Modeling and optimization of lipase-catalyzed synthesis of dilauryl adipate ester by response surface methodology

BACKGROUND: Adipate esters are used as low-temperature and low-viscosity plasticizers for polyvinyl chloride and its copolymers. In this work, optimization of lipase-catalyzed production of dilauryl adipate was carried out using response surface methodology (RSM) based on a four-factor-five-level central composite rotatable design (CCRD). Immobilized lipase from Candida antarctica (Novozym 435) was used as catalyst in this reaction. Various reaction parameters affecting the synthesis of adipate ester, including alcohol/acidmolar ratio, amount of enzyme, temperature and reaction time, were investigated. RESULTS: Statistical analysis showed that the amount of enzyme was less significant than the other three factors. The optimal conditions for the enzymatic reaction were obtained at 5.7:1 substrate molar ratio using 0.18 g of enzyme at 53.1 ◦C for 282.2min. Under these conditions the esterification percentage was 96.0%. CONCLUSIONS: The results demonstrated that response surface methodology can be applied effectively to optimize the lipase-catalyzed synthesis of adipate ester. The optimum conditions can obtained be used to scale up the process

Lipase-catalyzed dimethyl adipate synthesis: response surface modeling and kinetics

Dimethyl adipate (DMA) was synthesized by immobilized Candida antarctica lipase B-catalyzed esterification of adipic acid and methanol. To optimize the reaction conditions of ester production, response surface methodology was applied, and the effects of four factors namely, time, temperature, enzyme concentration, and molar ratio of substrates on product synthesis were determined. A statistical model predicted that the maximum conversion yield would be 97.6%, at the optimal conditions of 58.5°C, 54.0 mg enzyme, 358.0 min, and 12:1 molar ratio of methanol to adipic acid. The R2 (0.9769) shows a high correlation between predicted and experimental values. The kinetics of the reaction was also investigated in this study. The reaction was found to obey the ping-pong bi-bi mechanism with methanol inhibition. The kinetic parameters were determined and used to simulate the experimental results. A good quality of fit was observed between the simulated and experimental initial rates

High energy density supercapacitors from lignin derived submicron activated carbon fibers in aqueous electrolytes

Highly porous submicron activated carbon fibers (ACFs) were robustly generated from low sulfonated alkali lignin and fabricated into supercapacitors for capacitive energy storage. The hydrophilic and high specific surface ACFs exhibited large-size nanographites and good electrical conductivity to demonstrate outstanding electrochemical performance. ACFs from KOH activation, in particular, showed very high 344 F g-1 specific capacitance at low 1.8 mg cm-2 mass loading and 10 mV s-1 scan rate in aqueous electrolytes. Even at relatively high scan rate of 50 mV s-1 and mass loading of 10 mg cm-2, a decent specific capacitance of 196 F g-1 and a remarkable areal capacitance of 0.55 F cm-2 was obtained, leading to high energy density of 8.1 Wh kg-1 based on averaged electrodes mass. Furthermore, over 96% capacitance retention rates were achieved after 5000 charge/discharge cycles. Such excellent performance demonstrated great potential of lignin derived carbons for electrical energy storage. © 2014 Elsevier B.V. All rights reserved.

The Human Rights Philosophy: Support And Opposition Among Undergraduate Social Work Students

In response to the rising importance of human rights, social work student attitudes toward human rights and the effect of human rights course content on these attitudes were assessed. Descriptive results from a sample of 77 students pointed to a few areas of low support for the human rights philosophy, specifically rights related to mental illness, juvenile justice, asylum seeking, same-sex marriage, and the death penalty. Wilcoxon signed-rank tests suggest that human rights content infusion was successful in fostering higher levels of support for some but not all human rights

An Evaluation Of Youth Mental Health First Aid Training In School Settings

Youth Mental Health First Aid (YMHFA) is a training program designed to help adults working with children and adolescents identify and respond to youth who are experiencing mental health problems or are in crisis. YMHFA is being implemented in a number of educational, child welfare, and juvenile justice settings across the country with little evidence of its effectiveness. As part of a broader mental health program implemented in five schools in a southeastern county in the USA, YMHFA was provided to school personnel over a 2-year period. This study presents the results of a pretest/posttest evaluation of the YMHFA training. In general, results provide preliminary evidence of the effectiveness of the YMHFA training. More specifically, results highlight the importance of YMHFA training for personnel who have never received mental health training/education and for those who do not have experience working with vulnerable youth populations

A Silenced Population: Uncovering Correlates Of Suicidal-Related Behavior Among Deaf And Hard-Of-Hearing Youth

Background: Given challenges that exceed the normal developmental requirements of adolescence, deaf and hard-of-hearing (DHH) youth are believed to be at elevated risk for engaging in suicide-related behavior (SRB). Unfortunately, little is known about the mechanisms that put these youth potentially at risk. Aims: To determine whether peer relationship difficulties are related to increased risk of SRB in DHH youth. Method: Student records (n = 74) were retrieved from an accredited educational center for deaf and blind students in the United States. Results: Peer relationship difficulties were found to be significantly associated with engagement in SRB but not when accounting for depressive symptomatology. Limitations: The restricted sample limits generalizability. Conclusions regarding risk causation cannot be made due to the cross-sectional nature of the study. Conclusion: These results suggest the need for future research that examines the mechanisms of the relationship between peer relationship difficulties, depression, and suicide risk in DHH youth and potential preventive interventions to ameliorate the risks for these at-risk youth