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Phytase is an additive in animal feed that degrades phytic acid in plant material, reducing feeding costs, and pollution from fecal phosphorus excretion. A multistrategy approach was adopted to improve the expression of E. coli phytase in Pichia pastoris. We determined that the most suitable signal peptide for phytase secretion was an α-factor secretion signal with an initial enzyme activity of 153.51 U/mL. Increasing the copy number of this gene to four increased phytase enzyme activity by 234.35%. PDI overexpression and Pep4 gene knockout increased extracellular phytase production by 35.33% and 26.64%, respectively. By combining favorable factors affecting phytase expression and secretion, the enzyme activity of the phytase-engineered strain was amplified 384.60% compared with that of the original strain. We also evaluated the potential for the industrial production of the engineered strain using a 50-L fed-batch fermenter and achieved a total activity of 30,246 U/mL after 180 h of fermentation.

Curdlan is widely applied in the food and pharmaceutical industries. This review focuses on the biosynthetic pathways, regulatory mechanisms and metabolic engineering strategies for curdlan production. Firstly, curdlan biosynthesis is discussed. Furthermore, various strategies to increase curdlan production are summarized from four aspects, including the overexpression of genes for curdlan biosynthesis, weakening/knockdown of genes from competing pathways, increasing the supply of curdlan precursors, and optimization of fermentation conditions. Moreover, the emerging and advanced applications of curdlan are introduced. Finally, the challenges that are frequently encountered during curdlan biosynthesis are noted with a discussion of directions for curdlan production.

Vitamin K2 (menaquinone, MK) is an essential lipid-soluble vitamin with critical roles in blood coagulation and bone metabolism. Chemically, the term vitamin K2 encompasses a group of small molecules that contain a common naphthoquinone head group and a polyisoprenyl side chain of variable length. Among them, menaquinone-7 (MK-7) is the most potent form. Here, the biosynthetic pathways of vitamin K2 and different types of MK produced by microorganisms are briefly introduced. Further, we provide a new aspect of MK-7 production, which shares a common naphthoquinone ring and polyisoprene biosynthesis pathway, by analyzing strategies for expanding the product spectrum. We review the findings of metabolic engineering strategies targeting the shikimate pathway, polyisoprene pathway, and menaquinone pathway, as well as membrane engineering, which provide comprehensive insights for enhancing the yield of MK-7. Finally, the current limitations and perspectives of microbial menaquinone production are also discussed. This article provides in-depth information on metabolic engineering strategies for vitamin K2 production by expanding the product spectrum.

Porcine circovirus type 2 (PCV2) causes postweaning multisystemic wasting syndrome (PMWS) as well as other PCV-associated diseases (PCVADs), which seriously affect the development of the swine industry. The association between aberrant expression of microRNA-21 (miR-21) and the pathogenesis of inflammatory diseases is already known. Also, our previous study showed elevated ssc-miR-21-5p (miR-21) levels in PCV2-infected porcine kidney 15 (PK-15) cells. However, the functional expression of miR-21 in PCV2 infection is unknown. Here, we found that the miR-21 levels were substantially upregulated in PCV2-infected cells, while the expression of PDCD4 and a PDCD4-derived circRNA (circPDCD4) were downregulated compared with the noninfected cells. The results of RNA immunoprecipitation and dual-luciferase reporter (DLR) assay revealed that circPDCD4 acted as a miR-21 sponge and PDCD4 was a miR-21 target. Functionally, we found that miR-21 overexpression induced the NF-κB pathway along with inflammation in cells exposed to PCV2. Further, the overexpression of PDCD4 or circPDCD4 downregulated miR-21 levels and subsequently, attenuated the miR-21-induced activation of inflammation and the NF-κB pathway. Thus, PCV2 activated the NF-κB pathway and cellular inflammatory responses through regulating circPDCD4, miR-21, and PDCD4 in PK-15 cells.

Pseudorabies virus (PRV) accounts for a critical swine disease incurring economic losses worldwide. Several PRV vaccines are commercially available but these vaccines are effective against only certain prevalent PRV strains in China. To prevent PRV-induced latent infection and decrease the pathogenicity, novel anti-PRV drugs are required to prevent PRV infection. Natural products show exceptional structural diversity representing an important source for developing novel therapeutic agents. Quercetin is a flavonoid with anti-oxidant, anti-cancer, anti-bacterial and anti-viral activities. This study involved quercetin for studying the anti-PRV function in vitro and in vivo. Quercetin was found to significantly decrease the PRV virulent strain HNX at a half-maximal inhibitory concentration (IC50) of 2.618 μM and selectivity index 229. This anti-PRV activity of quercetin was found to be dose-dependent. Furthermore, quercetin also inhibited a wide the infections by a spectrum of PRV strains like HNX, Ea, Bartha and Fa strain. These virucidal effects of quercetin suggest the interaction between these molecules and viral particles, and quercetin is responsible for inhibiting the adsorption of PRV infections. The silico assays suggesting that quercetin might interact with the gD-protein on the surface of the PRV important for viral infection. Additional, the quercetin plantar injection protected the mice from the lethal challenge, decreasing the PRV-infected mice's brain viral loads and mortality. These results provides a anti-PRV strategy and contribute to drug discovery and development.

Phytases are enzymes that can hydrolyze phytate and its salts into inositol and phosphoric acid, and have been utilized to increase the availability of nutrients in animal feed and mitigate environmental pollution. However, the enzymes’low thermostability has limited their application during the feed palletization process. In this study, a combination of B-value calculation and protein surface engineering was applied to rationally evolve the heat stability of Escherichia coli phytase. After systematic alignment and mining for homologs of the original phytase from the histidine acid phosphatase family, the two models 1DKL and 1DKQ were chosen and used to identify the B-values and spatial distribution of key amino acid residues. Consequently, thirteen potential amino acid mutation sites were obtained and categorized into six domains to construct mutant libraries. After five rounds of iterative mutation screening, the thermophilic phytase mutant P56214 was finally yielded. Compared with the wild-type, the residual enzyme activity of the mutant increased from 20% to 75% after incubation at 90°C for 5 min. Compared with traditional methods, the rational engineering approach used in this study reduces the screening workload and provides a reference for future applications of phytases as green catalysts.

Phosphates are important components in the fermentation medium for biosurfactant production. In the present study, Ochrobactrum intermedium strain XY-1 was used as the experimental strain, the effects of various phosphates used in the biosurfactants fermentation media was preliminarily investigated on cell growth, and surface tension, and emulsifying activity of fermentation broth. Under the same total phosphorus concentration of 0.035 mol/L, KH2PO4 + Na2HPO4, KH2PO4, and Na2HPO4 was respectively used as the phosphorus source of biosurfactant fermentation at 30 °C and 160 rpm. The results showed that the bacteria grew slowly and the maximum emulsifying activity of fermentation broth reached 52.95% in the fermentation with KH2PO4 + Na2HPO4 as phosphorus source, and larger bacterial growth and 35.9% maximum emulsifying activity exhibited in the fermentation with KH2PO4, smaller bacterial growth and 24.54% maximum emulsifying activity exhibited in the fermentation with Na2HPO4. The phosphate mixture of KH2PO4 and Na2HPO4 benefits the biosurfactant fermentation by limiting the growth of Ochrobactrum intermedium strain XY-1, which might be the earliest report on the phosphorous source of biosurfactant fermentation by Ochrobactrum intermedium.

Novel Sr 3 Gd (1– x ) Dy x Na(PO 4 ) 3 F (SGNP: x Dy 3+ , x =0.01, 0.03, 0.05, 0.07, 0.09, 0.11) phosphors were synthesized by a conventional solid-state reaction method at different compositions. The X-ray diffraction results confirmed that the as-prepared samples were pure phase. The phosphor had two intense emission bands centering at 481 and 574 nm which could be attributed to the 4 F 9/2 → 6 H 15/2 transition and the 4 F 9/2 → 6 H 13/2 transition, respectively. The chromaticity coordinates ( x, y ) of this phosphor were calculated to be (0.3054, 0.3354) located on the region of white light region when excited at 350 nm. The concentration quenching mechanism of Dy 3+ was ascribed to the dipole-dipole interaction. The current research suggested that the phosphors might be potential application in the w-LEDs.

For the last decade, porcine epidemic diarrhea virus (PEDV) variant strains have caused severe damage to the global pig industry. Until now, no effective antivirals have been developed for the therapeutic treatment of PEDV infection. In the present study, we found that quercetin significantly suppressed PEDV infection at noncytotoxic concentrations. A molecular docking study indicated that quercetin might bind the active site and binding pocket of PEDV 3C-like protease (3CLpro). Surface plasmon resonance (SPR) analysis revealed that quercetin exhibited a binding affinity to PEDV 3CLpro. Based on the results of the fluorescence resonance energy transfer (FRET) assay, quercetin was proven to exert an inhibitory effect on PEDV 3CLpro. Since coronavirus 3CLpro is an important drug target and participates in the viral replication process, quercetin should be developed as a novel drug in the control of PEDV infection.

Ba3Lu(PO4)3:Dy3+ phosphors were successfully synthesized by conventional solid state reaction and its photoluminescence properties were investigated by X-ray diffraction (XRD), photoluminescence spectra and diffuse reflectance spectra, respectively. Results showed that the phosphor could be excited by the ultraviolet visible light in the region from 320 to 460 nm, and it showed two dominant emission bands peaking at 484 nm (blue light) and 575 nm (yellow light) which originated from the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, respectively. According to Dexter's theory, the concentration quenching mechanism occurred via the electric dipole-dipole interaction. The lifetime values of Dy3+ ions at different concentrations (x=0.01, 0.03, 0.05, 0.08 and 0.10) were determined to be about 0.8556, 0.7595, 0.6864, 0.6059 and 0.5456 ms.

An obligately thermophilic strain ZY-10 was isolated from the crude oil in a high-temperature oilfield, which was capable of degrading heavy crude oil. Phenotypic and phylogenetic analysis demonstrated that the isolate should be grouped in the genus Geobacillus, which shared the highest similarity (99%) of the 16S rDNA sequence to Geobacillus stearothermophilus. However, the major cellular fatty acid iso-15:0 (28.55%), iso-16:0 (24.93%), iso-17:0 (23.53%) and the characteristics including indole production, tolerance to NaN3 and carbohydrate fermentation showed some difference from the recognized species in the genus Geobacillus. The isolate could use tridecane, hexadecane, octacosane and hexatridecane as sole carbon source for cell growth, and the digesting rate of long-chain alkane was lower than that of short-chain alkane. When the isolate was cultured in the heavy crude oil supplement with inorganic salts and trace yeast extract, the concentration of short-chain alkane was significantly increased and the content of long-chain alkane was decreased, suggesting that the larger hydrocarbon components in crude oil were degraded into shorter-chain alkane. Strain ZY-10 would be useful for improving the mobility of crude oil and upgrading heavy crude oil in situ.

Biofitration was successfully applied to treat air streams containing a mixture of ethyl acetate and toluene. The experiment was performed by two identical bench-scale biofilters, which were acclimated by ethyl acetate and toluene, respectively. During a 3 month steady-state performance, the two biofilters showed equivalent elimination capacity (EC) for toluene (50 g/m 3 bed/h of pure toluene). However, the biofilter acclimated with ethyl acetate showed a much higher EC for ethyl acetate (400 g/m 3 bed/h of pure ethyl acetate) than that acclimated with toluene (250 g/m 3 bed/h). The concurrent biofiltration of toluene was inhibited by the presence of ethyl acetate. The results also showed that more nitrogen and phosphorus were consumed in the process of the biofiltration of toluene compared with the treatment of ethyl acetate. After the 3 month experiment, the pH of the media treating ethyl acetate dropped from 6.71 to 5.50, whereas the pH of the media treating toluene increased from 6.71 to 7.08.

Toluene vapour was degraded in a biofilter packed with various initial moisture contents of packing materials at 650–1000 mg (toluene)/m3 (gas) and 24.0–36.8 g/m3/h load. The results demonstrated that a higher degradation capacity (DC) could be reached within a shorter operation time at a higher initial moisture content. During 144 h operation, the maximal degradation rate (DR) and degradation capacity (DC) were, respectively, 60%, 20 g/m3/h for 30 and 40% initial moisture content. For 60 and 70% initial moisture content, the DR and DC could be higher at the beginning of operation, which were above 70% and 20 g/m3/h, and reached the maximum of 100% and above 25–30 g/m3/h at about 75 h operation. The microbial determination results of packing materials (30, 50 and 70% initial moisture content) in biofilter operating for 144 h showed that the initial moisture content of packing materials would affect the numbers and types of microbial community of packing materials. With the increase in the initial moisture content, the quantity of moulds and actinomyces would decrease and the number of bacteria would increase. The packing material with 50% initial moisture content was beneficial to the yeast growth.

An efficient and highly enantioselective synthesis of 3-hydroxy-4-phenylbutan-2-one was developed involving the asymmetric epoxidation of an enone and hydrogenolysis of an α,β-epoxyketone. 1-Phenyl...

An efficient three-step synthesis of nonenolide (V), a lactose with coconut-like and rancid odour, is given.

KLa (MoO 4 ) 2 : Eu 3 + phosphors were prepared by the hydrothermal method. The after tuning of synthesis time and the ratio of the ethylene glycol to water ratio made the phosphor present different morphologies, including peanut-like shape and spheres. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), diffuse reflectance spectrum, and fluorescence spectrum. Under the excitation of 397 nm near-ultraviolet, the typical red emission produced by Eu 3 + ions can be observed. And the phosphors show strong red light around 612 nm, attributed to 5 D 0 → 7 F 2 transition of Eu 3 + ion. The luminescence properties of the as-prepared phosphors were studied based on changing the synthesis condition. It is found that the synthesis time and the changing of the ratio of ethylene glycol to water play the crucial role in the formation of morphology. The optimum dopant concentration of Eu 3 + ions in KLa (MoO 4 ) 2 : Eu 3 + is around 7 mol. %. Moreover, the fluorescence decay curve and thermal stability of luminescence were also investigated in detail. The Commission International de I’Eclairage coordinates of KLa (MoO 4 ) 2 : 0.07Eu 3 + located in the red reddish region. All the results suggest that KLa (MoO 4 ) 2 : 0.07Eu 3 + might be a promising reddish-orange emitting phosphor used in white light-emitting diodes (w-LED).

Trichosporon fermentans cells with intracellular lipase was permeabilized with cell permeabilization agents. The optimum conditions of permeabilization were determined and then permeabilization methods were compared, as well as preservation stability of permeabilized cells was tested. The optimum permeabilization condition of various permeabilization agents were that cells were permeabilized with 2% methylbenzene for 40min, 2% chloroform for 10min and 25% acetone for 40min. The maximum intracellular lipase activity of permeabilized cells was achieved which was prepared with 2% chloroform for 10min and then dried, and kept stable within preservation period of 30 days.

With respect to the food safety and quality, it is necessary to isolate and apply protective microbes for food preservation. Lactic acid bacteria can produce some antimicrobial substances by metabolism, which are related with biological preservation of foods. Lactobacillus brevis P-319 is a strain isolated from sauerkraut. Antimicrobial activity of Lactobacillus brevis P-319 cell-free broth was studied under some conditions of food processing and preservation. Incubating the cell-free broth in the presence of trypsin and papain resulted in loss of antimicrobial activity of the cell-free broth, which demonstrated the substance with antimicrobial activity might have the molecular structure of protein or peptide. The cell-free broth kept at 100°C or at pH 2.0∼6.0 for 2 h or under natural conditions for four weeks still displayed antimicrobial activity. No loss in antimicrobial activity of the cell-free broth was observed after treatment with ethanol below 8% and NaCl below 6%, but significant reduction after incubation in the presence of 8% NaCl. Lactobacillus brevis P-319 can be considered to have commercial potential, applied perspectives for food manufacture and chemical preservatives in foods.

Reddish-orange emitting phosphors, Sr 3 Gd(PO 4 ) 3 : Sm 3+ , were successfully synthesized by a conventional solid-state reaction. The crystal structure of the phosphors was characterized by x-ray diffraction. The excitation spectra and emission spectra were utilized to characterize the luminescence properties of the as-prepared phosphors. The results show that the phosphor consisted of some sharp emission peaks of Sm 3+ ions centered at 564, 600, 647, and 707 nm, respectively. The critical distance of Sr 3 Gd 0.93 (PO 4 ) 3 : 0.07Sm 3+ was calculated to be 19.18 Å and the lifetime value of the sample was 1.63 ms. The band gap of Sr 3 Gd(PO 4 ) 3 was estimated to be about 2.74 eV from the diffuse reflection spectrum. The optimum doping concentration is 7 mol. % and the quenching occurs via dipole–dipole interaction according to Dexter’s theory. The Commission Internationale de L’Eclairage value of Sr 3 Gd(PO 4 ) 3 : Sm 3+ phosphors presented that it has high color purity. These results indicated that the Sr 3 Gd(PO 4 ) 3 : Sm 3+ may be a promising reddish-orange emitting phosphor for cost-effective near ultraviolet white light-emitting diodes.

An efficient and highly enantioselective synthesis of 3-hydroxy-4-phenylbutan-2-one was developed involving the asymmetric epoxidation of an enone and hydrogenolysis of an α,β-epoxyketone. 1-Phenyl-3-buten-2-one was epoxidised with t-butyl hydroperoxide using a chiral La-BINOL-Ph3P=O complex as the catalyst to give ( 3S,4R)- or ( 3R,4S)-3,4-epoxy-4-phenylbutan-2-one in ~90% yield and 97% ee. The resultant optically active epoxyketone was reduced in the presence of Pd/C (5 mol%) and H2 (3 bar) in THF at room temperature to produce ( S)- or ( R)-3-hydroxy-4-phenylbutan-2-one in ~80% yield with more than 90% enantiomeric excess.

A three-step synthesis of 2-nonen-4-olide starting from heptanal is reported. (E)-3-Nonenoic acid, prepared by Knoevenagel condensation of malonic acid and heptanal, was oxidised by performic acid, a process accompanied by lactonisation, to give 3-hydroxynonan-4-olide in 85% yield. This lactone when reacted with MsCl in the presence of Et3N gave, by elimination, 2-nonen-4-olide in 88% yield. The overall yield was 75%. The odour of the product was evaluated by GC-olfactory analysis and sniffing blotter confirming an oily, coconut-like, and rancid odour.