Journal of Chemical Technology & Biotechnology

Miyazawa, Mitsuo; Nobata, Masahiro; Okamura, Shigeaki; Muraoka, Osamu; Tanabe, Genzoh; Kameoka, Hiromu

doi: 10.1002/(SICI)1097-4660(199804)71:4<281::AID-JCTB837>3.0.CO;2-Epmid: N/A

The biotransformation of (±)‐bicyclo(3.3.1)nonane‐2,6‐dione by Aspergillus niger and Glomerella cingulata was investigated. The diketone was reduced to the ketoalcohol 2‐endo‐hydroxy‐bicyclo(3.3.1)nonane‐6‐one and the diol endo,endo‐bicyclo(3.3.1)nonane‐2,6‐diol respectively. Endo,endo‐bicyclo(3.3.1)nonane‐2,6‐diol and ketoalcohols produced by G. cingulata had high optical purity, on the other hand, reduction by A. niger yielded optically active (‐)‐(1R, 2S, 5R, 6S)‐bicyclo(3.3.1)nonane‐2,6‐diol(99·9% e.e.). © 1998 SCI

L'Argentière, Pablo C.; Cagnola, Edgardo A.; Cañón, María G.; Liprandi, Domingo A.; Marconetti, Delia V.

doi: 10.1002/(SICI)1097-4660(199804)71:4<285::AID-JCTB854>3.0.CO;2-Hpmid: N/A

The (NiCl2(NH2(CH2)12CH3)2) complex supported on γ‐Al2O3 produces a catalyst which is considerably more active and sulfur‐resistant for the hydrogenation of cyclohexene carried out in mild conditions than a conventional catalyst obtained from acid solutions of NiCl2 and even than the same complex unsupported. As determined by XPS, the active species is the complex itself, which is stable under the reaction conditions. The higher sulfur‐resistance is attributed to electronic and geometrical effects. The catalyst system is considerably more resistant to poisoning with thiophene than with tetrahydrothiophene. © 1998 SCI

Gharaibeh, S. H.; Moore, S. V.; Buck, A.

doi: 10.1002/(SICI)1097-4660(199804)71:4<291::AID-JCTB856>3.0.CO;2-Cpmid: N/A

The carbonised solid residue of olive mill products, called J‐carbon (0·6–0·7 mm), was compared with Sigma activated carbon (powder) and Chemviron activated carbon (0·6–0·7 mm) in treatment of the effluent of Flexsys' wastewater. The removal of NH3, TOC as non‐specific organics, and six specific leading organic pollutants from Flexsys' wastewater effluent were examined. All three different carbon sources have almost similar behaviour in removing the above pollutants; the removal efficiencies were as follows: Sigma carbon: benzothiazole, 1,2‐dihydro‐2,2,4‐trimethylquinoline, N‐dimorpholinyl ketone, methylsulphyl benzothiazole and methyl‐2‐benzothiazole sulphone 100%>TOC 94%>NH3 82%>tetrachloroethene 50%. Chemviron carbon: benzothiazole, 1,2‐dihydro‐2,2,4‐trimethylquinoline, N‐dimorpholinyl ketone, methylsulphyl benzothiazole and methyl‐2‐benzothiazole sulphone 100%>NH3 87%>TOC 40%>tetrachloroethene 31%. J‐carbon: benzothiazole, methylsulphyl benzothiazole and methyl‐2‐benzothiazole sulphone 100%>NH3 78%>1,2‐dihydro‐2,2,4‐trimethylquinoline 70%>tetrachloroethene 58%>N‐dimorpholinyl ketone 50%>TOC 37%. © 1998 SCI

Stenberg, Kerstin; Tengborg, Charlotte; Galbe, Mats; Zacchi, Guido

doi: 10.1002/(SICI)1097-4660(199804)71:4<299::AID-JCTB858>3.0.CO;2-Zpmid: N/A

Pretreatment of mixed softwoods with SO2 impregnation and steam for production of ethanol has been investigated. The optimal conditions, both for sugar yield and ethanol yield, to assess the effect of inhibitors formed in the pretreatment, have been determined. The parameters investigated were: SO2 concentration (1–6% (w/w) dry matter), temperature (190–230°C) and residence time (2–15 min). After pretreatment, the material was separated into a solid residue and a filtrate. The solid residue was enzymatically hydrolysed with 2% dry matter (w/w). To investigate fermentability, the hydrolysed filtrate was fermented using Saccharomyces cerevisiae. The effects of the different parameters are described by response‐surface modelling. The highest experimental sugar yield of 42·1 g per 100 g dry matter was obtained at 210°C and 5·5 min residence time. Although the fermentabilities were good for all filtrates with yields greater than 90% of the yield obtained in a pure glucose reference solution, the pretreatment has a clear influence on the ethanol production rate. © 1998 SCI

Tsitsimpikou, C.; Stamatis, H.; Sereti, V.; Daflos, H.; Kolisis, F. N.

doi: 10.1002/(SICI)1097-4660(199804)71:4<309::AID-JCTB859>3.0.CO;2-Lpmid: N/A

The acylation of glucose with lauric acid in a reaction catalysed by two Candida lipases and a Mucor miehei lipase in supercritical carbon dioxide (SCCO2) was investigated. A linear dependence of the reaction rate on enzyme concentration was observed. Studies on the effect of temperature on enzyme activity showed that Candida antarctica lipase remains stable at temperatures as high as 70°C. Non‐immobilised Candida rugosa lipase was found to have a temperature optimum at 60°C. The acylation reaction rate depended on the initial water activity of both substrates and enzyme; the optimum was 0·75 for Candida antarctica lipase, 0·53 for Candida rugosa lipase, and between 0·3 and 0·5 for Mucor miehei lipase. Candida rugosa lipase was most active at a molar ratio of sugar: acyl donor of 1: 3, while the optimum ratio was found to increase to 1: 6 when the reaction was catalysed by Candida antarctica and Mucor miehei lipases. © 1998 SCI

Mathys, Renata G.; Kut, Oemer M.; Witholt, Bernard

doi: 10.1002/(SICI)1097-4660(199804)71:4<315::AID-JCTB764>3.0.CO;2-2pmid: N/A

Biocatalytic systems can be used for the regio‐ and stereospecific synthesis of oxidized alkanes and aromatic compounds, such as aliphatic and aromatic alcohols, aldehydes and epoxides. These reactions are typically carried out in two‐liquid phase media. The biocatalyst is usually a natural microorganism, often a Pseudomonas, or a genetically altered host, a Pseudomonas or E. coli recombinant typically, which grows in the aqueous phase, while the substrate and product are present in an organic bulk phase. Oxidation products formed in these systems must be purified after separation of the two liquid phases. We have evaluated the performance of distillation for the separation of the product 1‐octanol by examining a more volatile (octane) and a less volatile (hexadecene) in‐situ extraction system. The separation performance of the two systems has been compared based on recovery efficiency, energy cost and number of required process units. Results showed that a less volatile extractant compared favorably in terms of number of product separation unit steps, decreased operating and energy cost to the use of a more volatile extraction solvent. In addition, a major disadvantage of the more volatile in‐situ extraction process was the coloring of the bottom product of the first distillation step, in which the product is contained in this case. Such modifications can be implemented into an upstream and downstream process of bioconversions to improve the overall system and to reduce downstream processing cost. © 1998 SCI

Mathys, Renata G.; Schmid, Andrew; Kut, Oemer M.; Witholt, Bernard

doi: 10.1002/(SICI)1097-4660(199804)71:4<326::AID-JCTB860>3.0.CO;2-7pmid: N/A

In two‐liquid phase fermentations organic substrates and/or products are dissolved in an apolar phase while microorganisms are suspended in an aqueous medium. The effect of aqueous phase contaminants in the apolar phase on the separation of products from the apolar phase by batch distillation is described in this paper. Various amounts of polar phase, emulsified apolar phase and microorganisms normally present in the two‐liquid fermentation medium were added to the organic phase. The recovery performance of a distillation unit in separating 1‐octanol from such contaminated apolar phases was determined. Further, the bulk properties of the emulsified apolar phase, such as its composition, the nature and the stability of the emulsion were analysed. It was found that the distillation performance is very sensitive to the presence of fermentation media in the organic phase. The energy cost per kg product recovered was almost doubled for only small additions of fermentation impurities. The emulsified apolar phase was shown to be kinetically, but not thermally, stable. Based on these results a suitable apolar phase separation process before distillation can be developed, taking into account energy costs for phase separation and subsequent distillation, to optimize the overall downstream product purification process. © 1998 SCI

Hashim, Mohd A.; Sen Gupta, Bhaskar; Kumar, Seetharam Vijaya; Lim, Roxane; Lim, Song E.; Tan, Chin C.

doi: 10.1002/(SICI)1097-4660(199804)71:4<335::AID-JCTB849>3.0.CO;2-Hpmid: N/A

A study on the clarification of baker's yeast suspension by Colloidal Gas Aphrons (CGA) employing a cationic surfactant, benzyl‐dimethyl‐hexadecyl‐ammonium chloride, is presented. The variables investigated were the CGA flowrate, air flowrate and the yeast concentration. A separation efficiency as high as 95% was achieved at the optimum conditions of air flowrate and feed concentration. The mechanism of particle–bubble attachment was identified and a simple model for the monolayer adsorption of yeast cells on the bubble surface derived. © 1998 SCI

Asif, Mohammad

doi: 10.1002/(SICI)1097-4660(199804)71:4<340::AID-JCTB852>3.0.CO;2-2pmid: N/A

A simple predictive model is presented here to describe the layer inversion behaviour of binary solid–liquid fluidized beds. The model is based on the assumption that the concentrations of the two particle species in the binary bed when normalized with respect to their mono‐component counterparts are linearly related. The comparison of the model predictions with the experimental data available in the literature confirms the applicability of this simple model to predict the inversion phenomenon. © 1998 SCI

Beltrán, Fernando J.; García‐Araya, Juan F.; Álvarez, Pedro M.; Rivas, Javier

doi: 10.1002/(SICI)1097-4660(199804)71:4<345::AID-JCTB869>3.0.CO;2-Cpmid: N/A

This laboratory study was designed to investigate the removal of atrazine (ATZ) and its first main by‐products, deethylatrazine (DEA) and deisopropylatrazine (DIA) by O3/H2O2. At least 76% of the oxidation rate of atrazine is due to free radical reactions. At neutral pH and 20°C, an initial hydrogen peroxide concentration of 10−3 M is optimum to reach a maximum oxidation rate of these compounds. Experimental results of oxidation in the presence of high hydrogen peroxide concentrations allow the mass transfer coefficient of ozonation to be determined. This coefficient, reactor flow analysis and kinetic data obtained have been applied to mol balance equations of atrazine, deisopropylatrazine, deethylatrazine, ozone (both in the gas and water) and hydrogen peroxide to obtain their corresponding concentrations at different conditions. © 1998 SCI