Immobilized enzyme

About: Immobilized enzyme is a research topic. Over the lifetime, 15282 publications have been published within this topic receiving 401860 citations.

Enzymatic hydrolysis of soil organic phosphorus by immobilized phosphatases

Abstract: In order to estimate the role of phosphatases in maintaining the potential bioavailable P pool in soils, water and 0.4 M NaOH soil extracts were incubated with immobilized acid phosphatase, alkaline phosphatase, phospholipase and nuclease, separately, and in combinations. Immobilized nuclease at an optimum pH of 7.0 hydrolyzed the most soluble unreactive P (SUP) both in water and 0.4 M NaOH extracts. The combination of immobilized alkaline phosphatase and nuclease increased the hydrolysis of SUP at pH 7.0 by up to 61% in 0.4 M NaOH extracts relative to that due to immobilized nuclease alone. The combination of immobilized acid phosphatase and nuclease, however, did not increase the hydrolysis of SUP in either extract relative to that due to immobilized nuclease alone. Immobilized alkaline phosphatase and phospholipase increased the hydrolysis of SUP at pH 7.0 by up to 62% in 0.4 M NaOH extracts relative to that due to immobilized phospholipase alone. Similarly, immobilized acid phosphatase and phospholipase increased the hydrolysis of SUP at pH 7.0 by up to 49% in 0.4 M NaOH extracts relative to that due to immobilized phospholipase alone. The similarities in the optimum pH of indigenous phosphatases in soils and the immobilized phosphatases used in this study, immobilized on positively charged supports, suggests that indigenous phosphatases could be immobilized on positively charged surfaces in soils.

Low-Potential Detection of Endogenous and Physiological Uric Acid at Uricase-Thionine-Single-Walled Carbon Nanotube Modified Electrodes

Abstract: This work develops and validates an electrochemical approach for uric acid (UA) determinations in both endogenous (cell lysate) and physiological (serum) samples This approach is based on the electrocatalytic reduction of enzymatically generated H2O2 at the biosensor of uricase−thionine−single-walled carbon nanotube/glassy carbon (UOx−Th−SWNTs/GC) with the use of Th−SWNTs nanostructure as a mediator and an enzyme immobilization matrix The biosensor, which was fabricated by immobilizing UOx on the surface of Th−SWNTs, exhibited a rapid response (ca 2 s), a low detection limit (05 ± 005 μM), a wide linear range (2 μM to 2 mM), high sensitivity (∼90 μA mM−1 cm−2), as well as good stability and repeatability In addition, the common interfering species, such as ascorbic acid, 3,4-dihydroxyphenylacetic acid, 4-acetamidophenol, etc, did not cause any interference due to the use of a low operating potential (−400 mV vs saturated calomel electrode) Therefore, this work has demonstrated a simple and effecti

Characterization of gelatin-immobilized pigeonpea urease and preparation of a new urea biosensor.

Abstract: Urease purified from pigeonpea seeds was immobilized on gelatin beads via cross-linking with glutaraldehyde The maximum immobilization (75%) was observed at 30 mg/ml gelatin, 0414 mg of enzyme/bead, 1% (v/v) glutaraldehyde and 4 degrees C Beads stored in 50 mM Tris/acetate buffer (pH 73) at 4 degrees C showed a half-life of 240 days and there was practically no leaching of enzyme (less than 2%) over a period of 30 days These beads can be reused more than 30 times (with 24 h intervals) without much loss of enzyme activity (ie less than 11%) The immobilized urease showed a shift in its optimum pH from 73 to 65 in Tris/acetate buffer Optimum temperature also shifted from 47 to 65 degrees C compared with the soluble enzyme Gelatin-immobilized pigeonpea urease had a higher K(m) (83 mM) than that of the soluble enzyme (30 mM) The time-dependent temperature inactivation pattern was also found to change from biphasic to monophasic kinetics The immobilized beads were used for the preparation of a new urea biosensor with a response time of less than 2 min At least 14 samples of urea can be measured with this biosensor within an hour The beads, as well as the biosensor, were used to analyse the urea content in clinical samples from the local clinical pathology laboratories The results obtained with the biosensor were strikingly similar to those obtained with the various commonly employed biochemical/autoanalyzer(R) methods used These immobilization studies also have a potential role in haemodialysis machines that maintain the urea level in kidney patients and in the construction of a portable/wearable kidney The easy availability of the pigeonpea urease, the ease of its immobilization on gelatin and a significantly lower cost of the urease described in the present study makes it a suitable product for future applications in therapeutics and diagnostics

Methods for the immobilization of lipases and their use for ester synthesis

Abstract: The lipase from Pseudomonas fluorescens was immobilized onto five different carriers: celite, octyl-silica, aminopropyl-silica, gluterdialdehyde-activated silica and Eupergit C250L. Activities and operational stabilities of the prepared catalysts were compared using the enantioselective acylation of (R,S)-1-phenylethanol by vinyl acetate as acyl donor and t -butylmethyl ether with variable water content (0.038-0.97% v/v) as reaction medium. The above carriers provide catalysts with widely different specific activities ranging from excellent 25 mmol/h mg protein (celite) to 0.07 mmol/h mg protein (glutardialdehyde-activated silica) on the lower end. The lipase immobilized onto Eupergit C250L exhibited the best operational stability among the catalysts studied. It retained 30% of its initial activity after 11 cycles of application, each with a duration between 2 and 6 h.