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1.
BackgroundRhodotorula glutinis is capable of synthesizing numerous valuable metabolites with extensive potential industrial usage. This paper reports the effect of initial culture medium pH on growth and protein, lipid, and carotenoid biosynthesis by R. glutinis.ResultsThe highest biomass yield was obtained in media with pH 4.0–7.0, and the value after 72 h was 17.2–19.4 gd.w./L. An initial pH of the medium in the range of 4.0–7.0 has no significant effect on the protein (38.5–41.3 g/100 gd.w.), lipid (10.2–12.7 g/100 gd.w.), or carotenoid (191.7–202.9 μg/gd.w.) content in the biomass or on the profile of synthesized fatty acids and carotenoids. The whole pool of fatty acids was dominated by oleic (48.1–53.4%), linoleic (21.4–25.1%), and palmitic acids (13.0–15.8%). In these conditions, the yeast mainly synthesized torulene (43.5–47.7%) and β-carotene (34.7–38.6%), whereas the contribution of torularhodin was only 12.1–16.8%. Cultivation in medium with initial pH 3.0 resulted in a reduction in growth (13.0 gd.w./L) and total carotenoid (115.8 μg/gd.w.), linoleic acid (11.5%), and torularhodin (4.5%) biosynthesis.ConclusionThe different values of initial pH of the culture medium with glycerol and deproteinized potato wastewater had a significant effect on the growth and protein, lipid, and carotenoid biosynthesis by R. glutinis.  相似文献   

2.
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   

3.
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   

4.
BackgroundFermentation process development has been very important for efficient ethanol production. Improvement of ethanol production efficiency from sweet sorghum juice (SSJ) under normal gravity (NG, 160 g/L of sugar), high gravity (HG, 200 and 240 g/L of sugar) and very high gravity (VHG, 280 and 320 g/L of sugar) conditions by nutrient supplementation and alternative feeding regimes (batch and fed-batch systems) was investigated using a highly ethanol-tolerant strain, Saccharomyces cerevisiae NP01.ResultsIn the batch fermentations without yeast extract, HG fermentation at 200 g/L of sugar showed the highest ethanol concentration (PE, 90.0 g/L) and ethanol productivity (QE, 1.25 g/L·h). With yeast extract supplementation (9 g/L), the ethanol production efficiency increased at all sugar concentrations. The highest PE (112.5 g/L) and QE (1.56 g/L·h) were observed with the VHG fermentation at 280 g/L of sugar. In the fed-batch fermentations, two feeding regimes, i.e., stepwise and continuous feedings, were studied at sugar concentrations of 280 g/L. Continuous feeding gave better results with the highest PE and QE of 112.9 g/L and 2.35 g/L·h, respectively, at a feeding time of 9 h and feeding rate of 40 g sugar/h.ConclusionsIn the batch fermentation, nitrogen supplementation resulted in 4 to 32 g/L increases in ethanol production, depending on the initial sugar level in the SSJ. Under the VHG condition, with sufficient nitrogen, the fed-batch fermentation with continuous feeding resulted in a similar PE and increased QP by 51% compared to those in the batch fermentation.  相似文献   

5.
BackgroundCurrently, microbial fermentation method has become the research hotspot for acetoin production. In our previous work, an acetoin-producing strain, Bacillus subtilis SF4-3, was isolated from Japanese traditional fermented food natto. However, its conversion of glucose to acetoin was relatively low. In order to achieve a high-efficient accumulation of acetoin in B. subtilis SF4-3, main medium components and fermentation conditions were evaluated in this work.ResultsThe by-products analysis showed that there existed reversible transformation between acetoin and 2,3-butanediol that was strictly responsible for acetoin production in B. subtilis SF4-3. The carbon sources, nitrogen sources and agitation speed were determined to play crucial role in the acetoin production. The optimal media (glucose·H2O 150 g/L, yeast extract 10 g/L, corn steep dry 5 g/L, urea 2 g/L, K2HPO4 0.5 g/L, MgSO4 0.5 g/L) were obtained. Furthermore, the low agitation speed of 300 r/min was found to be beneficial to the reversible transformation of 2,3-butanediol for acetoin production in B. subtilis SF4-3. Eventually, 48.9 g/L of acetoin and 5.5 g/L of 2,3-butanediol were obtained in a 5-L fermenter, and the specific production of acetoin was 39.12% (g/g), which accounted for 79.90% of the theoretical conversion.ConclusionsThe results indicated acetoin production of B. subtilis SF4-3 was closely related to the medium components and dissolved oxygen concentrations. It also provided a method for acetoin production via the reversible transformation of acetoin and 2,3-butanediol.  相似文献   

6.
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   

7.
BackgroundChlorophytum borivilianum is a rare medicinal plant originally distributed throughout the forest of India. The tubers of C. borivilianum are used as an aphrodisiac and impotence supplement. The propagation of C. borivilianum is possible through seeds and tubers, but conventional methods may take several months. Hence in vitro technique of shoot regeneration could be an efficient alternative means of propagating the species. Latest study reported microtuberization of C. borivilianum but there is no sufficient study on a rapid method for shoot multiplication and elongation.ResultsYoung shoot buds of C. borivilianum were cultured on MS medium containing 6-benzylaminopurine (BAP) and Kinetin (Kn), both at 0, 8.88, 17.8 and 26.6 μM, either individually or in combinations. Proliferated shoots were subcultured on fresh medium of the same constituents on week 3 of culture for further shoot multiplication and elongation. BAP alone (8.88–26.6 μM) was significantly effective on shoot multiplication, while Kn alone (8.88–26.6 μM) was significantly effective on shoot elongation compared to the control containing MS basal medium without any plant growth regulator. However, combination of both cytokinins stimulated an interaction producing higher shoot number and shoot length compared to their individual application.ConclusionsThe most suitable combination was 8.88 μM BAP + 8.88 μM Kn, reaching a mean shoot number of 10.83 and shoot length of 6.85 cm.  相似文献   

8.
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   

9.
BackgroundLipases are used in detergent industries to minimise the use of phosphate-based chemicals in detergent formulations. The use of lipase in household laundry reduces environmental pollution and enhances the ability of detergent to remove tough oil or grease stains.ResultsA lipase-producing indigenous Bacillus subtilis strain [accession no. KT985358] was isolated from the foothills of Trikuta mountain in Jammu and Kashmir, India. The lipase (BSK-L) produced by this strain expressed alkali and thermotolerance. Lipase has an optimal activity at pH 8.0 and temperature 37°C, whereas it is stable at pH 6.0–9.0 and showed active lipolytic activity at temperatures 30 to 60°C. Furthermore, lipase activity was found to be stimulated in the presence of the metal ions Mn2 +, K+, Zn2 +, Fe2 + and Ca2 +. This lipase was resistant to surfactants, oxidising agents and commercial detergents, suggesting it as a potential candidate for detergent formulation. BSK-L displayed noticeable capability to remove oil stains when used in different washing solutions containing buffer, lipase and commercial detergent. The maximum olive oil removal percentage obtained was 68% when the optimum detergent concentration (Fena) was 0.3%. The oil removal percentage from olive oil-soiled cotton fabric increased with 40 U/mL of lipase.ConclusionsThis BSK-L enzyme has the potential for removing oil stains by developing a pre-soaked solution for detergent formulation and was compatible with surfactants, oxidising agents and commercial detergents.  相似文献   

10.
BackgroundIn the industrial biotechnology, ligninolytic enzymes are produced by single fungal strains. Experimental evidence suggests that co-culture of ligninolytic fungi and filamentous microfungi results in an increase laccase activity. In this topic, only the ascomycete Trichoderma spp. has been studied broadly. However, fungal ligninolytic-filamentous microfungi biodiversity interaction in nature is abundant and poorly studied. The enhancement of laccase and manganese peroxidase (MnP) activities of Trametes maxima as a function of time inoculation of Paecilomyces carneus and under several culture conditions using Plackett–Burman experimental design (PBED) were investigated.ResultsThe highest increases of laccase (12,382.5 U/mg protein) and MnP (564.1 U/mg protein) activities were seen in co-cultures I3 and I5, respectively, both at 10 d after inoculation. This level of activity was significantly different from the enzyme activity in non-inoculated T. maxima (4881.0 U/mg protein and 291.8 U/mg protein for laccase and MnP, respectively). PBED results showed that laccase was increased (P < 0.05) by high levels of glucose, (NH4)2SO4 and MnSO4 and low levels of KH2PO4, FeSO4 and inoculum (P < 0.05). In addition, MnP activity was increased (P < 0.05) by high yeast extract, MgSO4, CaCl2 and MnSO4 concentrations.ConclusionsInteraction between indigenous fungi: T. maxima–P. carneus improves laccase and MnP activities. The inoculation time of P. carneus on T. maxima plays an important role in the laccase and MnP enhancement. The nutritional requirements for enzyme improvement in a co-culture system are different from those required for a monoculture system.  相似文献   

11.
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   

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.
BackgroundAspartic proteases are a subfamily of endopeptidases that are useful in a variety of applications, especially in the food processing industry. Here we describe a novel aspartic protease that was purified from Peptidase R, a commercial protease preparation derived from Rhizopus oryzae.ResultsAn aspartic protease sourced from Peptidase R was purified to homogeneity by anion exchange chromatography followed by polishing with a hydrophobic interaction chromatography column, resulting in a 3.4-fold increase in specific activity (57.5 × 103 U/mg) and 58.8% recovery. The estimated molecular weight of the purified enzyme was 39 kDa. The N-terminal sequence of the purified protein exhibited 63–75% identity to rhizopuspepsins from various Rhizopus species. The enzyme exhibited maximal activity at 75°C in glycine–HCl buffer, pH 3.4 with casein as the substrate. The protease was stable at 35°C for 60 min and had an observed half-life of approximately 30 min at 45°C. Enzyme activity was not significantly inhibited by chelation with ethylenediamine tetraacetic acid (EDTA), and the addition of metal ions to EDTA-treated protease did not significantly change enzyme activity, indicating that proteolysis is not metal ion-dependent. The purified enzyme was completely inactivated by the aspartic protease inhibitor Pepstatin A.ConclusionBased on the observed enzyme activity, inhibition profile with Pepstatin A, and sequence similarity to other rhizopuspepsins, we have classified this enzyme as an aspartic protease.  相似文献   

14.
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   

15.
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   

16.
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   

17.
BackgroundFatty acid synthase (FAS) is a key enzyme of de novo lipogenesis (DNL), which has been cloned from several species: Gallus gallus, Mus musculus, Homo sapiens, but not from Anas platyrhynchos. The current study was conducted to obtain the full-length coding sequence of Peking duck FAS and investigate its expression during adipocyte differentiation.ResultsWe have isolated a 7654 bp fragment from Peking duck adipocytes that corresponds to the FAS gene. The cloned fragment contains an open reading frame of 7545 bp, encodes a 2515 amino acid protein, and displays high nucleotide and amino acid homology to avian FAS orthologs. Twelve hour treatment of oleic acid significantly up-regulated the expression of FAS in duck preadipocytes (P < 0.05). However, 1000 μM treatment of oleic acid exhibited lipotoxic effect on cell viability (P < 0.05). In addition, during the first 24 h of duck adipocyte differentiation FAS was induced; however, after 24 h its expression level declined (P < 0.05).ConclusionWe have successfully cloned and characterized Peking duck FAS. FAS was induced during adipocyte differentiation and by oleic acid treatment. These findings suggest that Peking duck FAS plays a similar role to mammalian FAS during adipocyte differentiation.  相似文献   

18.
BackgroundEndoglucanase plays a major role in initiating cellulose hydrolysis. Various wild-type strains were searched to produce this enzyme, but mostly low extracellular enzyme activities were obtained. To improve extracellular enzyme production for potential industrial applications, the endoglucanase gene of Bacillus subtilis M015, isolated from Thai higher termite, was expressed in a periplasmic-leaky Escherichia coli. Then, the crude recombinant endoglucanase (EglS) along with a commercial cellulase (Cel) was used for hydrolyzing celluloses and microbial hydrolysis using whole bacterial cells.ResultsE. coli Glu5 expressing endoglucanase at high levels was successfully constructed. It produced EglS (55 kDa) with extracellular activity of 18.56 U/mg total protein at optimal hydrolytic conditions (pH 4.8 and 50°C). EglS was highly stable (over 80% activity retained) at 40–50°C after 100 h. The addition of EglS significantly improved the initial sugar production rates of Cel on the hydrolysis of carboxymethyl cellulose (CMC), microcrystalline cellulose, and corncob about 5.2-, 1.7-, and 4.0-folds, respectively, compared to those with Cel alone. E. coli Glu5 could secrete EglS with high activity in the presence of glucose (1% w/v) and Tween 80 (5% w/v) with low glucose consumption. Microbial hydrolysis of CMC using E. coli Glu5 yielded 26 mg reducing sugar/g CMC at pH 7.0 and 37°C after 48 h.ConclusionsThe recombinant endoglucanase activity improved by 17 times compared with that of the native strain and could greatly enhance the enzymatic hydrolysis of all studied celluloses when combined with a commercial cellulase.  相似文献   

19.
BackgroundLysozyme plays a crucial role in innate immunity with its well-recognized bacteriolytic activity. In this study, the influence of expression parameters (inoculation volume, culture volume, growth time, induction temperature and time, initial pH and methanol concentration) on human lysozyme (HLZ) production in recombinant P. pastoris SMD1168 was investigated through Plackett–Burman (PB) design and response surface methodology (RSM).ResultsIt was revealed that induction temperature, induction time and culture volume had significant influence (P < 0.01) on HLZ expression level, which were elected for further optimization with three-dimensional response surface designs for enhanced HLZ production. The highest lysozyme activity reached 3301 U/mL under optimized conditions (at 23.5°C for 90 h with culture volume of 48 mL) in shake flask, which increased 2.2 fold compared with that achieved with the standard protocol (Invitrogen). When high-cell-density fermentation of the recombinant Pichia pastoris was performed in a 15 L fermenter under optimized conditions, the extracellular lysozyme activity reached 47,680 U/mL. SDS-PAGE analysis of the product demonstrated that HLZ was produced as a single major protein with a molecular weight of approximately 14.7 kDa, consistent with its expected size.ConclusionsThe results indicated that the optimized culture conditions using PB design and RSM significantly enhanced the expression level of HLZ, and the Pichia expression system for HLZ production was successful and industrially promising.  相似文献   

20.
BackgroundJuvenile Yoshitomi tilapia is often infected by pathogens and results in low-level survival rate. Bacillus subtilis, as a probiotic, may have beneficial effects on Y. tilapia with compound 1-deoxynojirimycin (DNJ), which has antibacterial activities. The effects of dietary probiotic supplementation on Y. tilapias were evaluated.ResultsJuvenile Y. tilapia was fed with B. subtilis for 56 d. Y. tilapia was infected by Aeromonas hydrophila and survival rate was compared. Dietary B. subtilis increased weight gain rate, specific growth, food conversion ratios and food intake rate of Y. tilapia. The diet improved the cumulative survival rate (CSR) of juvenile Y. tilapia when the concentration of B. subtilis was more than 2.05 × 1010 cfu/kg and CSR reached a maximum rate when the concentration of bacillus was 4.23 × 1010 (P < 0.05). Meanwhile, B. subtilis improved total antioxidant capacity (TAC), spleen index, the activities of serum lysozyme, alkaline phosphatase (ALP), superoxide dismutase (SOD) and catalase (CAT) (P < 0.05). In contrast, B. subtilis reduced serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), malondialdehyde (MDA) and C3 complement (P < 0.05). DNJ was isolated from secondary metabolisms and proved to increase the levels of SOD, CAT and reduce the levels of AST, ALT and MDA at cell levels. After A. hydrophila infection, DNJ prevented the reduction in survival rate of Y. tilapia (P < 0.05).Conclusions1-Deoxynojirimycin from Bacillus subtilis can be used to improve the growth performance of juvenile Y. tilapia by affecting its antioxidant and antibacterial activities.  相似文献   

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