Biosynthetic Profile in the Co-culture of Aspergillus sydowii and Bacillus subtilis to Produce Novel Benzoic Derivatives.

Microbial co-culture simulates the natural ecosystem through the combination of artificial microbes. This approach has been widely applied in the study of activating silent genes to reveal novel secondary metabolites. However, there are still challenges in determining the biosynthetic pathways. In this study, the effects of microbial co-culture on the morphology of the microbes were verified by the morphological observation. Subsequently, through the strategy combining substrate feeding, stable isotope labeling, and gene expression analysis, the biosynthetic pathways of five benzoic acid derivatives N1-N4 and N7 were demonstrated: the secondary metabolite 10-deoxygerfelin of A. sydowii acted as an inducer to induce B. subtilis to produce benzoic acid, which was further converted into 3-OH-benzoic acid by A. sydowii. Subsequently, A. sydowii used 3-OH-benzoic acid as the substrate to synthesize the new compound N2, and then N1, N3, N4, and N7 were biosynthesized upon the upregulation of hydrolase, hydroxylase, and acyltransferase during co-culture. The plate zone analysis suggested that the biosynthesis of the newly induced compounds N1-N4 was mainly attributed to A. sydowii, and both A. sydowii and B. subtilis were indispensable for the biosynthesis of N7. This study provides an important basis for a better understanding of the interactions among microorganisms, providing new ideas for studying the biosynthetic pathways of the newly induced secondary metabolites in co-culture.

Two-Step Enzymolysis of Antarctic Krill for Simultaneous Preparation of Value-Added Oil and Enzymolysate.

Antarctic krill is a crucial marine resource containing plenty of high-valued nutrients. However, krill oil as a single product has been developed by the current solvent extraction with high cost. From the perspective of comprehensive utilization of Antarctic krill, this study proposed a novel two-step enzymolysis-assisted extraction in attempt to produce value-added oil and enzymolysate simultaneously. After two-step chitinase/protease hydrolysis, the lipid yield increased from 2.09% to 4.18%, reaching 112% of Soxhlet extraction. The method greatly improved the yields of main components while reducing the impurity content without further refining. After optimization, the oil contained 246.05 mg/g of phospholipid, 80.96 mg/g of free eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and 0.82 mg/g of astaxanthin. The by-product enzymolysate was abundant in water-soluble proteins (34.35 mg/g), oligopeptides (13.92 mg/g), amino acids (34.24 mg/g), and carbohydrates (5.79 mg/g), which was a good source of functional nutrients. In addition, both oil and enzymolysate showed high antioxidant capacity. This novel method could simultaneously provide oil and enzymolysate amounting for 58.61% of dried krill.

Inducing secondary metabolite production of Aspergillus sydowii through microbial co-culture with Bacillus subtilis.

BACKGROUND: The co-culture strategy which mimics natural ecology by constructing an artificial microbial community is a useful tool to activate the biosynthetic gene clusters to generate new metabolites. However, the conventional method to study the co-culture is to isolate and purify compounds separated by HPLC, which is inefficient and time-consuming. Furthermore, the overall changes in the metabolite profile cannot be well characterized. RESULTS: A new approach which integrates computational programs, MS-DIAL, MS-FINDER and web-based tools including GNPS and MetaboAnalyst, was developed to analyze and identify the metabolites of the co-culture of Aspergillus sydowii and Bacillus subtilis. A total of 25 newly biosynthesized metabolites were detected only in co-culture. The structures of the newly synthesized metabolites were elucidated, four of which were identified as novel compounds by the new approach. The accuracy of the new approach was confirmed by purification and NMR data analysis of 7 newly biosynthesized metabolites. The bioassay of newly synthesized metabolites showed that four of the compounds exhibited different degrees of PTP1b inhibitory activity, and compound N2 had the strongest inhibition activity with an IC50 value of 7.967 µM. CONCLUSIONS: Co-culture led to global changes of the metabolite profile and is an effective way to induce the biosynthesis of novel natural products. The new approach in this study is one of the effective and relatively accurate methods to characterize the changes of metabolite profiles and to identify novel compounds in co-culture systems.

Pentacyclic triterpenes as α-glucosidase and α-amylase inhibitors: Structure-activity relationships and the synergism with acarbose.

In this paper, the inhibition of α-amylase and α-glucosidase by nine pentacyclic triterpenes was determined. For α-amylase inhibitory activity, the IC50 values of ursolic acid, corosolic acid, and oleanolic acid were 22.6±2.4µM, 31.2±3.4µM, and 94.1±6.7µM, respectively. For α-glucosidase inhibition, the IC50 values of ursolic acid, corosolic acid, betulinic acid, and oleanolic acid were 12.1±1.0µM, 17.2±0.9µM, 14.9±1.9µM, and 35.6±2.6µM, respectively. The combination of corosolic acid and oleanolic acid with acarbose showed synergistic inhibition against α-amylase. The combination of the tested triterpenes with acarbose mainly exhibited additive inhibition against α-glucosidase. Kinetic studies revealed that corosolic acid and oleanolic acid showed non-competitive inhibition and acarbose showed mixed-type inhibition against α-amylase. The results provide valuable implications for the triterpenes (ursolic acid, corosolic acid, and oleanolic acid) alone or in combination with acarbose as a therapeutic agent for the treatment of diabetes mellitus.

Wortmannilactones I-L, new NADH-fumarate reductase inhibitors, induced by adding suberoylanilide hydroxamic acid to the culture medium of Talaromyces wortmannii.

With the aim of finding more potential inhibitors against NADH-fumarate reductase (specific target for treating helminthiasis and cancer) from natural resources, Talaromyces wortmannii was treated with the epigenome regulatory agent suberoylanilide hydroxamic acid, which resulted in the isolation of four new wortmannilactones derivatives (wortmannilactones I-L, 1-4). The structures of these new compounds were elucidated based on IR, HRESIMS and NMR spectroscopic data analyses. These four new compounds showed potent inhibitory activity against NADH-fumarate reductase with the IC50 values ranging from 0.84 to 1.35µM.

Dynamic immobilization of bacterial cells on biofilm in a polyester nonwoven chemostat.

Cell immobilization plays an important role in biocatalysis for high-value products. It is necessary to maintain the viability of immobilized cells for bioconversion using viable cells as biocatalysts. In this study, a novel polyester nonwoven chemostat was designed for cell immobilization to investigate biofilm formation and the dynamic balance between adsorption and desorption of cells on polyester nonwoven. The polyester nonwoven was suitable for cell immobilization, and the cell numbers on the polyester nonwoven can reach 6.5 ± 0.38 log CFU/mL. After adding the polyester nonwoven to the chemostat, the fluctuation phenomenon of free bacterial cells occurred. The reason for this phenomenon was the balance between adsorption and desorption of bacterial cells on the polyester nonwoven. Bacterial cells could adhere to the surface of polyester nonwoven via secreting extracellular polymeric substances (EPS) to form biofilms. As the maturation of biofilms, some dead cells inside the biofilms can cause the detachment of biofilms. This process of continuous adsorption and desorption of cells can ensure that the polyester nonwoven chemostat has lasting biological activity.

Salting-out extraction of recombinant κ-carrageenase and phage T7 released from Escherichia coli cells.

Traditional technology of cell disruption has become one of the bottlenecks restricting the industrialization of genetic engineering products due to its high cost and low efficiency. In this study, a novel bioprocess of phage lysis coupled with salting-out extraction (SOE) was evaluated. The lysis effect of T7 phage on genetically engineered Escherichia coli expressing κ-carrageenase was investigated at different multiplicity of infection (MOI), meanwhile the phage and enzyme released into the lysate were separated by SOE. It was found that T7 phage could lyse 99.9% of host cells at MOI = 1 and release more than 90.0% of enzyme within 90 min. After phage lysis, 87.1% of T7 phage and 71.2% of κ-carrageenase could be distributed at the middle phase and the bottom phase, respectively, in the SOE system composed of 16% ammonium sulfate and 20% ethyl acetate (w/w). Furthermore, κ-carrageenase in the bottom phase could be salted out by ammonium sulfate with a yield of 40.1%. Phage lysis exhibits some advantages, such as mild operation conditions and low cost. While SOE can efficiently separate phage and intracellular products. Therefore, phage lysis coupled with SOE is expected to become a viable alternative to the classical cell disruption and intracellular product recovery.

Recycling reaction and separation for FACylation of loxenatide by trade-off between miscibility and immiscibility of reactants and product in methanol solution.

The growing demand and scale of production for fatty acid chain modified (FACylated) polypeptide has sparked the interest in novel production technologies. In this study, a recycling reaction and separation process was proposed and applied to the fatty acid chain modification (FACylation) of loxenatide (LOX), which was based on the difference in solubility between reactants and FACylated product. Especially, the mixed PBS-Methanol (MeOH) solution was designed to meet the demands for FACylation of LOX as well as separation of FACylated LOX and residual modifier. In order to ensure the efficient FACylation, a mixed 10% PBS-90% MeOH (v/v) solution was chosen to provide a good miscibility for two reactants, LOX and N-tetradecylmaleimide (C14-MAL). On the other hand, the immiscibility between reactant (C14-MAL) and FACylated product (N-tetradecyl-Loxenatide (C14-LOX)) could realize the separation of C14-LOX when the MeOH concentration was less than 30% (v/v). Based on this strategy, the recycling reaction and separation process for FACylation of LOX was established by adjusting the MeOH concentration in the mixed solution. The reaction yield and recovery of C14-LOX exceeded 97% and 94%, and the excess reactant C14-MAL could be recycled with a recovery of more than 80%. Furthermore, after purification by reversed-phase chromatography, C14-LOX showed good pharmacokinetic and pharmacodynamic properties in vivo. This study will have great application prospects in industrial production of C14-LOX.

Co-culture of Aspergillus sydowii and Bacillus subtilis induces the production of antibacterial metabolites.

The co-culture strategy, which mimics natural ecology by constructing an artificial microbial community, is a useful tool to activate the biosynthetic gene clusters to generate new compounds. However, without optimization of fermentation conditions, the antagonism between the microbes often interferes with the production of secondary metabolites. In this study, the fermentation conditions of co-culture of Aspergillus sydowii and Bacillus subtilis were optimized by response surface methodology to increase the production of active metabolites against Staphylococcus aureus. After optimization, the inhibitory rate of the co-culture extract was 74.62%, which was 29.20% higher than that of the initial conditions. Meanwhile, a total of 15 newly biosynthesized metabolites were detected only in optimized co-culture, occupying 13.2% of all detected metabolites. The structures of the 12 metabolites with high variable importance in projection score were elucidated by the established LC-MS/MS approach integrated with various metabonomic tools. Among them, 7 metabolites were newly induced and the content of other 5 metabolites increased by 1.1-2.4 folds in optimized co-culture. The bioassay of metabolites in co-culture against S. aureus indicated that compounds (-)- (7S)- 10-hydroxysydonic acid, serine sydonate and macrolactin U' contributed much to the increment of antibacterial activity. This study demonstrated that optimizing the fermentation conditions of co-culture was beneficial to changing the metabolite profile and effective to induce the biosynthesis of active metabolites.

Simultaneous solid-liquid separation and primary purification of clavulanic acid from fermentation broth of Streptomyces clavuligerus using salting-out extraction system.

Clavulanic acid (CA) is usually used together with other ß-lactam antibiotics as combination drugs to inhibit bacterial ß-lactamases, which is mainly produced from the fermentation of microorganism such as Streptomyces clavuligerus. Recently, it is still a challenge for downstream processing of low concentration and unstable CA from fermentation broth with high solid content, high viscosity, and small cell size. In this study, an integrated process was developed for simultaneous solid-liquid separation and primary purification of CA from real fermentation broth of S. clavuligerus using salting-out extraction system (SOES). First, different SOESs were investigated, and a suitable SOES composed of ethanol/phosphate was chosen and further optimized using the pretreated fermentation broth. Then, the optimal system composed of 20% ethanol/15% K2HPO4 and 10% KH2PO4 w/w was used to direct separation of CA from untreated fermentation broth. The result showed that the partition coefficient (K) and recovery yield (Y) of CA from untreated fermentation broth were 29.13 and 96.8%, respectively. Simultaneously, the removal rates of the cells and proteins were 99.8% and 63.3%, respectively. Compared with the traditional method of membrane filtration or liquid-liquid extraction system, this developed SOES showed the advantages of simple operation, shorter operation time, lower process cost and higher recovery yield of CA. These results demonstrated that the developed SOES could be used as an attractive alternative for the downstream processing of CA from real fermentation broth.

Biotransformation of steriodal saponins in Dioscorea zingiberensis C. H. Wright to diosgenin by Trichoderma harzianum.

Diosgenin is an important starting material in the steroidal hormone industry. Traditionally, diosgenin is mainly produced by acid hydrolysis of Dioscorea zingiberensis C. H. Wright (DZW) tubers. This method yields numerous byproducts that can cause serious pollution. In this study, diosgenin was obtained by biotransformation of steroidal saponins in DZW afforded by Trichoderma harzianum CGMCC 2979. The medium was optimized for maximum diosgenin production. The addition of phosphate buffer, surfactant Tween-85, and Fe(2+) increased the yield of diosgenin by 50.28%, 33.35%, and 22.07%, respectively. The optimum medium obtained by response surface methodology was composed of 60 mmol l(-1) phosphate buffer, 0.07% (w/v) Tween-85, and 0.93 mmol l(-1) Fe(2+). Under these conditions, a maximum diosgenin yield of 30.05 +/- 0.59 mg g(-1) was achieved, which was slightly higher than that obtained from traditional acid hydrolysis. By hydrolyzing the un-transformed steroidal saponins after biotransformation, the total diosgenin yield increased by 35% compared to traditional method. Moreover, chemical oxygen demand and residual reduced sugar in the wastewater produced by this integrated process were only 3.72% and 0.3%, respectively, that of the traditional acid hydrolysis method.

Solid-state Co-cultivation of Bacillus subtilis, Bacillus mucilaginosus, and Paecilomyces lilacinus Using Tobacco Waste Residue.

Agro-industrial wastes are excellent sources for solid-state culture to produce spores of microorganisms, whereas microbial co-cultivation is not fully exploited in solid-state culture. In this work, the co-cultivation of different strains of Bacillus subtilis, and three microbes of B. subtilis, Bacillus mucilaginosus, and Paecilomyces lilacinus was studied using a solid medium only composed of water and tobacco waste residue after extraction of nicotine and solanesol. The influences of matrix thickness, moister, temperature, and ratio of three microbes in seed on the cell growth and spore formation were studied. The maximum viable cells and spores of each microbe reached 1013 cfu/g when cultured alone at 30 °C in a medium containing 58.3% moisture. Co-cultivation of microbes stimulated cell growth and maximum viable cells of each microbe reached 1014 cfu/g, while spore production was inhibited and decreased to 1011 cfu/g. With decreasing amount of P. lilacinus in seed, total amount of spores was increased. When the seed with a ratio of 6:3:1 for B. mucilaginosus, B. subtilis, and P. lilacinus was inoculated, the total amount of spores reached 4.14 × 1012 cfu/g and the ratio was 1.7:0.7:1. These results indicate the potential of solid-state cultivation in the high production of spores from tobacco waste residue at low cost.

Dietary 5,6,7-Trihydroxy-flavonoid Aglycones and 1-Deoxynojirimycin Synergistically Inhibit the Recombinant Maltase-Glucoamylase Subunit of α-Glucosidase and Lower Postprandial Blood Glucose.

1-Deoxynojirimycin (1-DNJ) is the major effective component of mulberry leaves, exhibiting inhibitory activity against α-glucosidase. However, due to the low content of 1-DNJ in mulberry products, its level cannot meet the lowest dose to exhibit its activity. In this study, a combination of dietary 5,6,7-trihydroxy-flavonoid aglycones with 1-DNJ showed synergistic inhibitory activity against maltase of mice α-glucosidase and recombinant C- and N-termini of maltase-glucoamylase (MGAM) and baicalein with 1-DNJ exhibited the strongest synergistic effect. The synergistic effect of the combination was also confirmed by the maltose tolerance test in vivo. Enzyme kinetics, molecular docking, fluorescence spectrum, and circular dichroism spectrometry studies indicated that the major mechanism of the synergism is that baicalein was a positive allosteric inhibitor and bound to the noncompetitive site of MGAM, causing an increase of the binding affinity of 1-DNJ to MGAM. Our results might provide a theoretical basis for the design of dietary supplements containing mulberry products.

The activities of wortmannilactones against helminth electron transport chain enzymes, structure-activity relationships, and the effect on Trichinella spiralis infected mice.

Biotransformation of wortmannilactone F (3) using the marine-derived fungus DL1103 generated wortmannilactone M (1), a novel analog of wortmannilactone, which was a reduction product of 3 at the C-3 carbonyl group. The in vitro inhibitory activities of 10 wortmannilactones, including 1, against electron transport enzymes indicated that all the wortmannilactones were selective inhibitors of NADH-fumarate reductase and NADH-rhodoquinone reductase. The structure-activity relationship analysis showed that the relative configuration of C1" and C5", the positions of double bonds, the oxygen atoms in the dihydropyran moiety, and the keto-carbonyl group in the oxabicyclo-[2.2.1]-heptane moiety were important to the inhibitory activity of wortmannilactones. In vivo studies indicated that 3 significantly decreased the number and size of adult worms in Trichinella spiralis-infected mice in a dose-dependent manner. Notable changes in the cuticle and microvilli of T. spiralis were also observed. Our data provided useful information in the research and development of polyketides with dihydropyran and oxabicyclo [2.2.1] heptane moieties as antihelminthics.

A cell-based high-throughput screening assay for Farnesoid X receptor agonists.

OBJECTIVE: To develop a high-throughput screening assay for Farnesoid X receptor (FXR) agonists based on mammalian one-hybrid system (a chimera receptor gene system) for the purpose of identifying new lead compounds for dyslipidaemia drug from the chemical library. METHODS: cDNA encoding the human FXR ligand binding domain (LBD) was amplified by RT-PCR from a human liver total mRNA and fused to the DNA binding domain (DBD) of yeast GAL4 of pBIND to construct a GAL4-FXR (LBD) chimera expression plasmid. Five copies of the GAL4 DNA binding site were synthesized and inserted into upstream of the SV40 promoter of pGL3-promoter vector to construct a reporter plasmid pG5-SV40 Luc. The assay was developed by transient co-transfection with pG5-SV40 Luc reporter plasmid and pBIND-FXR-LBD (189-472) chimera expression plasmid. RESULTS: After optimization, CDCA, a FXR natural agonist, could induce expression of the luciferase gene in a dose-dependent manner, and had a signal/noise ratio of 10 and Z' factor value of 0.65. CONCLUSION: A stable and sensitive cell-based high-throughput screening model can be used in high-throughput screening for FXR agonists from the synthetic and natural compound library.

Dietary Flavonoids and Acarbose Synergistically Inhibit α-Glucosidase and Lower Postprandial Blood Glucose.

The inhibition of porcine pancreatic α-amylase and mammalian α-glucosidase by 16 individual flavonoids was determined. The IC50 values for baicalein, (+)-catechin, quercetin, and luteolin were 74.1 ± 5.6, 175.1 ± 9.1, 281.2 ± 19.2, and 339.4 ± 16.3 µM, respectively, against α-glucosidase. The IC50 values for apigenin and baicalein were 146.8 ± 7.1 and 446.4 ± 23.9 µM, respectively, against α-amylase. The combination of baicalein, quercetin, or luteolin with acarbose showed synergistic inhibition, and the combination of (+)-catechin with acarbose showed antagonistic inhibition of α-glucosidase. The combination of baicalein or apigenin with acarbose showed additive inhibition of α-amylase at lower concentrations and antagonistic inhibition at a higher concentration. Kinetic studies of α-glucosidase activity revealed that baicalein alone, acarbose alone, and the combination showed noncompetitive, competitive, and mixed-type inhibition, respectively. Molecular modeling revealed that baicalein had higher affinity to the noncompetitive binding site of maltase, glucoamylase, and isomaltase subunits of α-glucosidase, with glide scores of -7.64, -6.98, and -6.88, respectively. (+)-Catechin had higher affinity to the active sites of maltase and glucoamylase and to the noncompetitive site of isomaltase. After sucrose loading, baicalein dose-dependently reduced the postprandial blood glucose (PBG) level in mice. The combination of 80 mg/kg baicalein and 1 mg/kg acarbose synergistically lowered the level of PBG, and the hypoglycemic effect was comparable to 8 mg/kg acarbose. The results indicated that baicalein could be used as a supplemental drug or dietary supplement in dietary therapy for diabetes mellitus.

Combination of flavonoids from Oroxylum indicum seed extracts and acarbose improves the inhibition of postprandial blood glucose: In vivo and in vitro study.

The combined effect of Oroxylum indicum seed extracts (OISE) or major flavonoids from OISE and acarbose on reducing postprandial blood glucose (PBG) levels was investigated in vitro and in vivo. In vitro, the IC50 values of OISE and baicalein against α-glucosidase were 43.4±0.731µgmL-1 and 25.9±0.412µgmL-1 respectively. A combination of acarbose with OISE or baicalein synergistically inhibited rat intestinal α-glucosidase. The combination index (CI) values for acarbose with OISE ranged from 0.33 to 0.75, suggesting a synergistic but not additive effect. OISE was determined to be a non-competitive inhibitor of maltose-hydrolyzing activity. In vivo, OISE were administered to normoglycemic and diabetic mice, either alone or in combination with acarbose. At doses between 50 and 200mgkg-1, OISE enhanced the efficacy of acarbose by up to 5-fold. These results demonstrated that OISE enhances the efficacy of acarbose in vivo, and that the combination of OISE and acarbose displayed a synergistic effect in vitro. Therefore, OISE can be used to design dietary supplements to treat diabetes.

Flavone C-glycosides from flowers of Trollius ledebouri.

The ethanol extract of the flowers of Trollius ledebouri yielded four flavone C-glycosides, 2''-O-vanilloylvitexin, 2''-O-feruloylorientin, 2''-O-beta-L-galactopyranosylvitexin, and 2''-O-beta-L-galactopyranosylorientin, along with known compounds, 6''-O-acetylorientin, 2''-O-(4'''-hydroxybenzoyl)vitexin, vitexin, and orientin. Their structures were elucidated by means of UV, IR, MS and NMR spectroscopic analyses.

[N01WA-735E, a human leukocyte elastase inhibitor from metabolites of microorganisms].

Human leukocyte elastase is an important selection target of inflammation and cancer. In this paper, a high throughput screening model was established for screening human leukocyte elastase inhibitors from thousands of strains of actinomycetes. As a result, a strain, N01WA-735 with potent suppression activity was isolated. Firstly, the strain N01WA-735 was identified as Streptomyces according to morphology and biochemical analysis. The Streptomyces N01WA-735 was processed by solvent extraction, silica column chromatography, Sephadex LH-20 column chromatography and crystallization to get a pure active compound named N01WA-735E. Its chemical structure was elucidated as the same as that of the compound named BE-52440A by physicochemical properties and spectral data of UV, MS, 1H-NMR and 13C-NMR respectively. The compound showed a strong inhibitory activity against human leukocyte elastase with IC50 of 3.02 micromol/L. The compound is reported as a human leukocyte elastase inhibitor for the first time.

[Establishment of a cell-based high-throughput screening model for PPARdelta agonists].

To establish a new high-throughput screening model for the agonist of PPARdelta, PPARdelta gene was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR), and subcloned to pGEM-T Vector for sequencing, then the PPARdelta fragment was excised by restriction enzymes, and inserted into pTARGET Vector to construct expression vector pTARGET-ppARdelta. Insert three copies of PPRE into pGl3-promoter vector to construct expression vector pGl3-PPRE x 3-luc. The vector pTARGET-ppARdelta was transiently cotransfected with pGl3-PPRE x 3-luc into different cell lines to assay the expression levels of luciferase. The PPARdelta agonist screening model was established and optimized. Bezafibrate and linoleic acid can induce the expression of luciferase significantly and in a dose-dependent manner. This method can be used for high throughput screening for the agonist of PPARdelta, which might become lead compounds for new anti-atheroscleriosis or anti-adiposity drugs.