首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
BackgroundPoly(dl-lactic acid), or PDLLA, is a biodegradable polymer that can be hydrolyzed by various types of enzymes. The protease produced by Actinomadura keratinilytica strain T16-1 was previously reported to have PDLLA depolymerase activity. However, few studies have reported on PDLLA-degrading enzyme production by bacteria. Therefore, the aims of this study were to determine a suitable immobilization material for PDLLA-degrading enzyme production and optimize PDLLA-degrading enzyme production by using immobilized A. keratinilytica strain T16-1 under various fermentation process conditions in a stirrer fermenter.ResultsAmong the tested immobilization materials, a scrub pad was the best immobilizer, giving an enzyme activity of 30.03 U/mL in a shake-flask scale. The maximum enzyme activity was obtained at aeration 0.25 vvm, agitation 170 rpm, 45°C, and 48 h of cultivation time. Under these conditions, a PDLLA-degrading enzyme production of 766.33 U/mL with 15.97 U/mL·h productivity was observed using batch fermentation in a 5-L stirrer fermenter. Increased enzyme activity and productivity were observed in repeated-batch (942.67 U/mL and 19.64 U/mL·h) and continuous fermentation (796.43 U/mL and 16.58 U/mL·h) at a dilution rate of 0.013/h. Scaled-up production of the enzyme in a 10-L stirrer bioreactor using the optimized conditions showed a maximum enzyme activity of 578.67 U/mL and a productivity of 12.06 U/mL·h.ConclusionsThis research successfully scaled-up the enzyme production to 5 and 10 L in a stirrer fermenter and is helpful for many applications of poly(lactic acid).  相似文献   

2.
BackgroundIron magnetic nanoparticles have attracted much attention. They have been used in enzyme immobilization because of their properties such as product is easily separated from the medium by magnetic separation. The present work was designed to immobilize horseradish peroxidase on Fe3O4 magnetic nanopraticles without modification.ResultsIn the present study, horseradish peroxidase (HRP) was immobilized on non-modified Fe3O4 magnetic nanoparticles. The immobilized HRP was characterized by FT-IR spectroscopy, scanning electron microscopy, and energy dispersive X-ray. In addition, it retained 55% of its initial activity after 10 reuses. The optimal pH shifted from 7.0 for soluble HRP to 7.5 for the immobilized HRP, and the optimal temperature shifted from 40°C to 50°C. The immobilized HRP is more thermostable than soluble HRP. Various substrates were oxidized by the immobilized HRP with higher efficiencies than by soluble HRP. Km values of the soluble and immobilized HRP were 31 and 45 mM for guaiacol and 5.0 and 7.0 mM for H2O2, respectively. The effect of metals on soluble and immobilized HRP was studied. Moreover, the immobilized HRP was more stable against high concentrations of urea, Triton X-100, and isopropanol.ConclusionsPhysical immobilization of HRP on iron magnetic nanoparticles improved the stability toward the denaturation induced by pH, heat, metal ions, urea, detergent, and water-miscible organic solvent.  相似文献   

3.
BackgroundCyclodextrin glucanotransferase (CGTase) from Amphibacillus sp. NPST-10 was covalently immobilized onto amino-functionalized magnetic double mesoporous core–shell silica nanospheres (mag@d-SiO2@m-SiO2-NH2), and the properties of the immobilized enzyme were investigated. The synthesis process of the nanospheres included preparing core magnetic magnetite (Fe3O4) nanoparticles, coating the Fe3O4 with a dense silica layer, followed by further coating with functionalized or non-functionalized mesoporous silica shell. The structure of the synthesized nanospheres was characterized using TEM, XRD, and FT-IR analyses. CGTase was immobilized onto the functionalized and non-functionalized nanospheres by covalent attachment and physical adsorption.ResultsThe results indicated that the enzyme immobilization by covalent attachment onto the activated mag@d-SiO2@m-SiO2-NH2, prepared using anionic surfactant, showed highest immobilization yield (98.1%), loading efficiency (96.2%), and loading capacity 58 µg protein [CGTase]/mg [nanoparticles]) which were among the highest yields reported so far for CGTase. Compared with the free enzyme, the immobilized CGTase demonstrated a shift in the optimal temperature from 50°C to 50–55°C, and showed a significant enhancement in the enzyme thermal stability. The optimum pH values for the activity of the free and immobilized CGTase were pH 8 and pH 8.5, respectively, and there was a significant improvement in pH stability of the immobilized enzyme. Moreover, the immobilized CGTase exhibited good operational stability, retaining 56% of the initial activity after reutilizations of ten successive cycles.ConclusionThe enhancement of CGTase properties upon immobilization suggested that the applied nano-structured carriers and immobilization protocol are promising approach for industrial bioprocess for production of cyclodextrins using immobilized CGTase.  相似文献   

4.
BackgroundGABA (γ-aminobutyric acid) is a four-carbon nonprotein amino acid that has hypotensive, diuretic, and tranquilizing properties. Glutamate decarboxylase (GAD) is the key enzyme to generate GABA. A simple and economical method of preparing and immobilizing GAD would be helpful for GABA production. In this study, the GAD from Lactobacillus fermentum YS2 was expressed under the control of a stress-inducible promoter and was purified and immobilized in a fusion form, and its reusability was investigated.ResultsThe fusion protein CBM-GAD was expressed in Escherichia coli DH5α carrying pCROCB-gadB, which contained promoter PrpoS, cbm3 (family 3 carbohydrate-binding module from Clostridium thermocellum) coding sequence, the gadB gene from L. fermentum YS2 coding for GAD, and the T7 terminator. After a one-step purification of CBM-GAD using regenerated amorphous cellulose (RAC) as an adsorbent, SDS-PAGE analysis revealed a clear band of 71 kDa; the specific activity of the purified fusion protein CBM-GAD reached 83.6 ± 0.7 U·mg-1. After adsorption onto RAC, the immobilized GAD with CBM3 tag was repeatedly used for GABA synthesis. The protein-binding capacity of RAC was 174 ± 8 mg·g-1. The immobilized CBM-GAD could repeatedly catalyze GABA synthesis, and 8% of the initial activities was retained after 10 uses. We tested the conversion of monosodium glutamate to GABA by the immobilized enzyme; the yield reached 5.15 g/L and the productivity reached 3.09 g/L·h.ConclusionsRAC could be used as an adsorbent in one-step purification and immobilization of CBM-GAD, and the immobilized enzyme could be repeatedly used to catalyze the conversion of glutamate to GABA.  相似文献   

5.
BackgroundThe selection of new yeast strains could lead to improvements in bioethanol production. Here, we have studied the fermentative capacity of different auxotrophic mutants of Saccharomyces cerevisiae, which are routinely used as hosts for the production of heterologous proteins. It has recently been found that these strains exhibit physiological alterations and peculiar sensitivities with respect to the parental prototrophic strains from which they derive. In this work the performance of auxotrophic S. cerevisiae CEN.PK strains was compared to the corresponding prototrophic strain, to S. cerevisiae T5bV, a strain isolated from grape must and to another auxotrophic strain, S. cerevisiae BY4741.ResultsThe results indicate that the fermentative capacity of strains grown in 2% glucose was similar in all the strains tested. However, in 15% initial glucose, the auxotrophic strains exhibited a more than doubled ethanol yield on biomass (10 g g- 1dw) compared to the prototrophic strains (less than 5 g g- 1dw). Other tests have also evidenced that in medium depletion conditions, ethanol production continues after growth arrest.ConclusionsThe results highlight the capacity of auxotrophic yeast strains to produce ethanol per mass unit, in a higher amount with respect to the prototrophic ones. This leads to potential applications for auxotrophic strains of S. cerevisiae in the production of ethanol in both homogeneous and heterogeneous phases (immobilized systems). The higher ethanol yield on biomass would be advantageous in immobilized cell systems, as a reduced yeast biomass could greatly reduce the mass transfer limitations through the immobilization matrix.  相似文献   

6.
BackgroundIn biodegradation processes free enzymes often undergo deactivation. Thus, it is very important to obtain highly stable enzymes by different methods. Immobilization allows for successful stabilization of many multimeric enzymes by increasing the rigidity of the enzyme structure. This study aimed to evaluate some environmental factors that affect catechol 1,2-dioxygenase from Stenotrophomonas maltophilia KB2 immobilized in alginate hydrogel. The goal of the present work was to improve the functional stability of the enzyme by increasing its structural rigidity.ResultsImmobilization yield and expressed activity were 100% and 56%, respectively. Under the same storage conditions, the activity of the immobilized enzyme was still observed on the 28th d of incubation at 4°C, whereas the free enzyme lost its activity after 14 d. The immobilized enzyme required approximately 10°C lower temperature for its optimal activity than the free enzyme. Immobilization shifted the optimal pH from 8 for the soluble enzyme to 7 for the immobilized enzyme. The immobilized catechol 1,2-dioxygenase showed activity against 3-methylcatechol, 4-methylcatechol, 3-chlorocatechol, 4-chlorocatechol, and 3,5-dichlorocatechol. The immobilization of the enzyme promoted its stabilization against any distorting agents: aliphatic alcohols, phenols, and chelators.ConclusionsThe entrapment of the catechol 1,2-dioxygenase from S. maltophilia KB2 has been shown to be an effective method for improving the functional properties of the enzyme. Increased resistance to inactivation by higher substrate concentration and other factors affecting enzyme activity as well as broadened substrate specificity compared to the soluble enzyme, makes the immobilized catechol 1,2-dioxygenase suitable for the bioremediation and detoxification of xenobiotic-contaminated environments.  相似文献   

7.
BackgroundXylanases and β-d-xylosidases are the most important enzymes responsible for the degradation of xylan, the second main constituent of plant cell walls.ResultsIn this study, the main extracellular xylanase (XYL I) and β-xylosidase (BXYL I) from the fungus Penicillium janczewskii were purified, characterized and applied for the hydrolysis of different substrates. Their molecular weights under denaturing and non-denaturing conditions were, respectively, 30.4 and 23.6 kDa for XYL I, and 100 and 200 kDa for BXYL I, indicating that the latter is homodimeric. XYL I is highly glycosylated (78%) with optimal activity in pH 6.0 at 65°C, while BXYL I presented lower sugar content (10.5%) and optimal activity in pH 5.0 at 75°C. The half-lives of XYL I at 55, 60 and 65°C were 125, 16 and 6 min, respectively. At 60°C, BXYL I retained almost 100% of the activity after 6 h. NH4+, Na+, DTT and β-mercaptoethanol stimulated XYL I, while activation of BXYL I was not observed. Interestingly, XYL I was only partially inhibited by Hg2 +, while BXYL I was completely inhibited. Xylobiose, xylotriose and larger xylooligosaccharides were the main products from xylan hydrolysis by XYL I. BXYL I hydrolyzed xylobiose and larger xylooligosaccharides with no activity against xylans.ConclusionThe enzymes act synergistically in the degradation of xylans, and present industrial characteristics especially in relation to optimal activity at high temperatures, prolonged stability of BXYL I at 60°C, and stability of XYL I in wide pH range.  相似文献   

8.
BackgroundDepletion of petroleum resources has enforced the search for alternative sources of renewable energy. Introduction of biofuels into the market was expected to become a solution to this disadvantageous situation. Attempts to cover fuel demand have, however, caused another severe problem—the waste glycerol generated during biodiesel production at a concentration of approximately 10% w/w. This, in turn, prompted a global search for effective methods of valorization of the waste fraction of glycerol.ResultsUtilization of the waste fraction at 48 h with an initial glycerol concentration of 30 g·L-1 and proceeding with 62% efficiency enabled the production of 9 g·L-1 dihydroxyacetone at 50% substrate consumption. The re-use of the immobilized biocatalyst resulted in a similar concentration of dihydroxyacetone (8.7 g·L-1) in two-fold shorter time, with an efficiency of 85% and lower substrate consumption (35%).ConclusionsThe method proposed in this work is based on the conversion of waste glycerol to dihydroxyacetone in a reaction catalyzed by immobilized Gluconobacter oxydans cell extract with glycerol dehydrogenase activity, and it could be an effective way to convert waste glycerol into a valuable product.  相似文献   

9.
BackgroundRice is globally one of the most important food crops, and NaCl stress is a key factor reducing rice yield. Amelioration of NaCl stress was assessed by determining the growth of rice seedlings treated with culture supernatants containing 5-aminolevulinic acid (ALA) secreted by strains of Rhodopseudomonas palustris (TN114 and PP803) and compared to the effects of synthetic ALA (positive control) and no ALA content (negative control).ResultsThe relative root growth of rice seedlings was determined under NaCl stress (50 mM NaCl), after 21 d of pretreatment. Pretreatments with 1 μM commercial ALA and 10X diluted culture supernatant of strain TN114 (2.57 μM ALA) gave significantly better growth than 10X diluted PP803 supernatant (2.11 μM ALA). Rice growth measured by dry weight under NaCl stress ordered the pretreatments as: commercial ALA > TN114 > PP803 > negative control. NaCl stress strongly decreased total chlorophyll of the plants that correlated with non-photochemical quenching of fluorescence (NPQ). The salt stress also strongly increased hydrogen peroxide (H2O2) concentration in NaCl-stressed plants. The pretreatments were ordered by reduction in H2O2 content under NaCl stress as: commercial ALA > TN114 > PP803 > negative control. The ALA pretreatments incurred remarkable increases of total chlorophyll and antioxidative activities of catalase (CAT), ascorbate peroxide (APx), glutathione reductase (GR) and superoxide dismutase (SOD); under NaCl stress commercial ALA and TN114 had generally stronger effects than PP803.ConclusionsThe strain TN114 has potential as a plant growth stimulating bacterium that might enhance rice growth in saline paddy fields at a lower cost than commercial ALA.  相似文献   

10.
BackgroundThe paper reports on the utilization of palm kernel oil (PKO) as a low cost renewable substrate for medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA) production by Pseudomonas putida BET001. Investigation on the effects of selected key variables on growth, mixed free fatty acids consumption and mcl-PHA production by the bacterial culture in the shaken flask system were carried out along with its kinetic modeling.ResultsThe biomass production, fatty acids consumption and mcl-PHA production were found favorable when the strain was cultured in mineral medium at pH 6–7, 28°C, aeration surface-to-volume ratio of 0.4 × 106 m- 1, 250 rpm agitation rate for 48 h. Mcl-PHA production by this strain showed mixed growth and non-growth associated components as described by Luedeking–Piret kinetic model.ConclusionThe findings of this study provided add to the literature on key variables in for achieving good microbial growth and mcl-PHA production in shake flasks culture. In addition, suitable kinetic model to describe cultivation in this system was also presented.  相似文献   

11.
BackgroundEndophytic bacteria are ubiquitous in all plant species contributing in host plant's nutrient uptake and helping the host to improve its growth. Moringa peregrina which is a medicinal plant, growing in arid region of Arabia, was assessed for the presence of endophytic bacterial strains.ResultsPCR amplification and sequencing of 16S rRNA of bacterial endophytes revealed the 5 endophytic bacteria, in which 2 strains were from Sphingomonas sp.; 2 strains from Bacillus sp. and 1 from Methylobacterium genus. Among the endophytic bacterial strains, a strain of Bacillus subtilis LK14 has shown significant prospects in phosphate solubilization (clearing zone of 56.71 mm after 5 d), ACC deaminase (448.3 ± 2.91 nM α-ketobutyrate mg- 1 h- 1) and acid phosphatase activity (8.4 ± 1.2 nM mg- 1 min- 1). The endophytic bacteria were also assessed for their potential to produce indole-3-acetic acid (IAA). Among isolated strains, the initial spectrophotometry analysis showed significantly higher IAA production by Bacillus subtilis LK14. The diurnal production of IAA was quantified using multiple reactions monitoring method in UPLC/MS–MS. The analysis showed that LK14 produced the highest (8.7 μM) IAA on 14th d of growth. Looking at LK14 potentials, it was applied to Solanum lycopersicum, where it significantly increased the shoot and root biomass and chlorophyll (a and b) contents as compared to control plants.ConclusionThe study concludes that using endophytic bacterial strains can be bio-prospective for plant growth promotion, which might be an ideal strategy for improving growth of crops in marginal lands.  相似文献   

12.
BackgroundSulphur-oxidizing microorganisms are widely used in the biofiltration of total reduced sulphur compounds (odorous and neurotoxic) produced by industries such as the cellulose and petrochemical industries, which include high-temperature process steps. Some hyperthermophilic microorganisms have the capability to oxidize these compounds at high temperatures (> 60°C), and archaea of this group, for example, Sulfolobus metallicus, are commonly used in biofiltration technology.ResultsIn this study, a hyperthermophilic sulphur-oxidizing strain of archaea was isolated from a hot spring (Chillán, Chile) and designated as M1. It was identified as archaea of the genus Sulfolobus (99% homology with S. solfataricus 16S rDNA). Biofilms of this culture grown on polyethylene rings showed an elemental sulphur oxidation rate of 95.15 ± 15.39 mg S l-1 d-1, higher than the rate exhibited by the biofilm of the sulphur-oxidizing archaea S. metallicus (56.8 ± 10.91 mg l-1 d-1).ConclusionsThe results suggest that the culture M1 is useful for the biofiltration of total reduced sulphur gases at high temperatures and for other biotechnological applications.  相似文献   

13.
BackgroundThe yield of almonds [Prunus dulcis (Mill.) D.A. Webb] could be low due to climatic problems and any factor improving kernel size and weight, such as the use of plant bioregulators (PBRs), should be beneficial.ResultsThree plant bioregulators: 24-epibrassinolide (BL), gibberellic acid (GA3) and kinetin (KN) were applied at three spray concentrations to Non Pareil and Carmel cultivars, at two phenological stages during bloom, in the 2014 and 2015 seasons. The results showed significant differences (P < 0.0001). For total dry weight of Non Pareil, the best treatment was BL (30 mg·L-1), with an average of 1.45 g, while the control was 1.30 g, at pink button during 2015. For Carmel, the best dry weight was 1.23 g, achieved with BL (30 mg·L-1) at fallen petals in both seasons. The average dry weight of the controls varied between 1.13 and 1.18 g. The greatest almond lengths and widths in Non Pareil were 24.98 mm and 15.05 mm, achieved with BL (30 mg·L-1) and KN (50 μL·L-1) treatments, respectively, applied at pink button in 2015. In Carmel, the greatest length and width were 24.38 and 13.44 mm, obtained with BL (30 mg·L-1) applied at the stages of pink button and fallen petals, respectively, in 2015. The control reached lengths between 22.33 and 23.38 mm, and widths between 11.99 and 12.93 mm.ConclusionsThe use of the bioregulators showed significant favorable effects on dry weight, length and width of kernels at harvest, in both cultivars.  相似文献   

14.
BackgroundThe effect of diverse oxygen transfer coefficient on the l-erythrulose production from meso-erythritol by a newly isolated strain, Gluconobacter kondonii CGMCC8391 was investigated. In order to elucidate the effects of volumetric mass transfer coefficient (kLa) on the fermentations, baffled and unbaffled flask cultures, and fed-batch cultures were developed in present work.ResultsWith the increase of the kLa value in the fed-batch culture, l-erythrulose concentration, productivity and yield were significantly improved, while cell growth was not the best in the high kLa. Thus, a two-stage oxygen supply control strategy was proposed, aimed at achieving high concentration and high productivity of l-erythrulose. During the first 12 h, kLa was controlled at 40.28 h-1 to obtain high value for cell growth, subsequently kLa was controlled at 86.31 h-1 to allow for high l-erythrulose accumulation.ConclusionsUnder optimal conditions, the l-erythrulose concentration, productivity, yield and DCW reached 207.9 ± 7.78 g/L, 6.50 g/L/h, 0.94 g/g, 2.68 ± 0.17 g/L, respectively. At the end of fermentation, the l-erythrulose concentration and productivity were higher than those in the previous similar reports.  相似文献   

15.
BackgroundThree oligosaccharides (EOS, WOS and SOS) were respectively prepared from the corresponding polysaccharides, namely exopolysaccharide (EPS), water-extracted mycelial polysaccharide (WPS) and sodium hydroxide-extracted mycelial polysaccharides (SPS) from the endophytic fungus Fusarium oxysporum Dzf17. In this study, the effects of EOS, WOS and SOS on the activities of the defense-related enzymes, namely phenylalanine ammonia lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD) in its host plant Dioscorea zingiberensis cultures were investigated.ResultsFor the suspension cell cultures of D. zingiberensis, the highest PAL activity was induced by 0.5 mg/mL of WOS at 48 h after treatment, which was 4.55-fold as that of control. Both PPO and POD activities were increased to the maximum values by 0.25 mg/mL of WOS at 48 h after treatment, which were respectively 3.74 and 3.45-fold as those of control. For the seedling cultures, the highest PAL activity was elicited by 2.5 mg/mL of EOS at 48 h after treatment, which was 3.62-fold as that of control. Both PPO and POD reached their maximum values treated with 2.5 mg/mL of WOS at 48 h after treatment, which were 4.61 and 4.19-fold as those of control, separately.ConclusionsBoth EOS and WOS significantly increased the activities of PAL, PPO and POD in the suspension cell and seedling cultures of D. zingiberensis. The results suggested that the oligosaccharides from the endophytic fungus F. oxysporum Dzf17 may be related to the activation and enhancement of the defensive mechanisms of D. zingiberensis suspension cell and seedling cultures.  相似文献   

16.
BackgroundLiquid wax esters are widely used in cosmetic as well as pharmaceutical and other industries. The demand of organic and natural products is increasing nowadays. Coconut oil contains benefit fatty acids and has been mainly used for oil-based and moisturizer products. Liquid wax esters from coconut oil and unsaturated fatty alcohol can be synthesized by enzymatic reaction; and it is interesting for using as an alternative natural ingredient in these industries.ResultsOptimal condition for coconut oil based wax ester synthesis by immobilized lipase EQ3 was 10 U of enzyme, temperature at 30°C and molar ratio of coconut oil to oleyl alcohol at 1:3 (mol/mol) (0.33X) dissolved in isooctane for 12 h, while for Lipozyme RM IM optimal condition was 10 U of enzyme, temperature at 45°C and oil/alcohol molar ratio at 1:3 (0.33X) dissolved in isooctane for 3 h. Percentage of wax esters synthesized by both lipases reached more than 88%. Both immobilized lipases catalyzed high yield of wax esters within the 2nd batch; after that, the immobilized lipases showed reduced activity and synthesized < 60% of wax esters from the 3rd to 5th batch. The main composition of wax esters was ~ 48% oleyl laurate with 10% degradation at ~ 250°C.ConclusionsThe liquid wax ester synthesis by commercial Lipozyme RM IM had higher effect than immobilized lipase EQ3, but both catalysts were stable within 2 batches in the optimum condition. The characteristic properties of wax esters showed potential for use as components in cosmetics and skin care products.How to citeUngcharoenwiwat P, H-Kittikun A. Enzymatic synthesis of coconut oil based wax esters by immobilized lipase EQ3 and commercial lipozyme RMIM. Electron J Biotechnol 2020;47. https://doi.org/10.1016/j.ejbt.2020.06.005  相似文献   

17.
BackgroundA simple, rapid, low-cost and environmentally friendly method was developed to determine dopamine (DA) in the presence of ascorbic (AA) and uric acid (UA) based on a novel technique to prepare a graphene–chitosan (GR–CS) nanocomposite and modify it on the surface of carbon paste electrode (CPE). For our design, CS acts as a media to disperse and stabilize GR, and then GR plays a key role to selective and sensitive determination of DA.ResultsUnder physiological conditions, the linear range for dopamine was determined from 1 × 10- 4 to 2 × 10- 7 mol/L with a good correlation coefficient of 0.9961 in the presence of 1000-fold interference of AA and UA. The detection limit was estimated to be 9.82 × 10- 8 mol/L (S/N = 3). In order to study the stability and reproducibility, GR/CS/CPE underwent successive measurements in 10 times and then tested once a d for 30 d. The result exhibited 98.25% and 91.62% activities compared with the original peak current after 10-time measurements and 30-d storage.ConclusionThe GR/CS/CPE has wide linear concentration range, low detection limit, and good reproducibility and stability, which suggests that our investigations provide a promising alternative for clinic DA determination.  相似文献   

18.
BackgroundTreating latex rubber sheet wastewater often leads to the generation of a rotten-egg odor from toxic H2S. To increase the treatment efficiency and eliminate H2S, purple nonsulfur bacteria (PNSB), prepared by supplementing non-sterile rubber sheet wastewater (RAW) with fermented pineapple extract (FPE), were used to treat this wastewater under microaerobic light conditions. The following 3 independent variables: chemical oxygen demand (COD), initial pH and FPE dose were investigated using the Box–Behnken design to find optimal conditions for stimulating the growth of indigenous PNSB (PNSBsi).ResultsThe addition of 2.0% FPE into RAW, which had a COD of 2000 mg L- 1 and an initial pH of 7.0, significantly decreased oxidation reduction potential (ORP) value and stimulated PNSBsi to reach a maximum of 7.8 log cfu mL- 1 within 2 d. Consequently, these PNSBsi, used as inoculants, were investigated for their ability to treat the wastewater under microaerobic light conditions. A central composite design was used to determine the optimal conditions for the wastewater treatment. These proved to be 7% PNSBsi, 0.8% FPE and 4 d retention time and this combination resulted in a reduction of 91% for COD, 75% for suspended solids, 61% for total sulfide while H2S was not detected. Results of abiotic control and treatment sets indicated that H2S was produced by heterotrophic bacteria and it was then effectively deactivated by PNSBsi.ConclusionsThe stimulation of PNSB growth by FPE under light condition was to lower ORP, and PNSBsi proved to be effective for treating the wastewater.  相似文献   

19.
BackgroundCatalase (CAT) is an important enzyme that degrades H2O2 into H2O and O2. To obtain an efficient catalase, in this study, a new strain of high catalase-producing Serratia marcescens, named FZSF01, was screened and its catalase was purified and characterized.ResultsAfter optimization of fermentation conditions, the yield of catalase produced by this strain was as high as 51,468 U/ml. This catalase was further purified using two steps: DEAE-fast flow and Sephedex-G150. The purified catalase showed a specific activity of 197,575 U/mg with a molecular mass of 58 kDa. This catalase exhibited high activity at 20–70°C and pH 5.0–11.0. Km of the catalase was approximately 68 mM, and Vmax was 1886.8 mol/min mg. This catalase was further identified by LC–MS/MS, and the encoding gene was cloned and expressed in Escherichia coli BL21 (DE3) with a production of 17,267 ± 2037 U/ml.ConclusionsTo our knowledge, these results represent one of the highest fermentation levels reported among current catalase-producing strains. This FZSF01 catalase may be suitable for several industrial applications that comprise exposure to alkaline conditions and under a wide range of temperatures.  相似文献   

20.
BackgroundAt present, species known as camote de cerro (Dioscorea spp.) are found only in the wilderness in Mexico, but their populations are extremely depleted because they are indiscriminately collected, it is urgent to evaluate the conservation status of these plants in order to design conservation genetics programs. In this study, genetic diversity parameters along with cluster analysis based on Jaccard's coefficient were estimated with the objective to assess the efficiency of Random Amplified Polymorphic DNA (RAPD), Inter Simple Sequence Repeat (ISSR), Amplified Fragment Length Polymorphism (AFLP) and Inverse Sequence Tagged Repeat (ISTR) molecular DNA markers in the Dioscorea genus.ResultsThe polymorphic information contents were quite similar for all markers (≈ 0.48). Genetic variation of Dioscorea spp., in terms of average heterozygosity was lower with ISTR (0.36), and higher when other markers were used (RAPD = 0.43; ISSR = 0.45 and AFLP = 0.47).ConclusionThis indicates an important level of genetic differences despite the fact that the plant is asexually propagated. Based on the diversity statistics, any marker tested in present work can be recommended for use in large-scale genetic studies of populations. However, the low correlations among different molecular marker systems show the importance of the complementarity of the information that is generated by different markers for genetic studies involving estimation of polymorphism and relationships.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号