.02 g) with graded levels of sodium acetate (SA1 (0), SA2 (250 mg/kg), SA3 (500 mg/kg), SA4 (1000 mg/kg), SA5 (2000 mg/kg), and SA6 (4000 mg/kg)) for 8 weeks. The results revealed that weight gain rate, specific growth rate, and feed intake of golden pompano were significantly increased in SA3 and SA4 treatments ( p &lt; 0.05 ). Dietary SA level significantly improved lipid contents and gumminess of muscle ( p &lt; 0.05 ). Supplement levels of dietary SA significantly influenced plasma biochemical parameters containing triglyceride, glucose, high-density lipoprotein cholesterol, complements, and immunoglobulin M ( p &lt; 0.05 ). Appropriate supplement levels of dietary SA significantly increased enzyme activities of hepatic superoxide dismutase and total antioxidant capacity and decreased malondialdehyde contents ( p &lt; 0.05 ). Furthermore, appropriate SA levels downregulated the expression levels of Keap1, IL-8, TNF-α, and NF-κB genes and upregulated the expression levels of Nrf2 and TGF-β genes of the spleen ( p &lt; 0.05 ). Excess SA caused negative effects for Trachinotus ovatus. The optimum supplement level of SA for juvenile golden pompano was evaluated to be 1423.67 mg/kg based on WGR.

Effects of different particle size of zero-valent iron (ZVI) during anaerobic digestion: Performance and mechanism from genetic level

Although zero valent iron (ZVI) has been widely studied as an additive in anaerobic digestion, the effect of ZVI particle size on anaerobic methane production and the mechanism by which this occurs have not been reported. This study investigated the effects of ZVI particles with different diameters (0.1 μm to 250 μm) on the glucose-substrate anaerobic digestion process. It was found that different particle sizes of ZVI had different optimal dosages, as 2 g/L of 48 μm ZVI increased methane production by 84.12% when compared with the blank group, whereas ZVI of 0.1 μm reached its optimal dosage at 0.5 g/L, increasing methane production by only 37.32%. Further study of the mechanism showed that 4 μm ZVI could increase the abundance of bacteria Bacteroidota and Proteobacteria (from 1.46% and 0.07% to 15.56% and 2.27%, respectively) and Archaea Methanosaeta (from 3.59% to 51.64%). Gene’s prediction showed that ZVI particles with a size range of 4–48 μm could facilitate cell replication and increase enzyme activity involved in methane production. Additionally, it could mediate direct interspecies electron transfer between fermentative bacteria and methanogens while avoiding cell lysis caused by the nano effect.

Improvement of the activity and thermostability of the L-glutamateoxidase by directed evolution and structure analysis

Glutamate oxidase (LGOX) is a kind of flavin proteases that can specifically catalyze the deamination of L-glutamate to α-ketoglutarate. It can be widely used in factory production, biosensors, clinical biochemical testing, etc. Therefore the directed evolution technology was used to construct a mutation library through error-prone PCR, and four mutants with increased enzyme activity were obtained through high-throughput screening: F94L, S280T, I282M, H533R. The S280TH533L mutant with the highest enzyme activity was obtained, and its enzyme activity increased by 90.7% compared with the wild type.

A novel simultaneous coupling of memory photocatalysts and microbial communities for alternate removal of dimethyl phthalate and nitrate in water under light/dark cycles

Efficient and sustainable removal of both organic and inorganic pollutants from contaminated water is an important but difficult task. Here, a novel chemical-biological coupling concept, namely simultaneous coupling of memory photocatalysts and microbial communities (SCMPMC), is proposed for the first time that alternates the removal of organic and inorganic pollutants under successive light/dark cycles. We established this novel coupling system with WO3/g-C3N4 memory photocatalysts and river sediment microbial communities, and applied it to alternately remove dimethyl phthalate (DMP) and nitrate under light/dark cycles. The performance of SCMPMC under the light/dark cycles (12/12 h) showed that ~84.90% of the DMP was removed mainly via robust photocatalytic oxidation during the light phase, and ~86.80% of the nitrate was removed via microbial reduction enhanced by photogenerated electrons stored in the WO3/g-C3N4 memory photocatalysts during the dark phase within one cycle. The microbial communities were positively affected by adding WO3/g-C3N4, as evidenced by increased enzyme activities, cellular antigen metabolism, and relative abundance of typical denitrifiers, including Proteobacteria and Bacteroidetes. These results will contribute to the development of promising decontamination methods and mechanisms to control water pollution driven by the natural day/night cycle.