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The named "green chemistry" has been receiving increasing prominence due to its environmentally friendly characteristics. The use of enzymes as catalysts in processes of synthesis to replace the traditional use of chemical catalysts present as main advantage the fact of following the principles of the green chemistry. However, processes of enzymatic nature generally provide lower yields when compared to the conventional chemical processes. Therefore, in the last years, the ultrasound has been extensively used in enzymatic processes, such as the production of esters with desirable characteristics for the pharmaceutical, cosmetics, and food industry, for the hydrolysis and glycerolysis of vegetable oils, production of biodiesel, etc. Several works found in the open literature suggest that the energy released by the ultrasound during the cavitation phenomena can be used to enhance mass transfer (substrate/enzyme), hence increasing the rate of products formation, and also contributing to enhance the enzyme catalytic activity. Furthermore, the ultrasound is considered a "green" technology due to its high efficiency, low instrumental requirement and significant reduction of the processing time in comparison to other techniques. The main goal of this review was to summarize studies available to date regarding the application of ultrasound in enzyme-catalyzed esterification, hydrolysis, glycerolysis and transesterification reactions.

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This work reports new results about the solvent-free enzymatic production of ethylene glycol monostearate, an industrially important emollient ester conventionally produced by a chemical route. For this purpose, reactions were carried out using two commercial immobilized lipases, evaluating the effect of temperature, agitation, and enzyme concentration on the reaction conversion. It was shown that, for most tested conditions, reaction conversions around 100% were achieved. The reuse of the enzyme was also evaluated with satisfactory results up to four enzyme cycles. System scale-up by 9-fold allowed reaching conversions of up to 99%. Chemical analyzes showed that the product obtained through enzymatic synthesis presented very good characteristics, which makes the enzymatic esterification process employed in this work an interesting and promising route for possible application at industrial scale.

The feedstock cost can comprise more than 75% of the overall biodiesel cost, and then economic issues are the main limitations of biodiesel production. This research focused on the use of alternative feedstock and production processes. The production of fatty acid esters from residues becomes an interesting alternative route since it is possible to reduce the cost of the process. The present work aimed to produce methyl esters from the residual oil of the poultry industry, using a commercial soluble lipase Eversa Transform 2.0® (NS-40116). The effects of methanol (1.2 to 1.8 eqv), water (1 to 2 wt%) and enzyme (0.1 to 0.5 wt%) contents on reaction conversion were evaluated through a 2³ experimental design with three central points, at 45 ºC, 250 rpm for 16 and 24 h of reaction time. From the results, by using 0.3 wt% enzyme, 1.5 wt% water, and 1.5 eqv of methanol it was possible to reach the most effective esters conversion (90.61%).