Novozym® 435-catalyzed production of ascorbyl oleate in organic solvent ultrasound-assisted system

Hydrolysis of macauba kernel oil: ultrasound application in the substrates pre-emulsion step and effect of the process variables

The main goal of the present work was to evaluate the application of ultrasound as a previous step to promote the substrates pre-emulsion in the hydrolysis reaction of macauba kernel oil (MKO). The ultrasound effect on the substrates pre-emulsion was evaluated on the free fatty acid (FFA) content, as well as the process variables (reaction time, percentage of catalyst Lipozyme® RM IM, and buffer solution). Reactions carried out with the substrates pre-emulsion presented higher FFA production, up to a 40 wt% increase in 1 hour of reaction, yielding 80 wt% of FFAs in 8 hours. The use of catalyst in the reaction medium, from 5 to 15 wt%, favored the FFAs production in 2 hours of reaction. Addition of 25 to 100 wt% of buffer solution led to 86 wt% of FFAs in 4 hours of reaction. Enzyme recycling resulted in a slight decrease in the FFA content, although the catalyst had maintained 85% of its initial activity after 30 h of use. Therefore, the ultrasound pre-emulsion previous step allowed a more efficient hydrolysis reaction of MKO, leading to an increase of up to 40 wt% on the FFA content, when compared to the hydrolysis without such step.

A reactor designed for the ultrasonic stimulation of enzymatic esterification

A laboratory scale ultrasonic flow reactor capable of enhancing enzymatic reactions has been built and characterized using as a model reaction the enzymatic synthesis of isoamyl acetate using Lipozyme 435 immobilized on a macroporous anion exchange resin. The efficiency of the reactor was determined in relation to ultrasonic power density (measured by 4-nitrophenol dosimetry), position of ultrasonic horn and temperature. The results show that ultrasound can enhance the process efficiency and also reduce the reaction time.

An investigation of lipase catalysed sonochemical synthesis: A review

Ultrasonic irradiation has recently gained attention of researchers for its process intensification in numerous reactions. Earlier ultrasound was known for its application either to deactivate enzyme activity or to disrupt the cell. However, in recent years, practice of ultrasonic irradiation began to emerge as a tool for the activation of the enzymes under mild frequency conditions. The incorporation of ultrasound in any of enzymatic reactions not only increases yield but also accelerates the rate of reaction in the presence of mild conditions with better yield and less side-products. To attain maximum yield, it is crucial to understand the mechanism and effect of sonication on reaction especially for the lipase enzyme. Thus, the influence of ultrasound irradiation on reaction yield for different parameters including temperature, enzyme concentration, mole ratio of substrates, solvents ultrasonic frequency and power was reviewed and discussed. The physical effect of cavitation determined by bubble dynamics and rate of reaction through kinetic modelling also needs to be assessed for complete investigation and scale up of synthesis. Thus, prudish utilisation of ultrasound for enzymatic synthesis can serve better future for sustainable and green chemistry.

Advances in Green Organic Sonochemistry

Over the past 15 years, sustainable chemistry has emerged as a new paradigm in the development of chemistry. In the field of organic synthesis, green chemistry rhymes with relevant choice of starting materials, atom economy, methodologies that minimize the number of chemical steps, appropriate use of benign solvents and reagents, efficient strategies for product isolation and purification and energy minimization. In that context, unconventional methods, and especially ultrasound, can be a fine addition towards achieving these green requirements. Undoubtedly, sonochemistry is considered as being one of the most promising green chemical methods (Cravotto et al. Catal Commun 63: 2-9, 2015). This review is devoted to the most striking results obtained in green organic sonochemistry between 2006 and 2016. Furthermore, among catalytic transformations, oxidation reactions are the most polluting reactions in the chemical industry; thus, we have focused a part of our review on the very promising catalytic activity of ultrasound for oxidative purposes.