Abstract
Three commercial lipases, Lipomod 34MDP (free lipase from Candida rugosa), Lipozyme RM IM (immobilized lipase from Rhizomucor miehei) and Novozym 435 (immobilized lipase B from Candida antarctica) were evaluated as catalysts in the production of biolubricant base oils. This was accomplished via the esterification of free fatty acids obtained from soybean-oil hydrolysis and different polyols (neopentyl glycol, NPG; trimethylolpropane, TMP; and pentaerythritol, PE). Reactions carried out with free C. rugosa lipase showed the highest conversions for the three polyols (97% for NPG, 100% for TMP and 55% for PE) after 24 h, while Novozym 435 and Lipozyme RM IM resulted, respectively, in 65% and 92% for NPG, 15% and 39% for TMP and 1% and 0% for PE. Then, Accurel MP1000 (a microporous polypropylene support, PP) was used to immobilize the C. rugosa lipase; enzyme loading used was 0.3 mg/g. The zymography analysis showed that the protein band of 60 KDa present in the C. rugosa lipase extract was the main protein responsible for the extract activity in the biolubricant synthesis and it was successfully immobilized onto the support. The immobilized lipase (34MDP-PP) showed conversions of 99% for NPG and 92% for TMP, after 24 h of reaction, maintaining the results obtained with the free enzyme. The 34MDP-PP could be reused for six consecutive reaction cycles without a reduction in the final conversion, using NPG and TMP as substrates. Using Lipozyme RM IM, the conversion decreased from 92 to 56% after six consecutive reactions. The soybean esters of NPG and TMP showed good viscosity indexes, higher than 200.