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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.104, #2)
β-d-Galactopyranosyl azide by Beatrice Rob; Reuben E. Huber (pp. 97-104).
A simple one-step synthesis of β-d-galactopyranosyl azide from 0-nitrophenyl-β-d-galactopyranoside and azide catalyzed by E461G-β-galactosidase is described. The synthesis is quantitative in the presence of excess azide and only the β anomer is produced. The product was purified (71% yield) from the other reaction components by extraction with ethyl acetate, silica gel chromatography, and crystallization. The purity was verified by GLC, TLC, and NMR. Thus, E461G-β-galactosidase is able to specifically and quantitatively from β-d-galactopyranosyl-azide. The purified β-d-galactopyranosylazide inhibited the growth of Escherichia coli that express β-galactosidase but not of E. coli that do not. Growth is stopped because β-galactosidase catalyzes the hydrolysis of the β-galactopyranosyl-azide, and the azide that is produced inhibits cell growth. This selective inhibition of growth has potential application in molecular biology screening.
Keywords: β-Galactosidase; screening; molecular biology; synthesis
Lipase-catalyzed interesterification of soybean oil with an ω-3 polyunsaturated fatty acid concentrate prepared from sardine oil by Masamichi Akimoto; Maki Izawa; Kazumi Hoshino; Ken-Ichi Abe; Hiromi Takahashi (pp. 105-118).
Toreduce the content of limoleoyl moiety in soybean oil, soybean oil that contains 53.0% linoleoyl moiety as molar acyl moiety composition was interesterified with an ω-3 polyunsaturated fatty acid (PUFA) concentrate (240 mol% elcosapentaenoic acid [EPA], 40.4 mol% docosahexaenoic acid [DHA]) prepared from sardine oil, using an immobilized sn-1,3-specific lipase from Rhizomucor michei (Lipozyme IM). The reaction was carried out in a batch reactor at 37°C under the following conditions: 500 μmol of soybean oil, molar ratio of ω-3 PUFA concentrate to soybean oil=1.0–6.0, 5.0 mL of heptane, and 30 batch interesterification units of enzyme. After the reaction time of 72h, modified soybean oil, which contains 34.9% linoleoyl, 10.1% eicosapentaenoyl, and 14.2% docosahexaenoyl moieties, was produced at the molar reactant ratio of 6.0. In this oil, the total ω-3 acyl moiety composition reached 34.1%; the molar ratio of ω-3 to ω-6 acyl moieties was enhanced by five times compared with soybean oil. Compared with palmitic acid, DHA was kinetically six times less reactive, although the EPA was by 16% more reactive.
Keywords: Interesterification; acidolysis; kinetics; soybean oil; eicosapentaenoic acid; docosa hexaenoic acid; Rhizomucor michei ; lipase; Lipozyme IM; sardine oil
Biosorption of metal ions with Penicillium chrysogenum by Tianwei Tan; Peng Cheng (pp. 119-128).
Biosorption of metal ions with Penicillium chrysogenum mycelium is described in this article. Alkaline pretreatment was used to remove proteins and nucleic acids from cells, and this treatment increased the adsorption capacities, for Cr3+ from 18.6 mg g−1 to 27.2 mg g−1, for Ni2+ from 13.2 mg g−1 to 19.2 mg g−1, for Zn2+ from 6.8 mg g−1 to 24.5 mg g−1. The adsorption of metal ions was strongly pH dependent. The mycelium could beused for large-scale removal of Cr3+ from tannery wastewater. The results show that this inexpensive mycelium adsorbent has potential in industry because of its high adsorption capacity. The main chelating sites are amino groups (−NH2) of chitosan in the mycelium. A new model is established, which describes the relation of adsorption of metal ions on pH according to amino group chelating with metal ions and H+. The relative errors of simulation for Cu2+, Ni2+, Zn2+, and Cr3+ are 4.66%, 5.45%, 11.55%, and 1.69%, respectively.
Keywords: Penicillium chrysogenum ; mycelium; adsorption
Improvements in lipase production and recovery from Acinetobacter radioresistens in presence of polypropylene powders filled with carbon sources by In-Liang Liu; Shau-Wei Tsai (pp. 129-140).
Polypropylene powders as the adsorbent for organic solution containing n-hexadecane and olive oil were employed as the carbon source for producing an alkaline lipase from Acinetobacter radioresistens. The best volumetric ratio of n-hexadecane to olive oil around 5 for lipase production was determined from shake-flask and fermentation cultivations. The existence of a maximum time course lipase activity of the aqueous phase was attributed to the compensation effects of olive oil on cell growth and lipase production, repression of lipase synthesis by oleic acid, and lipase adsorption on the supports. A linear relationship between the average cell growth rate in the exponential phase and the ratio of surface areas of the supports was found. The benefits of using the present fermentation process include less foaming and emulsion of the broth, less organic phase used, higher lipase production, and easy recovery of the lipase in the centrifugation step.
Keywords: Alkaline lipase fermentation; polypropylene powders; Acinetobacter radioresistens
Corn-milling pretreatment with anhydrous ammonia by Frank Taylor; James C. Craig Jr.; M. J. Kurantz; Vijay Singh (pp. 141-148).
Exposure to anhydrous ammonia has been suggested as a pretreatment for corn milling. Batches of corn were exposed to ammonia under controlled conditions. The amounts of ammonia absorbed and reacted with the corn were measured. The amounts were not more than are needed as nutritional supplement for yeast fermentation to ethanol. Loosening of the hull was observed qualitatively, and subsequent shearing in a disk mill followed by steeping for 2, 4, 6, or 8h showed that germ could be recovered at higher yield and after a shorter steeping time compared to untreated control batches. Quality of oil was not affected by treatment with ammonia.
Keywords: Corn; ammonia; pretreatment; milling; steeping; ethanol; fermentation
Alkaloid production by callous tissue cultures of Cereus peruvianus (Cactaceae) by Arildo José Braz de Oliveira; Maria de Fátima Pires da Silva Machado (pp. 149-155).
The morphologically undifferentiated cells of nonregenerant callous tissue of Cereus peruvianus cultured in the original medium and in medium supplemented with tyrosine were used as an alkaloid source. Comparison of alkaloid production by C. peruvianus plants and by callous tissues indicated that alkaloid levels were almost twice as high in callous tissues as in shoots of C. peruvianus plants. The ratio of alkaloid concentration between mature plant and morphologically und ifferentiated cells of callous tissue was 1∶1.7. A relationship between culture medium containing tyrosine and alkaloid production was also observed in the callous tissues of C. peruvianus. Since increased alkaloid production may be induced by additional factors such as tyrosine, increasing levels of tyrosine or other conditions of the culture medium may be considered factors for inducing higher alkaloid production by C. peruvianus callous tissues.
Keywords: Alkaloids; cactus; callous tissue culture; columnar cactus; mandacara ; tyrosine precursor