Enzyme Activity Research Articles

Environmental concentrations of 6PPD and 6PPD-quinone induce hepatic lipid metabolism disorders in male black-spotted frogs

Aquatic environments are generally contaminated with N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and its oxidation product 6PPD-quinone (6PPD-Q). Recently, 6PPD-Q was found lethally toxic to some specific species, especially salmonid silverfish. This study investigated male black-spotted frogs (Pelophylax nigromaculatus) exposed to 6PPD and 6PPD-Q with different environmental concentrations (0, 1, and 10 μg/L) for 21 days, after which biochemical, metabolomic, gene expression analyses, and molecular docking were conducted. 6PPD and 6PPD-Q were both found to bioaccumulate in frogs’ livers in a dose-dependent manner and produce a significant reduction of the hepatosomatic index. Metabolomics data showed that 6PPD and 6PPD-Q induced distinct alterations in metabolite expression, predominantly within pathways associated with the biosynthesis of unsaturated fatty acids as well as the metabolism of arachidonic and linoleic acids. Exposure to 10 μg/L 6PPD and 6PPD-Q increased the cholesterol level by 2.22 and 4.35 folds, and the triglyceride level by 1.90 and 2.25 folds, respectively. 6PPD-Q inhibited the enzyme activity and gene expression involved in lipolysis, and promoted the lipid synthesis. Moreover, 6PPD and 6PPD-Q bound to peroxisome proliferators-activated receptors of α and γ. In conclusion, 6PPD and 6PPD-Q with environmental concentrations induced frogs’ lipid metabolism disorders. These findings contribute to our understanding of 6PPD and 6PPD-Q health risks in amphibians.

The effect of gelatinized brown rice extract on type 2 diabetes mellitus via inhibition of insulin resistance mediators in HepG2 cells

The purpose of this study evaluated effects of gelatinized brown rice extract (GBE) on type 2 diabetes mellitus by analyzing antioxidant activity, polysaccharide-degrading enzymes activity, and regulation of insulin secretion and glucose transport-related factors in human liver cells (HepG2). Quantified polyphenols and flavonoids in extract showed 6.7 mg gallic acid equivalent/g dry matter (DM) and 5.3 mg quercetin equivalent/g DM, respectively, with DPPH and ABTS radical scavenging activities confirmed to 67.1 ~ 77.7%. Additionally, extract inhibited alpha-glucosidase activity by 81.9%, thereby demonstrating potential for improving blood glucose regulation. To demonstrate alleviation of type 2 diabetes through mitigation of insulin resistance and promotion of glucose transport, expression of genes related to insulin receptor genes (Insulin Receptor Substrate-1, Protein Kinase B) increased by 18.5 ~ 28.3%, while expression of counterregulatory hormone genes (Insulin-like Growth Factor-1) decreased by 33.3%. Additionally, expression of glucose transporter proteins (Glucose Transporter Type-4, 2) increased by 30.9 ~ 42.0%, and expression of proteins that reduce insulin sensitivity (Insulin Receptor Substrate-2) decreased by 34.6%. These results indicated that insulin resistance in hepatocytes alleviated, and glucose transport promoted, leading to decreased blood glucose levels.

Antiviral Effects and Mechanisms of Active Ingredients in Tea

Viruses play a significant role in human health, as they can cause a wide range of diseases, from mild illnesses to severe and life-threatening conditions. Cellular and animal experiments have demonstrated that the functional components in tea, such as catechins, theaflavins, theanine, and caffeine, exhibit significant inhibitory effects on a diverse array of viruses, including influenza, rotavirus, hepatitis, HPV, and additional types. The inhibition mechanisms may involve blocking virus–host recognition, interfering with viral replication, enhancing host immune responses, and inhibiting viral enzyme activity. This article reviews the research progress on the antiviral effects of tea’s functional components and their related mechanisms, hoping to contribute to future studies in this field.

High Stability and Reusability of Papain Immobilized on the Non‐Toxic Magnetic Dialdehyde Starch Nanoparticles

AbstractPapain is widely used in food, drug, and bioactive peptide production and must be immobilized onto carriers with biocompatibility. Dialdehyde starch (DAS) can be a good biocompatible cross‐linker according to its active aldehyde groups. In the present study, the magnetic nanoparticles dialdehyde starch (MDASN), synthesized by DAS and Fe3O4 magnetic nanoparticles (Fe‐MNP), are successfully used to immobilize papain to improve the enzymic activity. The structure and morphology of DAS, MDASN, and immobilized papain onto magnetic dialdehyde starch nanoparticles (papain‐MDASN) are characterized detailly. The morphology of DAS is like a flat ball, and that of Fe‐MNP and papain‐MDASN are spherical and clumpy. The particle size of Fe‐MNP and papain‐MDASN are small, resulting in a large surface electrostatic effect and partial agglomeration. Enzymic activity studies of papain‐MDASN exhibit that the immobilized papain on MDASN represents better temperature resistance, alkaline resistance, thermal stability, and reusability, and its activity recovery is up to 68.21%. Papain onto magnetic dialdehyde starch nanoparticles (MDASN) may enhance its potential application in production processes.

Genome-wide associated study identifies FtPMEI13 gene conferring drought resistance in Tartary buckwheat.

Tartary buckwheat is known for its ability to adapt to intricate growth conditions and to possess robust stress-resistant properties. Nevertheless, it remains vulnerable to drought stress, which can lead to reduced crop yield. To identify potential genes involved in drought resistance, a genome-wide association study on drought tolerance in Tartary buckwheat germplasm was conducted. A gene encoding pectin methylesterase inhibitors protein (FtPMEI13) was identified, which is not only associated with drought tolerance but also showed induction during drought stress and abscisic acid (ABA) treatment. Further analysis revealed that overexpression of FtPMEI13 leads to improved drought tolerance by altering the activities of antioxidant enzymes and the levels of osmotically active metabolites. Additionally, FtPMEI13 interacts with pectin methylesterase (PME) and inhibits PME activity in response to drought stress. Our results suggest that FtPMEI13 may inhibit the activity of FtPME44/FtPME61, thereby affecting pectin methylesterification in the cell wall and modulating stomatal closure in response to drought stress. Yeast one-hybrid, dual-luciferase assays, and electrophoretic mobility shift assays demonstrated that an ABA-responsive transcription factor FtbZIP46, could bind to the FtPMEI13 promoter, enhancing FtPMEI13 expression. Further analysis indicated that Tartary buckwheat accessions with the genotype resulting in higher FtPMEI13 and FtbZIP46 expression exhibited higher drought tolerance compared to the others. This suggests that this genotype has potential for application in Tartary buckwheat breeding. Furthermore, the natural variation of FtPMEI13 was responsible for decreased drought tolerance during Tartary buckwheat domestication. Taken together, these results provide basic support for Tartary buckwheat breeding for drought tolerance.

Exploring antitumor activity of novel imidazo[2,1-b]thiazole and imidazo[1,2-a]pyridine derivatives on MDA-MB-231 cell line: Targeting VEGFR-2 enzyme with computational insight

Our study explored the anticancer potential of novel heterocyclic compounds, specifically 6a-d, 8a-d, 12a-d, and 13a-d, which are derived from imidazo[2,1-b]thiazole and imidazo[1,2-a]pyridine and linked through a hydrazide moiety. These compounds were assessed for their anticancer activity toward the MDA-MB-231 breast cancer cell line to evaluate their effectiveness in inhibiting cancer cell proliferation. Among the compounds tested, 13c and 13d emerged as the most active, with IC50 values of 4.40 ± 2.87 µM and 4.69 ± 2.55 µM, respectively. These two compounds were further investigated for their effects on VEGFR-2 enzymatic activity, cell cycle progression, and apoptosis, then 13c and 13d were further evaluated for their impact on DNA fragmentation using the comet assay. Both compounds demonstrated a significant increase in DNA fragmentation, with levels of damage being twice as high as those observed in the untreated control cells. Molecular docking studies through VEGFR-2 demonstrated that compounds 13c and 13d bind to VEGFR-2 in a manner comparable to the co-crystallized ligand sunitinib I. Further analysis using density functional theory highlighted their favorable physical properties. Additionally, computational evaluations of ADME and drug-likeness suggest that these derivatives hold promise and merit further investigation. The ultimate goal is to develop effective, safe, and orally bioavailable VEGFR-2 inhibitors for potential use in anticancer therapy.

Functional Evaluation of a Novel Homozygous ADCY3 Variant Causing Childhood Obesity

Adenylate cyclase 3 (ADCY3) is a transmembrane protein predominantly expressed in the primary cilia of neurons. It plays a vital role in converting ATP to cAMP, a secondary messenger that regulates various downstream signaling pathways such as carbohydrates and lipids metabolism. Homozygous loss-of-function variants in the ADCY3 gene lead to severe early-onset obesity and insulin resistance whereas gain-of-function variants protect against obesity. To describe a novel pathogenic ADCY3 variant implicated in early-onset obesity and functionally characterize this variant via in vitro and in silico validation, we identified a novel homozygous nonsense variant c.2520C>G, p.Thr840X in the ADCY3 gene using gene panel sequencing in a four-year-old girl. She was born to first-cousin consanguineous parents. The patient presented with severe obesity, and exhibited hepatomegaly and insulin resistance, with other biochemical and hormonal tests being normal. In vitro and in silico functional analyses showed downregulation and impaired activation of the ADCY3 protein. Our findings contribute to existing research that supports the role of ADCY3 in the genetic pathogenesis of early-onset obesity. In vitro and in silico functional characterization of the novel p.Thr840X variant showed impaired enzymatic activity leading to receptor loss of function, consistent with the patient’s phenotype. Genetic testing is essential in severe early-onset obesity and early diagnosis could benefit patients with personalized treatment strategies.

Oral N-acetylcysteine ameliorates liver fibrosis and enhances regenerative responses in Mdr2 knockout mice

Cholangiopathies are poorly understood disorders with no effective therapy. The extrahepatic biliary tree phenotype is less studied compared to the intrahepatic biliary injury in both human disease and Mdr2−/− mice, the established cholestatic mouse model. This study aimed to characterize the extra hepatic biliary tree of Mdr2−/− mice at various ages and to determine if injury can be repaired with the antioxidant and glutathione precursor N-acetyl-L-Cysteine treatment (NAC). We characterized extra hepatic bile ducts (EHBD)s at various ages from 2 to 40 weeks old FVB/N and Mdr2−/− mice. We examined the therapeutic potential of local NAC ex vivo using EHBD explants at early and late stages of injury; and systematic therapy by in vivo oral administration for 3 weeks. EHBD and liver sections were assessed by histology and immunofluorescent stains. Serum liver enzyme activities were analyzed, and liver spatial protein expression analysis was performed. Mdr2−/− mice developed progressive EHBD injury, similar to extrahepatic PSC. NAC treatment of ex vivo EHBD explants led to improved duct morphology. In vivo, oral administration of NAC improved liver fibrosis, and decreased liver enzyme activities. Spatial protein analysis revealed cell-type specific differential response to NAC, collectively indicating a transition from pro-apoptotic into proliferative state. NAC treatment should be further investigated as a potential therapeutic option for human cholangiopathies.

Effects of Cow-Dung Vermicomposting on Soil Carbon Mineralization and Temperature Sensitivity in Camellia oleifera Forest

Soil carbon mineralization plays an important role in the carbon cycle of terrestrial ecosystems. When it comes to the soil carbon cycle, however, research on how carbon mineralization characteristics of fertilized Camellia oleifera forest soil respond to temperature changes remains limited. This study used an indoor constant temperature incubation method to examine the effects of the vermicomposting of cow dung by applying it at three different quantities (A: 0.8 kg earthworm + 62.5 kg cow dung/Camellia oleifera; B: 1.6 kg earthworm + 125 kg cow dung/Camellia oleifera; C: 2.4 kg earthworm + 187.5 kg cow dung/Camellia oleifera) and set a control group with Camellia oleifera forest not being fertilized (CK). This research was conducted with incubators set at 5 °C, 15 °C, 25 °C, and 35 °C, and with continuous monitoring of soil carbon mineralization characteristics and temperature sensitivity of organic carbon mineralization. The results showed significant increases in soil MBC, MBN, DOC, DON, NO3−-N, and NH4+-N in groups with applications of cow-dung vermicomposting compared to CK. Except at 35 °C, soil respiration in the Camellia oleifera of Group A was consistently the strongest. The maximum soil carbon emission (C0) was determined through a simulation of potential carbon emissions, with all correlation coefficients exceeding 0.95. The contents of TC and TN were positively correlated with MBC and MBN (p <0.001), while the C: Nmicro was negatively correlated with TN, AN, MBN, and inorganic nitrogen. Based on temperature sensitivity (Q10), the influence of temperature on soil mineralization rate was observed. The vermicomposting of cow dung had a noticeable effect, as Group B showed significantly stronger enzyme activity compared to other groups. These results indicate that changes in MBC can impact the stability of soil carbon mineralization. The roles of soil moisture and microorganisms should be considered when predicting dynamic changes in the soil carbon pool of Camellia oleifera when applying fertilizers and improving its soil carbon sequestration capacity.

Chemoenzymatic Cyclization by Vanadium Chloroperoxidase for Synthesis of 4-Hydroxyisochroman-1-ones.

4-Hydroxyisochroman-1-ones belong to the class of the secondary metabolite 3,4-dihydroisocoumarins. They exhibit a wide range of biological activities. These compounds can be synthesized through halocyclization using hypervalent iodine species or N-bromosuccinimide, followed by hydrolysis. Nonetheless, the reactions required specific conditions and generated toxic byproducts. In this study, Curvularia inaequalis vanadium chloroperoxidase (CiVCPO) catalyzed the chemoenzymatic cyclization of 2-vinylbenzoic acids with different electron-donating groups (1a-1e) to produce good yields of 4-hydroxyisochroman-1-ones (3a-3e) by adding KBr and H2O2 in citrate buffer (pH 5). The reaction mixture contained 30% DMSO to improve substrate solubility without enzyme activity loss. The condition is more environmentally friendly than chemical methods. Therefore, it offers an alternative approach for synthesizing 4-hydroxyisochroman-1-ones.

DAAO Mutant Sites among Different Mice Strains and Their Effects on Enzyme Activity.

Previous studies reported that D-amino acid oxidase (DAAO) activity was closely associated with neuropathic pain, cognitive characteristics of schizophrenia and so on. To determine DAAO mutant sites in different strains of mice and their effects on enzyme activity, we successfully constructed a prokaryotic expression system for heterologous expression of DAAO in vitro. There were total five nucleotide mutations distributed in exons 2, 8, 9, 10 of C57 mice. Three mutations located on exons 8 and 9 were synonymous mutations and had no variation on the encoded amino acid. The remaining two mutations in exons 2 (V64A) and 10 (R295H) were non-synonymous mutations, which might affect enzymatic activity and protein structure of mDAAO. Based on the determination of the kinetic constants and IC50 of mDAAO mutants in vitro, the differences in amino acid levels at these two sites (V64A, R295H) increased the affinity of C57 DAAO with substrate and enhanced its catalytic efficiency. Besides, the IC50 value of C57 DAAO was less than that of Balb/c and other DAAO mutants (SUN: reducted by about 11.9%; CBIO: reducted by about 26.5%), which meant that the affinity of C57 DAAO with CBIO was higher.

Transcriptome Profiling of Two Camellia japonica Cultivars with Different Heat Tolerance Reveals Heat Stress Response Mechanisms

Camellia (Camellia japonica) is a semi-shaded plant that is highly vulnerable to heat stress. To investigate the mechanisms underlying heat stress in C. japonica, two C. japonica cultivars, “Xiaotaohong” and “Zhuapolian”, which exhibit significant differences in heat tolerance, were selected from four common cultivars. The selection methods included phenotypic observations and physiological index detection, including relative electric conductivity (REC), malondialdehyde (MDA) content, superoxide dismutase (SOD) enzyme activity, relative water content (RWC), and chlorophyll content. RNA-seq analysis yielded 980 million reads and identified 68,455 differentially expressed genes (DEGs) in the two C. japonica cultivars during heat stress compared to the control samples. Totals of 12,565 and 16,046 DEGs were differentially expressed at 16 h and 32 h, respectively, in “Xiaotaohong” during heat stress. In “Zhuapolian”, 40,280 and 37,539 DEGs were found at 16 h and 32 h, respectively. KEGG enrichment analysis revealed that both cultivars were enriched in the “plant hormone signal transduction” and “circadian rhythm” pathways at two stages, indicating the critical role these pathways play in the heat stress response. The differences in the tolerance between the two cultivars are likely linked to pathways such as “plant hormone signal transduction”, “photosynthesis”, and “circadian rhythm”. Some members of heat shock proteins (HSPs) are associated with the heat stress response. It is speculated that transcription factor families contributing to the tolerance differences include AP2/ERF, C3H, bHLH, bZIP, and MYB-related with a small number of heat shock factors (HSFs) also induced by the stress. In conclusion, these results reveal the changes in the physiological indices and molecular networks of two C. japonica cultivars under heat stress. This study lays the foundation for the breeding of superior heat-resistant C. japonica cultivars and for further molecular research.

Effects of Replacing Fish Meal with Rubber Seed Cake on Growth, Digestive, Antioxidant and Protein Metabolism of Juvenile Asian Red-Tailed Catfish (Hemibagrus wyckioides)

An 8-week feeding trial was conducted to assess the impact of replacing fish meal (FM) with rubber seed cake (RSC) on growth performance, digestive enzyme activity of the gut, antioxidant capacity and protein metabolism-related parameters of plasma and liver in juvenile Asian red-tailed catfish (Hemibagrus wyckioides) with an average body weight of 3.21 g. Four isonitrogenous (41.08 ± 0.17) and isolipidic (10.07 ± 0.11) diets were formulated, incorporating RSC at a level of 0%, 15%, 30%, and 45% (w/w) to progressively replace FM. Dietary inclusion of 15–30% RSC did not significantly affect growth performance (p > 0.05). However, the replacement of FM with RSC resulted in linear reductions in intestinal trypsin and amylase activities, with a significant reduction in intestinal amylase activity observed at the 45% RSC inclusion level. Dietary inclusion of 30–45% RSC decreased plasma glutamate dehydrogenase and aspartate aminotransferase activities, but increased plasma adenosine monophosphate deaminase and hepatic γ-glutamyltransferase activities. This may indicate that the high substitution of FM by RSC may affect the homeostasis of amino acid metabolism. Dietary inclusion of 15% RSC did not affect serum and hepatic antioxidant enzyme activities; however, dietary inclusion of 45% RSC significantly increased plasma malondialdehyde level, but decreased catalase activity. Furthermore, dietary inclusion of 30–45% RSC significantly increased hepatic lactate dehydrogenase activity. These results demonstrated that replacing a portion of FM with RSC is feasible, and dietary inclusion of 15% RSC did not have significant adverse effects on growth performance, digestive function and antioxidant capacity of H. wyckioides.

Optimizing Fermentation Strategies for Enhanced Tryptophan Production in Escherichia coli: Integrating Genetic and Environmental Controls for Industrial Applications

Tryptophan is an essential aromatic amino acid widely used in the pharmaceutical, agricultural, and feed industries. Microbial fermentation, mainly using Escherichia coli, has become the preferred method for its production due to sustainability and lower costs. Optimizing tryptophan production requires careful control of various fermentation parameters, including nutrients, pH, temperature, and dissolved oxygen (DO) levels. Glucose, as the primary carbon source, must be fed at controlled rates to avoid metabolic overflow, which leads to by-product accumulation and reduced production efficiency. Nitrogen sources, both organic (such as yeast extract) and inorganic (like ammonium), influence biomass growth and tryptophan yield, with ammonium levels requiring careful regulation to avoid toxic accumulation. Phosphate enhances growth but can lead to by-product formation if used excessively. pH is another critical factor, with an optimal range between 6.5 and 7.2, where enzyme activity is maximized. Temperature control promotes growth and production, particularly between 30 °C and 37 °C. High DO levels increase tryptophan titers by boosting the pentose phosphate pathway and reducing by-products like acetate. Furthermore, surfactants and supplements such as betaine monohydrate and citrate help alleviate osmotic stress and enhance precursor availability, improving production efficiency. Careful manipulation of these parameters allows for high-density cell cultures and significant tryptophan accumulation, making microbial fermentation competitive for large-scale production.

Host dependent specialized metabolism of nitrogen export in actinorhizal nodules induced by Frankia cluster-2.

Frankia cluster-2 strains are diazotrophs that engage in root nodule symbiosis with actinorhizal plants of the Cucurbitales and the Rosales. Previous studies have shown that an assimilated nitrogen source, presumably arginine, is exported to the host in nodules of Datisca glomerata (Cucurbitales), while a different metabolite is exported in the nodules of Ceanothus thyrsiflorus (Rosales). To investigate if an assimilated nitrogen form is commonly exported to the host by cluster-2 strains, and which metabolite would be exported in Ceanothus, we analysed gene expression levels, metabolite profiles, and enzyme activities in nodules. We conclude that the export of assimilated nitrogen in symbiosis seems to be a common feature for Frankia cluster-2 strains, but which source is host-dependent. The export of assimilated ammonium to the host suggests that 2-oxoglutarate is drawn from the TCA cycle at a high rate. This specialised metabolism obviates the need for the reductive branch of the TCA cycle. We found several genes encoding enzymes of the central carbon and nitrogen metabolism were lacking in Frankia cluster-2 genomes: the glyoxylate shunt and succinate semialdehyde dehydrogenase. This led to a linearization of the TCA cycle, and we hypothesize this could explain the low saprotrophic potential of Frankia cluster-2.

Resveratrol Inhibits Nucleosome Binding and Catalytic Activity of PARP1

The natural polyphenol resveratrol is a biologically active compound that interacts with DNA and affects the activity of some nuclear enzymes. Its effect on the interaction between nucleosomes and poly(ADP-ribose) polymerase-1 (PARP1) and on the catalytic activity of PARP1 was studied using Western blotting, spectrophotometry, electrophoretic mobility shift assay, and single particle Förster resonance energy transfer microscopy. Resveratrol inhibited PARP1 activity at micro- and sub-micromolar concentrations, but the inhibitory effect decreased at higher concentrations due to the aggregation of the polyphenol. The inhibition of PARP1 by resveratrol was accompanied by its binding to the enzyme catalytic center and a subsequent decrease in PARP1 affinity to nucleosomal DNA. Concurrent binding of talazoparib to the substrate binding pocket of PARP1, which occurs in the presence of resveratrol, restores the interaction of PARP1 with nucleosomes, suggesting that the binding sites of resveratrol and talazoparib overlap. The data suggest that resveratrol can be classified as a natural inhibitor of PARP1.

Deciphering nitrogen dynamics in aeroponics: physio-biochemical and enzymatic responses influencing nitrogen use efficiency in contrasting potato genotypes

Excessive use of nitrogen (N) in crops, such as potatoes, can lead to economic and environmental repercussions. We hypothesized that potato genotypes with resilient root systems and high genetic capabilities for nitrogen-use efficiency (NUE) could effectively mitigate these challenges. Consequently, we investigated intraspecific variations and characteristics within six distinct potato genotypes exhibiting diverse NUEs in response to varying nitrogen levels in an aeroponic system. The morpho-physiological and biochemical properties showed significant genotypic variations, especially related to the N-assimilating enzyme levels and root characteristics. Notably, the root systems of all genotypes demonstrated greater responsiveness to low nitrogen levels, with genotype C17 showcasing the most substantial root system irrespective of nitrogen concentration. Root morphological traits displayed robust positive correlations with NUtE, primarily influenced by genotype rather than nitrogen concentration. Conversely, nitrogen levels, displaying positive correlations with NUpE, influenced growth and activities of N-assimilating enzymes. Based on their distinct root systems, metabolic activities, and NUE profiles, genotypes C17 and C11 were determined to be N-efficient and N-inefficient, respectively. This study provides novel insights into the physiological and biochemical mechanisms underlying nitrogen use efficiency in potato genotypes under aeroponic conditions, offering potential targets for breeding programs, optimizing fertilizer management and cultivation strategies to improve crop performance under nitrogen-deficient conditions. Future investigations, employing multi-omics approaches, will elucidate key genes and pathways in nitrogen metabolism, potentially offering avenues to enhance root architecture and improve NUE.

Defense Mechanisms of Xylopia aromatica (Lam.) Mart. in the Dry Season in the Brazilian Savanna

Water availability and light during the dry and rainy seasons in the Cerrado may influence plants’ stomatal movement and the entry of CO2 for organic synthesis, which is the main electron drain. A lower stomatal conductance may contribute to the energy accumulated in the chloroplasts being directed towards the synthesis of compounds, which contributes to the activity of antioxidant enzymes to neutralize reactive oxygen species. Xylopia aromatica is a characteristic Cerrado species, and it is often recommended for recovering degraded areas. This study aimed to investigate the influence of the dry and rainy seasons on the metabolic adjustments of Xylopia aromatica in a portion of the Brazilian savanna in the state of São Paulo. In the rainy season, better photosynthetic performance led to greater investment in essential oil production. In the dry season, the plants may direct part of their reducing sugars to the syntheses of carotenoids and anthocyanins, which may help the antioxidant enzymes to neutralize reactive oxygen species. Carotenoids assist in the dissipation of photosystem energy, which has the potential to cause oxidative stress. During this season, lower stomatal conductance prevented excessive water loss. These results suggest the acclimatization of this species to the conditions of the Brazilian savanna.

Simultaneous saccharification and fermentation for d-lactic acid production using a metabolically engineered Escherichia coli adapted to high temperature

BackgroundEscherichia coli JU15 is a metabolically engineered strain capable to metabolize C5 and C6 sugars with a high yield of d-lactic acid production at its optimal growth temperature (37 °C). The simultaneous saccharification and fermentation process allow to use lignocellulosic biomass as a cost-effective and high-yield strategy. However, this process requires microorganisms capable of growth at a temperature close to 50 °C, at which the activity of cellulolytic enzymes works efficiently.ResultsThe thermotolerant strain GT48 was generated by adaptive laboratory evolution in batch and chemostat cultures under temperature increments until 48 °C. The strain GT48 was able to grow and ferment glucose to d-lactate at 47 °C. It was found that a pH of 6.3 conciliated with GT48 growth and cellulase activity of a commercial cocktail. Hence, this pH was used for the SSF of a diluted acid-pretreated corn stover (DAPCS) at a solid load of 15% (w/w), 15 FPU/g-DAPCS, and 47 °C. Under such conditions, the strain GT48 exhibited remarkable performance, producing d-lactate at a level of 1.41, 1.42, and 1.48-fold higher in titer, productivity, and yield, respectively, compared to parental strain at 45 °C.ConclusionsIn general, our results show for the first time that a thermal-adapted strain of E. coli is capable of being used in the simultaneous saccharification and fermentation process without pre-saccharification stage at high temperatures.

Advances in the biosynthesis of D-allulose.

D-allulose is a rare monosaccharide and a C-3 epimer of D-fructose. It has physiological functions, such as antihyperglycemic, obesity-preventing, neuroprotective, and reactive oxygen species (ROS) scavenging effects, making it an ideal sugar substitute. The synthesis methods for D-allulose include chemical synthesis and biosynthesis. Chemical synthesis requires strict reaction conditions and tends to produce byproducts. Biosynthesis is mainly an enzymatic process. Enzymatic catalysis for the conversion of starch or glycerol to D-allulose is performed mainly by enzymes such as isoamylase (IA), glucose isomerase (GI), D-allulose 3-epimerase (DPE), D-allulose-6-phosphate 3-epimerase (A6PE), D-allulose 6-phosphate phosphatase (A6PP), ribitol 2-dehydrogenase (RDH), glycerophosphate kinase (GK), glycerophosphate oxidase (GPO), and dihydroxyacetone phosphate (DHAP)-dependent aldolase. Biosynthesis is a more energy-efficient process, producing fewer harmful by-products and pollutants, and significantly reducing negative environmental impacts. Furthermore, the specific catalytic activity of enzymes facilitates the production of compounds of higher purity, thereby facilitating the isolation and purification of the products. It has thus become the main method for producing D-allulose. This article reviews the progress in research on the biosynthetic production of D-allulose, focusing on the enzymes involved and their enzymatic properties, and discusses the production prospects for D-allulose.