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Abstract: The lubricants of the future have to be more environmentally adapted, have a higher level of performance. Synthesis esters (SEs) which can be used as raw materials for biodegradable lubricant base oils are increasing in popularity due to superior technical properties. Direct esterification of trimethylolpropane (TMP) with fatty acid in a solvent free system, by immobilized lipase from Candida sp. 99–125 was studied. Investigations of important factors were carried out involving temperature, time, enzyme amount, substrates molar ratio and water content. For 2g caprylic acid, under the optimal conditions, with 0.4g immobilized lipase, at substrates molar ratio 1:10 (TMP to acid), temperature 40°C and water content controlled under 0.8% (w/w), the total conversion of fatty acid with TMP reached up to 96% and the formation of trisubstituted TMP esters reached 93%. Water content controlled during esterification process was found to be critical for high yield of direct esterification. [Copyright &y& Elsevier]

Highlights: [•] Lipase was absorbed on surface hydrophobic modified silk fibers. [•] Immobilized lipase and feeding methods improve synthesis of tri-TMP esters. [•] Immobilized lipas showed increase esterification activity and decrease hydrolysis activity. [•] TMP-feeding methods kept a high molar ratio of fatty acid to TMP during process. [Copyright &y& Elsevier]