Polyurethane Foam Immobilization of Candida tropicalis for Xylitol Production / 微生物学通报

Immobilization conditions of Candida tropicalis to be absorbed in polyurethane foam carrier materials were studied on the xylitol production from corn hemicellulosic hydrolysate. Optimum batch-fermentation conditions were as follows: inoculum amount, 7% (volume ratio); polyurethane foam quantity, 1.0 g/100 mL; 30?C; initial pH, 6.0. Shaking speed was divided into two-phase to accommodate the dissolved oxygen, with 200 r/min at 0~24 h and 150 r/min at 24 h~46 h. The immobilized cells on polyurethane foam carrier have high density and good resistance to inhibitors in the hydrolysates. Average xylitol yield and volumetric productivity of polyurethane foam immobilized fermentation were much higher than the fermentation without immobilization. Corn cob hydrolysates can be directly biotransformed to xylitol without decoloration or ion-exchange treatment. This process can effectively reduce production costs, and it shows broad prospects of applications. Average xylitol yield was 67.6% and xylitol volumetric productivity was 1.92 g/(L?h).

Cloning and secretion expression of hepcidin in Pichia pastoris / 生物工程学报

Hepcidin is a liver-expressed, small cysteine rich peptide that acts as a regulator of systemic iron homeostasis. In this work, according to the partiality codon of Pichia pastoris, a DNA fragment containing the coding sequence of hepcidin was designed and synthesized, especially a Kex2 signal cleavage site was fused in 5' end of the antibacterial peptide genes. Then the modified hepcidin gene was inserted into the Pichia pastoris expression vector plasmid pPICZalpha-A. After electroporation of the resulting vector, pPICZalpha-A-Hepc, into the yeast host strain GS115, transformants with high copy inserts were selected by 1500 mg/L Zeocin selection. Under the control of the promoter AOX1 (alcohol oxidase 1), recombinant hepcidin secreted from P. pastoris had a molecular weight of 2.7kD. After optimization of the flask-shaking culture fermentation, the yield of hepcidin reached 100 mg/L in the clarified broth. Through antibacterial assay, the recombinant hepcidin displayed obvious antibacterial activity against Bacillus subtilis. But it could not distinctly inhibit the growth of E. coli BL21 (DE3).

Properties and advance of hepcidin / 生物工程学报

Hepcidin is a small cystein-rich cationic peptide produced mainly by the liver. It was initially isolated from human plasma and exhibited antimicrobial activity. Recently, several lines of evidence have suggested that hepcidin is a key regulator of iron metabolism at the whole body level and is relative to inflammation, infection, hypoxia and anemia. Hepcidin, is implicated in duodenal iron absorption and iron mobilization from reticuloendothelial macrophages. The major mechanism of hepcidin function seems to be the regulation of transmembrane iron transport. As both iron deficiency and iron excess are associated with cellular dysfunction, so hepcidin or hepcidin-related therapeutics could find a place in the treatment of various diseases such as hemochromatosis and anemia of chronic disease. To elucidate biological function of hepcidin further and use it for other research, it is necessary to produce enough hepcidin through DNA recombinant technique. As a highly successful system for the production of a variety of heterologous proteins, the methylotrophic Pichia pastoris system has the probability for a high level production of hepcidin. The subject of this paper is to summarize the regulation of hepcidin gene expression and the understanding of functions of hepcidin. At last, giving a prospect of production hepcidin by gene engineer.

The Study on Gene Engineering Strains Producing Lycopene / 中国生物工程杂志

Lycopene—a kind of important active compound of caroteinoids, is greatly beneficial to human health with its diverse biological functions. With the elucidation of lycopene biosynthetic pathway and cloning genes of relative enzymes from microorganisms, it is possible to regulate lycopene biosynthesis via genetic engineering. The biosynthesis pathways of lycopene and gene cloning of lycopene biosynthetic enzymes in microorganisms were reviewed, and gene engineering strains documented in previous works including: E.coli and yeast constructed by genetic recombination, mold strains enhanced the ability of producing lycopene by gene manipulation were summarized. At last, compared with the present methods, the problems existed in the process of construction were pointed out.

Effect of iontophoresis on skin permeation of defibrase / 药学学报

<p><b>AIM</b>To investigate the effect of iontophoresis on skin permeation of defibrase.</p><p><b>METHODS</b>Iontophoresis was carried out in side-by-side chambers, excised rat skin membrane (RSM) or human epidermis membrane (HEM). The effects of electrode polarity, permeation medium pH and ionic strength were evaluated.</p><p><b>RESULTS</b>Permeation of defibrase caused by anodal iontophoresis was more effective [the apparent permeability coefficient was (1.2 +/- 0.4) x 10(-4) cm x h(-1)] than that of cathodal iontophoresis [(4.3 +/- 1.4) x 10(-5) cm x h(-1)]. The amount of permeated defibrase caused by anodal iontophoresis in pH 7.4 medium was (25 +/- 5) x 10(-14) mol x cm(-2), which was higher than that of in pH 6. 4 permeation medium [(15 +/- 4) x 10(-14) mol x cm(-2)].</p><p><b>CONCLUSION</b>Iontophoresis could enhance skin permeation of defibrase. Electroosmotic flow effect played an important role.</p>

Trehalose Production by Permeabilized Cells / 微生物学通报

A permeabilization method of Micrococcus cells has been established. The obtained penneabilized cells could be used for several batches and in the mean time the intracellular enzymes still keep high activity. This method will undoubtedly increase the productivity of the cells and cut down the cost; therefore, it will be a promising way in the treha-lose industrialization. The experiment shows: after being treated with 5% (v/v) methylbenzene for 40min, the cells in suspension were converted into permeabilized cells, then the latter acted on 10% liquefied starch to produce trehaloae, the conversion ratio could reach 70%. The penneabilized cells could be used at least for 6 batchs (12h per batch) and the intracellular enzyme activity kept steady.

HE EFFECT OF MYCELIAL MORPHOLOGY ON LYCOPENE FERMENTATON / 微生物学通报

Mycelial morphology are exploited a great influnence to the metabolites of fungi. The effect of the mycelial morphology on producing lycopene by Blakeslea tripora was investigated. The results indicated that pellets has little role on fermentation when adding kerosene and triton-x100, However, The content of lycopene in the medium reached to 98.6mg/L by adding Ig/L span-20, forming dispersed mycelia, which is 3 times of the control experiments.

THE EFFECT OF IMMOBILIZATION PROCESS TO THE ACTIVITY OF MTHASE AND MTSASE / 微生物学通报

Amylum can be transformed into trehalose on the action of the MTSase and MTHase, however, the percentage of transformation is low. The research on the enzyme immobilization through four kinds of immobilization carrier is described in this paper. The result shows that the carriers, which are put into with enzyme liquid and crossbonded with chi-tosan and glutaraldehyde at first, can adsorb many enzymes independent from this process of trehalose synthesizing, consequently, the enzyme activity is increased sharply. By comparing with the influence of the immobilizing process and some factors in the reaction conditions, such optimize condition can be reached: the time for carrier crossbonding with glutaraldehyde is 18hours , the time with enzyme is another 18hours , and the time of reaction with amylum (10%) is 9hours.The result of the content of trehalose can reach 27.22g/L and the percentage of transformation can reach 54.43% , which previously is 2.67g/L and 5.33% respectively before dealt with by carriers.

PURIFICATION OF SOYA OLIGOSACCHARIDE BY FERMENTATION / 微生物学通报

Selection of utilization of carbon source in soya oligosaccharide by three strains of S.cerevisiae was studied.The results showed that S.cerevisiae C could selectively utilize sucrose and the residual rate of stachyose and raffinose could be more than 96%.Using yeast extract as nitrogen source,the sucrose could be used up after 36 hours of culture.Further study showed that the content of sucrose in soya oligosaccharide powder was less than 1.3% after fermentation of waste water of soy whey and downstream processing.

The Influence of Lonone and Ergosterol on the Growth and the Yield of CoQ_(10) in Yeast / 微生物学通报

The influence of ?-ionone and ergosterol on the growth and the yield of CoQ_ 10 in yeast was investigated. The results indicated that ?-ionone had the stimulative effect on the biosynthesis of CoQ_ 10 in yeast, and 28.3% increase of the CoQ_ 10 content in the cell was observed when the concentration of ?-ionone in the medium was 0.208?10~ -3 mol/L. Little ergosterol also had the same effect with ?-ionone, while 31.3% increase of the CoQ_ 10 content in the cell was observed when the concentration of ergosterol in the medium was 0.15?10~ -4 mol/L. However, the biosynthesis of CoQ_ 10 was inhibited when the concentration of ergosterol was 0.60?10~ -4 mol/L. Addition of ?-ionone and ergosterol to the medium resulted in 36.1% increase over the control. The results showed that the cell could effectively accumulate more CoQ_ 10 with the addition of ?-ionone and ergosterol to the medium.

Isolation,Purification and Identification of Recombinant Human Hepcidin / 微生物学通报

Method of isolation and purification of recombinant hepcidin was described, and the bioactivity of the protein was assayed in this paper.The oxidation of his-hepcidin was carried out in the cysteine-cystine system, and the multimers were removed through gel filtration under denaturation condition.Then the protein was refolded by continuous dilution and digested by enterokinase.The total yield of his-hepcidin before enterokinase cleavage is 50%, and the purity is above 95%.Through agar diffusion assay, the recombinant hepcidin displayed obvious antibacterial activity against B.subtilis.The LC-ESI-MS analysis of recombinant hepcidin showed that the measured molecular weight accorded with the calculated molecular weight, and the CD spectrum indicated that the secondary structure of recombinant hepcidin is similar with native hepcidin.

Enhancement of Lycopene Production by Blakeslea trispora Using Oxygen-vectors and Surface Active Agents / 微生物学通报

Addition of oxygen-vectors(n-dodecane,n-hexane,hydrogen peroxide) to fermentation medium was recognized as a method of enhancing oxygen transfer and promoting lycopene yield by Blakeslea trispora fermentation.Higher lycopene production was observed in shake flask containing 1%(v/v) n-hexane,n-dodecane and 150 L/100mL hydrogen peroxide as compared to shake flasks without oxygen-vectors.The result of assays indicated that when oxygen-vectors (n-dodecane,n-hexane,1%,v/v) and hydrogen peroxide(50 L/100mL) were added to the 0-day and 1-day old culture of Blakeslea trispora the production of lycopene were 25.32%,72.84% and 40.35% higher than those without oxygen-vectors addition respectively.The production of lycopene increased 114.83% when n-dodecane and surface active agents were used at the same time.