Effects of a combination of lipases immobilised on desilicated and thiol-modified ZSM-5 for the synthesis of ethyl esters from macauba pulp oil in a solvent-free system

[Display omitted] •Covalent immobilisation of non-regiospecific and sn-1,3-specific lipases on mesoporous ZSM-5 was performed.•The biocatalysts were applied in reactions to produce fatty acid ethyl esters from a high acid raw material.•The combination of biocatalysts provided the best yields of fatty acid ethyl esters.•The influence of reaction parameters and of different acidity indexes were evaluated.•Repeated-batch processes showed more than 60% of their initial activity after six cycles. Lipases from Thermomyces lanuginosus (TLL) and Burkholderia cepacia (BCL) were immobilised on desilicated and thiol-modified ZSM-5 via covalent binding. These biocatalysts were tested, both alone and combined, in a reaction for the production of fatty acid ethyl esters from macauba pulp oil. A higher yield of esters was obtained with TLL combined with BCL, and the synergic effect was investigated systematically. Under the best conditions for the reaction, using a mixture of lipases (1% water content, 3:1 M ratio of ethanol to oil, at 30°C), the yield of ethyl esters was 93.1% ± 1.4% over48 h. The mixed lipases could be used in six operation cycles with a retained relative activity of higher than 60%. The combined biocatalysts were also evaluated using reactions carried out with macauba pulp oils with lower free fatty acid content, resulting in lower yields than those obtained with the initial oil.