Utilization of two modified layered doubled hydroxides as supports for immobilization of Candida rugosa lipase.

In this study, two synthetic layered doubled hydroxides (LDH), including Mg/Al-CO3-LDH (LDH1) and Zn/Al-CO3-LDH (LDH2), were prepared using the co-precipitation method and modified with sodium dodecyl sulfate to be utilized as carriers for immobilization of Candida rugosa lipase via the adsorption. The activity of prepared biocatalysts was measured in the olive oil hydrolysis. The effects of lipase concentration, pH, storage stability and thermal resistance of the samples were also studied. The maximum activity was obtained at pH 6.0 for immobilized lipase on modified LDHs with monolayer surfactants, including MLDH1 (0.922 U/mg) and MLDH2 (0.744 U/mg), respectively. The remained activities for immobilized lipase on MLDH1 and MLDH2 after 24 h incubation at 60 °C were 85% and 81%, respectively. During the 25days of storage at 4 °C, immobilized lipases on MLDH1, MLDH2, and free lipase kept 87%, 86%, and 70% of their initial activities. The residual activities for immobilized lipase on MLDH1 and MLDH2 after reusing for ten cycles were 72% and 67% of their initial activities. Adsorption parameters for sorption of lipase on all supports were fitted to the Freundlich and Langmuir isotherms. Kinetic parameters obtained from the Michaelis-Menten equation on MLDH1 and MLDH2 were comparable to free enzyme.

Performance evaluation of a bipolar electrolysis/electrocoagulation (EL/EC) reactor to enhance the sludge dewaterability.

The present study aimed to evaluate the performance of a bipolar electrolysis/electrocoagulation reactor designed to enhance the sludge dewaterability. The reactor was 15 L in volume, with two series of plates used in it; Ti/RuO(2) plates for the electrolysis of the sludge, and also aluminum and iron plates for electrocoagulation process. The dewaterability of the sludge was determined in terms of its capillary suction time (CST) and specific resistance to filtration (SRF), while the degree of sludge disintegration was determined based on the value of degree of sludge disintegration (DD(SCOD)). The maximum reduction in CST and SRF was observed at a detention time of 20 min and a voltage of 30 V. However, increasing of both detention time and voltage significantly increased the values of CST and SRF even to an extent that they both exceeded those of the untreated sludge. The optimal degree of sludge disintegration achieved by the present study was 2.5%, which was also achieved at a detention time of 20 min and a voltage of 30V. As reported previously, increased DD(SCOD) values led to increasing CST and SRF values, due primarily to the disruption of the sludge flocs. According to the results from the present study, it can be concluded that simultaneous application of electrocoagulation and electrolysis is effective in enhancing the sludge dewaterability, because electrocoagulation helps to achieve a higher degree of sludge disintegration while maintaining the desired sludge dewaterability.

Effect of short term treatment of L-carnitine on tissue ACE activity in streptozotocin-induced diabetic rats.

Diabetes is commonly related to the both microvascular as well as macrovascular complications. It appears that both metabolic and hemodynamic factors interact to create these problems. In this study the effects of orally administered L-carnitine, a natural amino acid, on ACE activity in streptozotocin (STZ)-induced diabetic rats were investigated. Streptozotocin (60mg/kg body weight) was given intraperitoneally. Fifty male Sprague-Dawley rats were divided into four groups: untreated normal (C), L-carnitine treated normal (CT), untreated diabetics (D), L-carnitine-treated diabetics (DT). CT and DT received daily L-carnitine 1g/kg orally for 3 weeks after inducing diabetes. The ACE activities in aorta, heart and kidney homogenates was measured at the end of 3 weeks. They were significantly increased in D compared to C group (P<0.05) and significantly decreased in aorta, heart and kidney in DT compared to D group. In conclusion, L-carnitine can reduce tissue ACE activity in aorta, heart and kidney in streptozotocin diabetic rats, which may be due to higher NO production.