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Troyano, Esperanza; de Rafael, Daniel; Martinez‐Castro, Isabel; Olano, Agustin
doi: 10.1002/(SICI)1097-4660(199602)65:2<111::AID-JCTB385>3.0.CO;2-Spmid: N/A
Sepiolite (a hydrated magnesium silicate) was investigated as a catalyst for the isomerization of lactose. Factors such as temperature, concentration and time were studied. The main reaction product was lactulose; small amounts of epilactose, galactose, tagatose and 3‐deoxypentulose were also formed. Product distribution indicated that the reaction routes were isomerization of the disaccharide followed by degradation of lactulose.
Van Dyke, Michele I.; Lee, Hung; Trevors, Jack T.
doi: 10.1002/(SICI)1097-4660(199602)65:2<115::AID-JCTB391>3.0.CO;2-Zpmid: 8672293
A rifampicin‐resistant PCB‐degrading Alcaligenes eutrophus H850 strain was marked with luxAB reporter genes and designated H850Lr. This strain was enumerated in soil by viable plating and counting of light‐emitting colonies. The marked strain was also inoculated into soil and sediment microcosms contaminated with PCBs and treated with rhamnolipid biosurfactants produced by Pseudomonas aeruginosa UG2Lr or inoculated with the P. aeruginosa UG2Lr strain. A. eutrophus H850Lr exhibited similar survival in sandy loam soil in the absence or presence of PCBs over 56 days. Survival of A. eutrophus H850Lr in PCB‐contaminated sediment was less than in sandy soil under the same incubation conditions. Addition of P. aeruginosa UG2 rhamnolipids to soil increased the culturable indigenous heterotrophic population, and numbers of A. eutrophus H850Lr cells. P. aeruginosa UG2Lr cells did not affect survival of A. eutrophus H850, as cell enumerations after 2 months were the same as in microcosms containing only A. eutrophus H850 inoculum. P. aeruginosa UG2Lr survived in soils as demonstrated by the slight decrease in CFU from 1 × 108 to 2 × 106 CFU cm−3 after 2 months. Direct extraction of DNA from soil and purification for use in PCR amplification using primers specific for the bphC gene detected 8 × 102 A. eutrophus H850Lr CFU g−1 soil in PCB‐contaminated soils. Colony lifts of bacteria isolated from microcosms containing PCB‐contaminated soil did not hybridize with LB400 bphC probe. However, enrichment of PCB‐contaminated soil with biphenyl, followed by DNA extraction and probing with bphC gene probe detected indigenous PCB‐degrading bacteria containing a similar gene sequence in PCB‐contaminated sediment. This study demonstrates the usefulness of using the lux reporter system in monitoring bacterial survival in PCB‐contaminated soils and sediments.
doi: 10.1002/(SICI)1097-4660(199602)65:2<123::AID-JCTB400>3.0.CO;2-6pmid: 8672294
Recombinant proteins show several types of heterogeneity and post‐translational modifications which are usually related to their production system. The apparent heterogeneity of recombinant interferon γ receptors and interferon γ receptor–immunoglobulin G fusion proteins expressed in Escherichia coli, baculovirus‐infected insect cells and Chinese hamster ovary cells have been studied. In general, all proteins tested showed some type of heterogeneity which was detectable by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The E. coli‐derived receptor included non‐native conformations involving mispaired or non‐formed disulfides. This type of heterogeneity affected the biological activity of the protein. In addition, the prokaryotic protein had trapped phosphoric acid during downstream processing. The phosphoric acid entrapment did not affect ligand binding capacity. The eukaryotic proteins showed heterogeneity because of the unequal cleavage of the signal peptide and because of differences in glycosylation. The latter types of heterogeneity did not affect activity. Glycosylation‐related heterogeneity was partially derived from the unequal utilization of the potential N‐glycosylation sites and differently affected the apparent molecular masses and migrations of the proteins on polyacrylamide gels. The results may be useful in characterization studies of recombinant proteins.
de Miguel, Sergio R.; Caballero Martinez, Alfonso; Castro, Alberto A.; Scelza, Osvaldo A.
doi: 10.1002/(SICI)1097-4660(199602)65:2<131::AID-JCTB404>3.0.CO;2-Upmid: N/A
The effect of lithium addition to γ‐Al2O3 on the acidity and on the catalytic behaviour in the isopropanol dehydration reaction is studied. Results show that there is an important blocking or poisoning effect of lithium on the Lewis Al3+ sites of the alumina surface; these sites play an important role in the isopropanol dehydration reaction to di‐isopropylether and propylene. The di‐isopropylether formation is drastically reduced by lithium addition, while the propylene formation can be maintained, even at a high lithium content, by increasing the reaction temperature. Results are interpreted by considering that the ether would be produced by a concerted mechanism (E2), and the olefin formation could be carried out by both E2 or E1 mechanisms.
Qin, Yingjie; Cabral, Joaquim M. S.
doi: 10.1002/(SICI)1097-4660(199602)65:2<137::AID-JCTB406>3.0.CO;2-Ipmid: N/A
A hollow fiber supported liquid membrane (SLM) process was investigated experimentally and theoretically for the separation of NH3 from aqueous solutions containing NH3 and CO2. DTPA and D2EHPA were used as carriers and n‐decanol was used as a diluent in this process. The membrane stripping experiments, as well as the extractive equilibrium experiments, indicate that DTPA is a better carrier than D2EHPA in relation to the increase in the NH3 stripping rate. The influence of operating conditions, such as flow rate, the ratio of NH3 to CO2, and carrier concentration, on the membrane stripping rate were examined. The experimental data demonstrate that the NH3 stripping rate by an SLM process is not significantly influenced by the amount of CO2 present, as is that by the supported gas membrane. To predict the stripping of NH3 from solutions containing NH3 and CO2, a mathematical model incorporating chemical equilibria and Nernst–Planck diffusion was developed to describe the mass transport. The experimental data suggested that the SLM process can effectively strip NH3 from aqueous solutions containing NH3 and CO2.
Kamboj, Ramesh C.; Raghav, Neera; Nandal, Anita; Singh, Hari
doi: 10.1002/(SICI)1097-4660(199602)65:2<149::AID-JCTB378>3.0.CO;2-3pmid: N/A
Cathepsin B (EC 3.4.22.1), purified from goat brain, was immobilized in calcium alginate beads in the presence of bovine serum albumin. The immobilized enzyme retained ∼63% of the original activity and could be used for seven successive batch reactions with retention of 22–30% of the initial activity. Immobilized cathepsin B hydrolysed α‐N‐benzoyl‐D,L‐arginine‐β‐naphthylamide (BANA) maximally at pH 5·5, exhibiting a shift of 0·5 pH unit from that of the soluble enzyme (pH optima 6·0). It showed enhanced stability in acidic as well as alkaline environments in comparison to the free enzyme. The optimal temperature and thermal stability were not altered significantly after immobilization. The Km value for the immobilized enzyme was two‐fold higher than for the soluble enzyme.
Tsai, Shau‐Wei; Liu, Bih‐Yuan; Chang, Chun‐Sheng
doi: 10.1002/(SICI)1097-4660(199602)65:2<156::AID-JCTB415>3.0.CO;2-Fpmid: N/A
The kinetics of enantioselective esterification of racemic Naproxen with trimethylsilyl methanol by Candida cylindracea lipase (triacylglycerol ester hydrolases, EC 3.1.1.3) were examined in various organic mixtures. The effects of solvent hydrophobicity on the activity, selectivity and stability of the enzyme and Naproxen solubility were investigated. Parabolic correlation for the dependence of the kinetic constants and Naproxen solubility on solvent hydrophobicity was found. A mixture of 60% isooctane and 40% toluene (v/v) was selected as the best reaction medium in which improvement of (S)‐Naproxen ester productivity was obtained.
doi: 10.1002/(SICI)1097-4660(199602)65:2<163::AID-JCTB416>3.0.CO;2-Cpmid: N/A
Two distinct lipase forms were obtained from Candida rugosa lipase by Phenyl Sepharose hydrophobic interaction and DEAE Sepharose ion exchange chromatography, L1 at 45% yield and L2 at 4·7% yield. Both purified lipases were able to catalyse esterification of 1‐butanol and oleic acid and trans‐esterification of 2‐ethyl‐1‐hexanol and rapeseed oil. Lipase L1 gave a 98% yield for esterification over 12 h and a 99% conversion of rapeseed oil for trans‐esterification over 24 h. The minor fraction L2 gave a 97% yield for esterification over 30 h and only a 79% conversion for trans‐esterification over 24 h. The superiority of fraction L1, especially in trans‐esterification, could be clearly shown by reversed phased HPLC analysis. Sodium deoxycholate treatment of the purified main lipase L1 considerably improved the initial rate in both esterification and trans‐esterification.
Miyazawa, Mitsuo; Okamura, Shigeaki; Kameoka, Hiromu
doi: 10.1002/(SICI)1097-4660(199602)65:2<171::AID-JCTB396>3.0.CO;2-6pmid: N/A
Biological reduction of alkylcyclohexanones by Glomerella cingulata was studied. With this organism regioisomeric 2‐, 3‐ or 4‐methylcyclohexanone gave the corresponding cis‐ and trans‐methylcyclohexanols. The major metabolites of (±)‐2‐ and (±)‐3‐methylcyclohexanone were cis‐2‐ and cis‐3‐methylcyclohexanol. On the other hand, 4‐methylcyclohexanone yielded mainly the trans‐4‐methylcyclohexanol. In addition, the metabolites from (±)‐2‐ and (±)‐3‐methylcyclohexanone indicated enantioselective reduction by specific optical rotation of the products. The enantiomeric excesses of the microbiological reduction products were determined by NMR spectra of (+)‐MTPA‐esters of the alcohols produced. The reduction of (±)‐2‐methylcyclohexanone was stereospecific, with the (2R)‐ketone being converted to the corresponding (+)‐cis‐2‐methylcyclohexanol (1S‐2R); absolute configuration, 92% e.e. On the other hand, the enantiomeric excess of the major metabolite of (±)‐3‐methylcyclohexanone was (−)‐cis‐3‐methylcyclohexanol (1S‐3R); absolute configuration, 33% e.e.
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