Production of fumaric acid with immobilized biocatalysts

Immobilization ofRhizopus arrhizus mycelium improved fumaric acid production. The optimum conditions for fumaric acid production with immobilized cells were investigated using a statistical experimental design. Substrate concentration, carbon:nitrogen ratio, and residence time were chosen as independent variables. In the repeated batch shake flask fermentation, the fumaric acid yield from xylose was as much as 3.5 times higher with immobilized mycelium than with free mycelium. Polyurethane foam cubes, in this case, gave better results than nylon net cubes as a carrier.     

Selection and microencapsulation of an “NADH-oxidizing” bacterium and its use for NAD regeneration

An alternative approach to the regeneration of coenzymes is described here using immobilized microorganisms possessing “NADH-oxidase” function. Bacteria containing NADH-oxidase activity are immobilized by microencapsulation within artificial cells. In this form, the microencapsulated bacteria can recycle NADH back to NAD in the presence of molecular oxygen as an electron acceptor. The only byproduct of the recycling reaction is water. In order to perform the biological regeneration of NAD, the activity of NADH-oxidase was investigated in 13 strains of aerobic bacteria and yeast. The NADH-oxidizing bacteriaLeuconostoc mesenteroides exhibited the highest activity among the microorganisms tested. The permeabilized bacteria showed 10% of their initial activity after microencapsulation. Light and electron microscopy studies of bacteria loaded microcapsules have been done. Enzymatic properties of microcapsule-immobilized bacteria were investigated in comparison with those of the free enzyme complex.Leuconostoc mesenteroides, containing NADH-oxidase, has been microencapsulated together with 3α-hydroxysteroid dehydrogenase (3α-HSDH) for stereospecific steroid oxidation. In a batch reactor, 2 mg of NAD, with recycling, allowed the same substrate consumption as 4.4 mg of NAD without recycling. The microencapsulated system can be used repeatedly. The system is functional for 10 h, during which time each molecule of NAD has been used 7.6 times.     

Continuous production of butanol with immobilized cells ofClostridium acetobutylicum

Spores ofClostridium acetobutylicum were immobilized in calcium alginate. An active gel preparation was obtained after outgrowth of the spores to vegetative cells within the gel matrix. A 100 mL column containing the immobilized cells was used for continuous production. At steady-state conditions the productivity of butanol was 67 g/L reactor volume/day.     

Lactic acid production from cheese whey by immobilized bacteria

The performance of immobilized Bifidobacterium longum in sodium alginate beads and on a spiral-sheet bioreactor for the production of lactic acid from cheese whey was evaluated. Lactose utilization and lactic acid yield of B. longum were compared with those of Lactobacillus helveticus. B. longum immobilized in sodium alginate beads showed better performance in lactose utilization and lactic acid yield than L. helveticus. In the spiral-sheet bioreactor, a lactose conversion ratio of 79% and lactic acid yield of 0.84 g of lactic acid/g of lactose utilized were obtained during the first run with the immobilized L. helveticus. A lactose conversion ratio of 69% and lactic acid yield of 0.51 g of lactic acid/g of lactose utilized were obtained during the first run with immobilized B. longum in the spiral-sheet bioreactor. In producing lactic acid L. helveticus performed better when using the Spiral Sheet Bioreactor and B. longum showed better performance with gel bead immobilization. Because B. longum is a very promising new bacterium for lactic acid production from cheese whey, its optimum fermentation conditions such as pH and metabolic pathway need to be studied further. The ultrafiltration tests have shown that 94% of the cell and cheese whey proteins were retained by membranes with a mol wt cutoff of 5 and 20 KDa.     

固载Ru基催化剂上二氧化碳加氢合成甲酸的研究(IV): 反应机理

探讨了在CO₂加H₂合成HCOOH过程中原位合成的固载Ru基催化剂的可能结构、CO₂的活化方式以及可能的反应机理. 在反应中, 固载Ru配合物中的一个P配体首先解离, 被质子型溶剂ROH取代而生成循环活性物质, 然后CO₂正插入Ru—H键生成甲酸酯配合物, 之后甲酸酯配合物中的Ru—O₂CH键被H₂氢解生成HCOOH, 而本身重新转化为活性物质, 完成催化循环.     

Enzyme thermistors for process monitoring and control

In today’s biotechnology there is an increasing demand for appropriate analytical systems for process control. At present the most widely used control systems are based on measurements of pH, pO₂, and pCO₂. Such systems do not allow the direct measurement of substrates and products. To overcome this drawback sensors such as enzyme thermistors and enzyme electrodes have been designed and their development into industrial useful sensors for monitoring and controlling is the subject of active research.     

流动注射分析法测定固定化酶的催化活力

本文介绍了脲酶的固定方法以及用流动注射分析法测定固定化酶的催化活力，测得脲的平均转化率为９５．０％。     

A preliminary study for isolation of catalytic antibodies by histidine ligand affinity chromatography as an alternative to conventional protein A/G methods

Catalytic autoimmune antibodies from the sera of lupus patients were purified using histidyl-aminohexyl-Sepharose gel and compared with the antibodies purified with protein A and protein G affinity chromatography. The IgG preparations from the histidine affinity column had a much higher catalytic activity in hydrolyzing the peptide substrate Pro-Phe-Arg-methyl-coumarinamide compared to the antibodies obtained by the conventional protein A/G method. This preservation of catalytic activity is attributed to the gentle buffer conditions used in the histidine ligand method that allowed the integrity of three-dimensional structure of purified catalytic antibodies. Thus, histidine affinity offer a superior method for isolating autoimmune catalytic antibodies.     

Site-specific immobilization of flavin adenine dinucleotide on indium/tin oxide electrodes through flavin adenine amino group

A Mannich-type reaction was used to attach flavin adenine dinucleotide (FAD) covalently to aminosilane derivatized indium/tin oxide-coated glass plates. The aminosilane was activated with formaldehyde to give an intermediate that attached specifically to the adenine amino group of FAD. The presence of the intermediate also was demonstrated by coupling hydroquinone to the formaldehyde activated support. The immobilized FAD and hydroquinone were characterized by cyclic or differential pulse voltammetry. The immobilized FAD was shown to reduce the overpotential for NADH oxidation by 180 mV. In keeping with results for FAD on glassy carbon, FAD attached to indium/tin oxide at the adenine amino group did not lead to reconstitution of activity with apoglucose oxidase. On leave from University of Madras, India.     

纳米ZnO增强葡萄糖生物传感器的制备和应用

为提高葡萄糖生物传感器的灵敏度,以纳米ZnO与聚乙烯醇缩丁醛(PVB)构成复合固定酶膜基质,采用溶胶-凝胶法固定葡萄糖氧化酶(GOD),用戊二醛进行交联,制成葡萄糖生物传感器。实验结果表明,GOD可牢固地固定在电极表面,在相同葡萄糖浓度下,加入纳米颗粒的电极的电流响应值比未加颗粒的高约100倍,电极重复使用46次后电流响应值仅下降到初始的70%。电极制备方法简单,易于操作。同时对温度、溶液pH值以及溶剂对电极的影响进行了研究,获得了最优的实验条件。