Immobilised cellulolytic and hemicellulolytic enzymes from Macrophomina phaseolina

Cellulolytic enzymes from Macrophomina phaseolina were immobilised in acrylamide polymer. The immobilised enzyme preparation showed activity towards filter paper and cotton. However, the degree of hydrolysis of highly organised cellulose, particularly cotton, appears to be low in comparison with that of soluble substrate. The kinetic studies of immobilised enzymes indicated the presence of diffusional limitations by the increase in V_max as the particle size decreased. The operational studies suggested that the immobilised enzymes retained the original activities up to 25–29 times in the reuse cycle.     

人工合成膜——生物催化剂固定化的新载体

合成膜在生化工程中最新应用是作为生物催化剂固定化的新载体。人工膜用于固定化生物催化剂近年来引起了人们的极大关注并获得了广泛地研究。不同的膜体系及运行方式与生物催化剂相结合构成了多种膜生化反应器。本文介绍并综述了膜固定化生物催化剂的原理、方法分类和应用。     

Detoxification of cyanide by immobilised fungi

Cyanide detoxification was studied by immobilisation of fungal mycelia that had been induced to form cyanide hydratase (formamide hydrolyase) which is able to hydrolyse cyanide to formamide. The fungal pathogens of cyanogenic plants, Stemphylium loti, Gloeocercospora sorghi and Fusarium moniliforme were immobilised using polyelectrolyte flocculating agents. The effect of immobilisation on the enzymic properties of S. loti and G. sorghi were investigated. The apparent K_m values increased from 21.0 mmol and 25.5 mmol KCN to 43.5 mmol and 71.0 mmol KCN, respectively. The pH profile for the two enzymes widened on immobilisation. The stoichiometry of 1:1 cyanide utilisation to formamide formation was retained on immobilisation, with complete conversion of 70 mmol KCN in 120 min by 0.12 g dry wt of S. loti and in 6 min by 0.13 g dry wt of G. sorghi. When the two fungi were stabilised by immobilisation, and tested in column reactors containing 1.2 g dry wt of S. loti and 1.3 g dry wt of G. sorghi, they completely converted cyanide (70 mmol; added continuously at 7.5 ml h^?1) into formamide for 2 days and 30 days, respectively. Stability was enhanced by inclusion of 1.0 mmol glucose in the 70 mmol KCN solution, by a further 10 h for S. loti and an extra 10 days for G. sorghi. Operational stabilities of immobilised G. sorghi (1.3 g dry wt) and F. moniliforme (1.0 g wet wt) in column reactors, with 100 % cyanide conversion, at varying flow rates was investigated. G. sorghi was stable for 15, 10 and 2 days whereas F. moniliforme was only stable for 48, 20 and 10 h at 30, 60 and 120 ml h^?1 flow rates respectively.     

Removal efficiency of heavy oil by free and immobilised microorganisms on laboratory‐scale

This study explored free and immobilised microorganisms to degrade heavy oil. Two oil‐degrading bacterial strains (W‐1 and W‐2) were isolated from heavy oil wastewater samples collected from Shengli Oil Field in China. W‐1 and W‐2, identified as Rhosococcus sp. and Bacillus cereus sp., respectively, were tested for their growth behaviour and optimal growth conditions in the laboratory. The obtained results showed that the optimal growth conditions for W‐1 and W‐2 were identified as pH of 8, temperature of 40°C, and salinity of 2% and 4%, respectively. The environmental conditions affecting oil‐degrading efficiency by W‐1 and W‐2 were optimised in the media containing 0.3% heavy oil. The results showed that the optimal degradation and optimal growth conditions were similar, and the oil degradation rates of W‐1 and W‐2 were about 34.6% and 45.3%, respectively after 5 days. W‐1 and W‐2 capable of degrading oil was immobilised in calcium alginate gel beads containing active carbon and used for degradation of heavy oil. The heavy oil biodegradability of immobilised bacteria improved dramatically, compared with that of the free ones. The heavy oil biodegradation rates of immobilised W‐2 were found to be maximal at the same optimal growth conditions of pH, temperature, and salinity as the free ones. The best biodegradation rate of immobilised W‐2 reached above 78%, which is 33% than that of the free W‐2. © 2011 Canadian Society for Chemical Engineering     

The influence of free fatty acid intermediate on biodiesel production from soybean oil by whole cell biocatalyst

The whole cell of lipase-producing Rhizopus oryzae was employed as biocatalyst for transesterification of soybean oil containing oleic acid. The free fatty acid (FFA) intermediate, playing an important role in the kinetics of transesterification of soybean oil, was thoroughly investigated and characterized. The conversion was more than 97% at the initial FFA content of 5.5%. A high content of FFA could protect the lipase from denaturation. The 34.6 percent of FFA with the optimal 26-mg mL⁻¹ methanol resulted in a specific reaction rate of 420 mg h⁻¹g-dry cell⁻¹. In addition, the methanol/FFA ratio at 0.83-1.7 provides a good indication of the fatty acid methyl esters conversions for different initial FFA contents. In the transesterification process, more FFA intermediate present would become beneficial to conversion of retrograde feedstock to biodiesel. The immediately generated and original FFA content become the major rate-determining factor in the FFA-mixed transesterification process.     

Use of the Exponential Model of Enzyme Decay to Plan a Strategy for Enzymatic Batch Reactions and to Assess the Industrial Applicability of Immobilised Enzyme Preparations

This paper is concerned with the development of a model to plan a strategy for an enzymatic batch process whereby the enzyme is subjected to deactivation as described by the exponential (first-order) decay model. The particular system used was the enzymatic hydrolysis of penicillin to 6-aminopenicillanic acid, but the model can be utilised with other batch systems, provided that decay of the immobilised enzyme preparation is described by the exponential decay model. The model developed is eminently practical and simple, and several examples of its application are given. Experimental data obtained in a small pilot plant batch recirculated reactor could, on average, be well fitted by this model.     

Studies of L-phenylalanine production by immobilised aminoacylase in stabilized calcium alginate beads

Aminoacylase I (EC 3.5. 1.14) was immobilised by entrapment in uncoated calcium alginate beads and calcium alginate beads coated with chitosan, polyethyleneimine and polyethyleneimine-glutaraldehyde for the production of L-phenylalanine by the hydrolysis of a racemic mixture of N-acetyl-DL-phenylalanine. The operational stability, thermal stability, effects of pH and temperature and kinetic constants, K_m and V_max values of free and immobilised enzymes were studied. Scanning electron micrographs revealed differences in the structures of the surfaces of coated and uncoated beads. Chitosan-coated calcium alginate beads was found to be the best among the immobilised systems studied. The activity and the optimum temperature of immobilised aminoacylase were higher than those of the free enzyme. In addition, the beads showed stable activity under operational conditions. The immobilised aminoacylase lost about 20% of its initial activity after ten cycles of reuse. Polyethyleneimine and polyethyleneimine-glutaraldehyde treatments were also found to enhance the operational stability of the enzyme but its activity was greatly reduced.     

极具前景的炼油新催化材料

介绍了新结构分子筛、纳米催化材料、生物催化剂、杂多酸、离子液体、非晶态合金、过渡金属氮化物和均相催化剂等极具前景的炼油新催化材料。     

Modelling lipase‐catalysed transesterification of fats containing n‐3 fatty acids monitored by their solid fat content

Transesterification of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA), catalysed by a commercial immobilised thermostable lipase from Thermomyces lanuginosa, was carried out batch‐wise. Experiments were performed, following central composite rotatable designs (CCRDs) as a function of reaction time, temperature and media formulation. Mixtures of palm stearin, palm kernel oil and a commercial concentrate of triacylglycerols rich in n‐3 PUFA (“EPAX 2050TG” in CCRD‐1 and “EPAX 4510TG” in CCRD‐2) were used. The time‐course of transesterification was indirectly followed by the solid fat content (SFC) values of the blend at 10 °C, 20 °C, 30 °C and 35 °C. A decrease in all SFC values of the blends at 10 °C, 20 °C, 30 °C and 35°C was observed upon transesterification. The SFC_{10 °C} and SFC_{20 °C} of transesterified blends varied between 18 and 48 and SFC_{35 °C} between 6 and 24. These values fulfil the technological requirements for the production of margarines. Under our conditions, lipid oxidation may be neglected. However, the accumulation up to 8.3% free fatty acids in reaction media is a problem to overcome. The development of response surface models, describing both the final SFC value and the SFC decrease, will allow predicting results for novel proportions of fats and oils and/or a novel combination time‐temperature.