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The purpose of the current study was to construct a β-cyclodextrin drug carrier for rubropunctatin to improve its water solubility and light stability for future cytotoxicity studies. The inclusion complexation behavior of rubropunctatin with β-cyclodextrin was investigated using FESEM, FT-IR and XRD. A molecular docking study was performed to elucidate the most probable inclusion structure. The inclusion complex could be completely dispersed in water and had a small size of 121.87 ± 2.13 nm (n = 3), a good PDI (0.320 ± 0.017), and an acceptable potential value of −27.7 ± 0.32 mV (n = 3). Furthermore, the stability of the rubropunctatin in water under light irradiation was found to be greatly enhanced after being encapsulated in cyclodextrin, and it exhibited a retention rate of over 70% vs. 10.17%. In addition, the cytotoxicity of the inclusion complex was evaluated by MTT assay and Annexin V-FITC/PI detection using cervical adenocarcinoma HeLa cells. The results showed that the inclusion complex had comparable toxicity compared to rubropunctatin solubilized with 0.4% DMSO. More importantly, the formation of the inclusion complex contributed greatly to the intensification of the bioavailability of rubropunctatin because the use of organic solvent was avoided.

Phycocyanin (PC) is a natural fluorescent protein which is widely used in medical diagnosis, biology, biotechnology, foods, and medicine. However, the disadvantages in traditional purification methods, such as complicated preparation process, low yield, inadequate quantity, and high price, limit its range of application. In this study, we established a rapid purification method suitable for large-scale production to prepare PC from Arthrospira platensis. The membrane separation and two-stage ammonium sulfate precipitation yielded PC with a purity ratio (A620nm/A280nm) of 3.65. This purification method of PC proved to be efficient and cost-effective compared with previously reported methods. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the molecular weight of α and β subunits of PC was 16.6 and 21.2 kDa. The main molecular weight of intact PC determined through high-performance size exclusion chromatography (HPSEC) was around 91 kDa, indicating that the PC from A. platensis existed mainly in the form of (αβ)3 at pH 7.0. The purified PC fluorescent probe was compatible for light-emitting diode (LED)—charge-coupled device (CCD) fluorescence density strip qualitative detection system. A relatively sensitive novel fluorescent test method was developed for the quantitative detection of PC showing a linear response to PC within the range of 0.07–3.64 μM, and with a limit of detection of 0.034 μM. This method could provide expedient quantitative information and showed great potential for rapid detection in environmental and food safety research.

Alzheimer's disease (AD) is an extremely complex disease, characterized by several pathological features including oxidative stress and amyloid-β (Aβ) aggregation. Blockage of Aβ-induced injury has emerged as a potential therapeutic approach for AD. Our previous efforts resulted in the discovery of Monascus pigment rubropunctatin derivative FZU-H with potential neuroprotective effects. This novel lead compound significantly diminishes toxicity induced by Aβ(1-42) in Neuro-2A cells. Our further mechanism investigation revealed that FZU-H inhibited Aβ(1-42)-induced caspase-3 protein activation and the loss of mitochondrial membrane potential. In addition, treatment of FZU-H was proven to attenuate Aβ(1-42)-induced cell redox imbalance and Tau hyperphosphorylation which caused by okadaic acid in Neuro-2A cells. These results indicated that FZU-H shows promising neuroprotective effects for AD.

Impaired endothelial functions are closely associated with many chronic vascular-related diseases. Maslinic acid (MA), a natural pentacyclic triterpene compound, has received more and more attentions in recent years due to a variety of bioactivities. In the present study, we investigated the effect of MA on impaired endothelial functions in human aortic endothelial cells (HAEC) induced by high glucose treatment and discussed its possible mechanism. We showed that MA decreased the ROS level, inhibited the inflammatory cytokines expression, facilitated insulin-mediated IRS-1/PI3K/Akt/eNOS signaling and suppressed the cellular apoptosis ratio induced by high glucose. The molecular docking results showed that MA may regulate multiple targets to improve the endothelial dysfunction in HAECs exposed to high glucose. These results revealed potential application of MA in improving endothelia dysfunction.

The interest focusing on Eriobotrya japonica leaf triterpene acid (ELTA) has increased recently because of its beneficial effects on health. However, there has been a lack of experimental data on its toxicity. The present study therefore was conducted to evaluate its toxicity in ICR mice. The results showed that ELTA produced neither mortality nor toxicity of the main organs in ICR male and female mice in both acute (0.30, 0.65, 1.39, and 3.00 g·kg−1 body weight) and subacute (150, 300, and 600 mg·kg−1 BW) 28-day toxicity studies. Because of lacking apparently adverse effects found in the hematology, clinical biochemistry, and histopathology evaluation, results of the present study together with the beneficial effects make ELTA as a promising dietary supplement and indicated that ELTA administered orally might have a large safety margin for human.

The Monascus pigment, rubropunctatin, was extracted and purified from red mold rice (RMR), and its cytotoxic activities against human cervical carcinoma HeLa cells were studied under the conditions with or without light irradiation. The IC50 value of rubropunctatin against HeLa cells in the dark was 93.71 ± 1.96 μM (24 h), while the cytotoxic activity was enhanced more than 3 times (IC50 = 24.02 ± 2.17 μM) under light irradiation (halogen lamp, 500 W; wavelength, 597-622 nm; and fluence rate, 15 mW cm(-2), for 30 min). However, the IC50 value of rubropunctatin against the immortalized human cervical epithelial H8 cells was more than 300 μM, even under light irradiation, indicating that rubropunctatin has a favorable selectivity index (SI). Treatment of HeLa cells with rubropunctatin in the dark or under light irradiation resulted in a dose-dependent apoptosis, as validated by the increase in the percentage of cells in the sub-G1 phase and phosphatidylserine externalization, and the inductive effect on HeLa cell apoptosis was boosted by the light irradiation. In addition, treatment with rubropunctatin alone or under light irradiation was found to induce apoptosis in HeLa cells via the mitochondrial pathway, including loss of mitochondrial membrane potential, activation of caspase-3, caspase-8, and caspase-9, and increase of the level of intracellular reactive oxygen species (ROS). It was suggested that rubropunctatin could be a promising natural dual anticancer agent for photodynamic therapy and chemotherapy.

Citrinin (CIT)–protein artificial antigen was prepared by conjugating CIT with keyhole limpet hemocyanin by 1,4-butanediol diglycidyl ether. By immunization and fusion, a hybridoma cell line named K2-F3, which stably secreted the monoclonal antibody (McAb) against CIT was obtained. The titer of the CIT- specific McAbs purified by affinity chromatography came to 1:1.38 × 105. The indirect competitive enzyme-linked immunosorbent assay (ELISA) showed that the detection limit of CIT was 0.01 ng/mL, with a good linearity ranging from 0.01 to 1.0 ng/mL. The McAb was highly specific and cross-reactivity rate was less than 0.01%. The data showed that the ELISA developed could accurately determine CIT in the real contaminated red yeast rice samples. The systematic error was low with the coefficient of variation from 2.91 to 8.53% by the ELISA. PRACTICAL APPLICATIONS CIT is a toxic fungal metabolite. It often occurs in naturally contaminated commodities, such as in corn, barley, wheat, apple and some foods. CIT is hepatonephrotoxic and implicated in disease outbreaks in animals and humans. Nowadays, food security problem due to the contamination of CIT has been a growing concern for the government and the public, especially in Asian countries. In this work, a high-specificity McAb against citrinin was obtained. The indirect competitive ELISA based on the obtained McAb exhibited a high sensitivity and precision. The detection limit of CIT was 0.01 ng/mL. The indirect competitive ELISA developed could determine CIT with a satisfactory precision for the real red yeast rice samples. This work would be helpful for establishing the technology and developing the kit to determine CIT-contaminated samples by ELISA.

Natural 2-phenylethanol (PEA) could be produced on a large scale by way of bioconversion with yeast from l-phenylalanine. In this work the synergistic inhibition effect of the target product PEA and the byproduct ethanol on the bioconversion rate by Saccharomyces cerevisiae R-UV3 was systematically studied and a new kinetic model with an item representing the synergistic effect was proposed. Optimization strategies to repress the inhibition effect of PEA and ethanol were carried out in the mode of fed-batch culture with ISPR. The glucose concentration was regulated at the level of 0.2±0.1g/L by controlling a suitable respiratory quotient on line, which could limit the accumulation of the ethanol lower than 10g/L. In the presence of resin FD0816 with a weight of 10% of the medium, PEA was removed from the broth and the overall PEA concentration and the space-time yield reached 13.7g/L and 0.39g L(-1) h(-1) respectively. The semi-continuous process with ISPR was performed, in which the replacement of the resin was operated repeatedly when the aqueous PEA was over 2.7g/L and bioconversion continued until the bioactivity of the yeast cells declined, consequently achieving a final overall PEA concentration of 32.5g/L and a space-time yield of 0.45g L(-1) h(-1).

In this study, we synthesized a 5-valent pneumococcal conjugate vaccine, which was prepared with the pneumococcal capsular polysaccharides (PCPs) (from Streptococcus pneumoniae 1, 5, 6B, 19F, 23F) and pneumococcal surface protein A (PspA) mediated by 1,4-butanediol diglycidyl ether. The PspA cloned from serotype 19 strain showed good cross-immune response to 1, 5, 6B, and 23F serotypes of Streptococcus pneumonia (S. pneumoniae). Analysis of the maturation process of conjugate polyclonal antibody showed that conjugation with the protein carrier converted the polysaccharide from a weak T cell-independent (TI) antigen to a T cell-dependent (TD) antigen, although antibodies affinity to polysaccharide was not as strong as it to PspA in conjugate. We used an invasive disease mouse model to evaluate the protective efficacy of this conjugate vaccine. Active and passive protection against intraperitoneal challenge with virulent type 6B strain showed that the median survival times for mice immunized with conjugate were significantly longer than that of mice treated with capsular polysaccharides or PspA alone. Our study's results showed that immunization of the 5-valent PspA-capsular polysaccharides conjugate vaccine could afford strong protection to mice against the invasion of 1, 5, 6B, 19F, 23F serotypes S. pneumoniae.

Monascus products have been widely used as food additives and pharmaceuticals. Citrinin is a toxic metabolite produced during the Monascus fermentation. In this work, a quick extraction method with ultrasonic treatment was studied for a complete extraction of citrinin from the fungi cells. Furthermore, the proposed HPLC method has the advantage of the simultaneous determination of Monascus pigments and citrinin without sample pretreatment. Under the optimized HPLC conditions, a baseline resolution of pigments, citrinin and other catabolites was achieved. The detection limit of citrinin reached 0.5 ng mL −1 ( S / N > 3/1) with a fluorescence detector (FD). Eight Monascus pigments were detected, with photodiode array detector (PAD), two of which not yet described. The HPLC fingerprint profile of the eight Monascus pigments and citrinin appears significant for the quality control of the Monascus product.

The kinetic characteristics of the reduction of phenylglyoxylic acid (PGA) to R -(−)-mandelic acid ( R -MA) by the immobilized yeast Saccharomyces cerevisiae FD11b were studied. Compared with the free cells, the immobilized cells showed a higher enantioselectivity for the production of R -MA. However the specific production rate ( q p ) of R -MA with the immobilized cells was lower than that with free cells due to the effects of the external and internal diffusion. When the agitation rate was above 200 rpm, the effect of the external diffusion could be eliminated. The effects of the granule diameter and the cell density immobilized in the granules on the internal diffusion rate of the substrate and the specific production rate of R -MA ( q p ) were investigated. A mathematical model considering the internal diffusion and reduction kinetics was developed to analyze the effect of the internal mass transfer. The experimental data and the simulative results showed that the effect of the internal diffusion on q p could be eliminated when the granule diameter was less than 2.2 mm and the cell density immobilized was lower than 66.7 gdw/L-granules. After excluding the effect of the external and internal diffusion, q p reached 0.355 mmol gdw −1 h −1 , close to that with free cells (0.360 mmol gdw −1 h −1 ) in the same reaction system. The optimal pH for the reduction of PGA with immobilized FD11b was 7.5, and the optimal temperature was 32 °C.

Use of microorganisms for bioleaching processes is commonly limited by low tolerance of extreme culture conditions such as temperature, pH, and pulp density. Adaptation to extreme conditions is the main approach for strain improvement. Traditional methods for breeding strains with tolerance of extreme condition are difficult to apply without genetic tools because of many of such strains are not readily purely cultivated in liquid or agar medium. Here, we developed a method using ultraviolet (UV) irradiation for mutation in a continuous stirred tank reactor (CSTR) for screening to improve the bioleaching performance of a poorly characterized strain of Acidianus brierleyi (A. brierleyi). An improved strain developed with our method exhibited a good tolerance to Cu2+ and a high bioleaching rate of chalcopyrite, which was four-fold better than that of a strain selected by traditional adaptation method. We also designed a countercurrent bioleaching process in stirred tanks in series, and copper recovery in 7–8 days at a 15% chalcopyrite pulp density was more than 90% in a two stage countercurrent reactor.

In the aqueous medium the asymmetric reduction of 2-octanone with Baker's yeast FD-12 was inhibited severely by the substrate and the product at higher concentrations, which resulted in a low yield and a low e.e. value of the object product ( S )-2-octanol. Seven water/organic solvent biphasic systems were assayed in this work. FD-12 showed the best tolerance, catalytic activity and enantioselectivity in the water/ n -dodecane system among the biphasic systems assayed. The metabolic activity retention (MAR) and viability of FD-12 in the n- dodecane containing system were 98% and 91.6%, respectively. The influence of the volume ratio V aq / V org , temperature, pH value and the substrate concentration on the yield of 2-octanol and the e.e.( S ) value was investigated. Under the optimum conditions (in the water/ n -dodecane biphasic system, V aq / V org 20/5, pH 8.0, 32 °C, 2-octanone concentration 500 mM), the final concentration of 2-octanol and the e.e.( S ) value reached 105.60 mM and 89.38%, respectively, after 96 h reduction. The water/ n- dodecane biphasic system with FD-12 was advantageous for the production of ( S )-2-octanol of high final concentration and high e.e.( S ) value.

The kinetics of asymmetric production of R-(–)-mandelic acid (R-MA) from phenylglyoxylic acid (PGA) catalyzed by Saccharomyces cerevisiae sp. strain FD11b was studied by fed-batch cultures. The concentrations of glucose and PGA were controlled respectively with a dual feeding system. When the electron donor glucose was supplied at the rate of 0.0833mmol·gdw−1·h−1, the specific production rate (qp) and the enantiomeric excess of R-MA reached the maximum 0.353mmol·gdw−1·h−1 and 97.1%, respectively. The apparent reduction activity of yeast FD11b was obviously affected by both substrate PGA and product MA. The qp value reached the maximum 0.36—0.38mmol-gdw−1·h−1 when the PGA concentration was controlled between 25 and 35mmol·L−1. The obvious substrate inhibition of bioconversion was observed at the PGA concentrations higher than 40mmol·L−1. The accumulation of product MA also caused a severe feed-back inhibition for its production when the product concentration was above 60mmol·L−1. The kinetic model with the inhibition effect of both substrate and product was simulated by a computer-based least-square arithmatic. The established kinetic model was in good agreement with the experimental data.

Screening from 40 microorganisms belonging to different taxonomical groups ( Saccharomyces cerevisiae , Lactoballius, Streptococcus faecalis and Candida albicans ) was performed to select the strain with high production rate of R-(−)-mandelic acid (R-MA). A sp. strain S. cerevisiae FD11b with high yield and enantiomeric excess (e.e.) and little byproducts was obtained by means of UV-mutation breeding. In the optimal conditions of pH 6.5, 32 °C, anaerobic and glucose supply rate ( F glu ) 0.0833 mmol gdw −1 h −1 , the strain FD11b showed a high specific MA production rate ( q p = 0.35 mmol gdw −1 h −1 ) and enantioselectivity (e.e. = 97.1%). The phenylglyoxylic acid (PGA) concentration showed a remarkable effect on the apparent activity of MA dehydrogenase. The specific production rate ( q p ) reached the maximum at 30–40 mM of PGA concentrations. At higher concentrations of PGA more than 40 mM, the q p decreased obviously in a linear way. However, the e.e. of R-MA kept about 95–96.5%, when the PGA concentration was below 60 mM, even at the concentration of PGA 80 mM, the e.e. was still higher than 90%. A modified Monod type equation based on a hypothesis of substrate inhibition could fit the experimental data well. The estimated maximum specific production rate ( q pm ) and saturation constant ( K s ) were 0.431 mmol gdw −1 h −1 and 5.88 mM, respectively.

The efforts were focused on exploring alternative pneumococcal vaccine strategies, aimed at addressing the shortcomings of existing formulations, without compromising efficacy. Our strategy involved the use of the carrier protein, pneumococcal surface protein A (PspA), conjugated with capsular polysaccharides (CPS), to provide effective and non-serotype-dependent protection. In this study, we generated a stable Escherichia coli construct expressing functional PspA from a capsular serotype 6B strain and confirmed it belonging to family 1, which was conjugated with CPS. The distribution of anti-CPS antibody response was almost completely of IgG2a subclass followed by IgG3 and low level of IgG1 subclass, but that of anti-PspA IgG subclass antibodies was almost equal IgG1 and IgG2a subclasses. Though PspA was less conspicuous on the surface of pneumococci than the capsule, the antibodies induced with CPS-rPspA conjugate possessed more accessibility to the surface of Streptococcus pneumoniae serotype 6B and 19F (the same family 1 PspA). By survival experiment, the result suggested that the level of cross-protection after immunized with the conjugate was more measurable within the same family 1. The CPS-rPspA conjugate not only induced CPS-specific protection but also provided PspA specific cross-protection.

A sensitive and selective Pb(2+) sensor based on GR-5 DNAzyme has been developed by a flow cytometric method.

Structural modification was performed at the C-3 and C-28 positions of ursolic acid (UA). Ten UA derivatives with distinct electrical property were synthesized. They could be divided into two groups according to their charge under physiological conditions: (1) Group I negatively charged and (2) Group II positively charged. The anti-proliferative capability of the derivatives was evaluated against HepG2, AGS, HT-29 and PC-3 cells by the MTT assay. Flow cytometry and Annexin V/PI dual staining assay were carried out to explore the antitumor mechanism. The results showed the cytotoxic capacity of the compounds was: Group I

Ursolic acid (UA) as the leader compound was designed to prepare a series of derivatives (three novel compounds UA-1a , UA-1b and UA-2 ) by modification at the C3 and C28 positions. Their chemical structures were confirmed by IR, 1 H NMR and MS. The cytotoxic activity of the derivatives was evaluated against HepG2, BGC-823 and HT-29 by the MTT assay. The novel derivative UA-1a, [3β-acetoxy-urs-12-en-28-oyl]-1-monoglyceride showed significant anti-growth ability against the assayed cancer cell lines, particularly against BGC-823, while low cytotoxicity to human normal gastric cell line GES-1. Further investigation revealed that UA-1a could induce apoptotic events of the treated BGC-823 cells, such as comet-like DNA bend, sub-G0/G1 phase accumulation and phosphatidylserine externalization. The activity of Caspase-3 was found to be up-regulated, while the expression of Bcl-2 and Survivin were down-regulated in UA-1a treated cells. UA-1a might trigger the death of BGC-823 cells by inducing apoptosis via the mitochondria pathway. UA-1a exerted stronger ability than Taxol to retard tumor growth in nude mice without leaving apparent toxicity to the hosts. The experimental data suggested that UA-1a would have a therapeutic potential in the treatment of gastric cancer.

Context Pregnane X receptor (PXR) is an important transcriptional regulator that plays important roles in the cell metabolism and cell growth by regulating the transcriptional of a sort of metabolizing enzymes. Objective To investigate whether rifampicin effected HepG2 cells growth and the inhibition was due to the G0/G1 phase arrest. Methods PXR-knockdown experiments using RNAi showed that the cell cycle phase arrest mediated by rifampicin based on activation of PXR. The results also indicated that cell phase arrest by rifampicin could protect cells form UVB-induced DNA damage. Retinoid X receptor alpha (RXRα) expression level in cells is another key factor for cell cycle phase arrest mediated by rifampicin. Both over expression and lacking expression of RXRα in cell reduced the cell arrest efficiency mediated by rifampicin. In the study, we found that rifampicin inhibited HepG2 cells growth and demonstrated that the inhibition is due to the G0/G1 phase arrest through flow cytometry analysis. Conclusion The results showed that RXRα promote cell cycle phase transition rate of HepG2. Competitive bind of rifampicin-activated PXR with RXRα is one main reason to arrest cell cycle phase through inhibiting combination of RXRα with other partners. Rifampicin could promote cell growth rate when RXRα expressed more excessively than PXR in cells.

Six pigments were separated from Monascus product, and some derivatives were chemically synthesized. The cytotoxicity of different Monascus pigments to various human cancer cells (SH-SY5Y, HepG2, HT-29, BGC-823, AGS, and MKN45) was evaluated. Rubropunctatin showed the greatest anticancer effect within the tested compounds. The inhibition effect of rubropunctatin was higher than that of taxol on the growth of the human gastric cancer cell SH-SY5Y (P

The Monascus pigment, rubropunctatin, was extracted and purified from red mold rice (RMR) and its cytotoxic activities against human gastric adenocarcinoma BGC-823 cells were studied both in vitro and in vivo. Rubropunctatin inhibited the proliferation of BGC-823 cells with an inhibitory concentration (IC50) of 12.57 μM, while it exhibited no significant toxicity to normal gastric epithelial cell GES-1 at the same concentration. Treatment of BGC-823 cells with rubropunctatin resulted in a dose- and time-dependent apoptosis, as validated by the increase in the percentage of cells in sub-G1 phase and phosphotidylserine externalization. The in vivo experimental data demonstrated that rubropunctatin could offer similar therapeutic benefits in comparison with the same dose of taxol. After five times of intravenous injection, tumor weight in BGC-823-bearing nude mice reduced 23.5% at the dose of 8 mg/kg and 37.7% at the dose of 32 mg/kg, respectively. The expressions of 30 genes related to induction of apoptosis were found up-regulated significantly. The two most expressed genes were tumor necrosis factor (TNF) and DNA-damage inducible transcript 3. TNF was considered as a major mediator of apoptosis induced by rubropunctatin. This is the first report describing the anti-proliferative effect of rubropunctatin and its apoptosis mechanism on BGC-823 cells. Rubropunctatin has potential to be developed as a new natural anti-cancer agent.

In this study, a chemically modified homo zwitterionic polysaccharide (ZPS), sulfated chitosan, was used to examine its effects on murine immune response. The results showed that homoZPS could markedly promote the proliferation of both splenic T/B cells and adhesive cells. In particular, flow cytometry assay demonstrated that the sulfated chitosan could non-specifically activate CD3(+) and CD8(+) T cells proliferation in vitro. The effectiveness of sulfated chitosan as adjuvant was tested using bovine serum albumin (BSA) and diphtheria toxin (DT) as antigens and compared with that of aluminum hydroxide. The levels of specific antibodies to BSA and DT significantly increased after homoZPS vaccination. Both homoZPS and aluminum hydroxide adjuvants could protect mice against the attack of DT from edemas of spleen and tail. The present findings demonstrated the chemically derived homoZPS could be a potential candidate in the development of T-lymphocyte dependent vaccine adjuvants.

The efforts were focused on exploring alternative pneumococcal vaccine strategies, aimed at addressing the shortcomings of existing formulations, without compromising efficacy. We generated a stable Escherichia coli construct expressing functional recombinant PsaA and prepared CPS-rPsaA conjugate. The distribution of anti-CPS antibody response was almost completely of IgG2a subclass followed by IgG3 and low level of IgG1 subclass, which was opposite to the distribution of anti-PsaA IgG subclass antibodies. Though rPsaA was not detectable on the surface of the pneumococcal strain, the CPS-rPsaA conjugate possessed more accessibility to the surface of the strain. Mice immunized with conjugate exhibited rapid bacterial clearance from blood for the first 23h and afterward provided the best protection against challenge with pneumococcal 23F strain.

Vitreoscilla hemoglobin Gene was cloned in Streptomyces aureofaciens through E. coli-Streptomyces shuttle plasmids constructed by both pIJ699-pUC19(vhb) and pIJ702-pBR322(vhb). Under low dissolved oxygen conditions, expression of hemoglobin enhanced CTC yield of engineering strain more about 40%-60% that that of control by improving oxygen transmission in cells. Hemoglobin expression by Promoter of tetracycline resistance gene was more effective for oxygen transmission than that by its native promoter regulated by dissolved oxygen concentrations in environments of locally low concentrations of dissolved oxygen.

Vitreoscilla hemoglobin gene was expressed in S. aureofaciens through promoter of tetracycline resistance gene. Characteristics of S. aureofaciens growth and metabolism were studied in 1 m3 fermenter. In high dissolved oxygen concentrations, expression of hemoglobin gene had little effect on growth and metabolism of S. aureofaciens, and there were no obvious differences between engineering strain and control. The chlortetracycline of engineering strain was 22905 u/mL and of control was 22896 u/mL respectively. Under conditions of low dissolved oxygen, expression of hemoglobin enhanced growth, maintenance of energetic mycelium configuration and chlortetracycline yield of S. aureofaciens: the mycelium concentrations of engineering strain were more about 5%-10% and yield was more 11.4% than control.