In situ Transesterification of Crambe Seeds with Dimethyl Carbonate Using an Enzymatic Catalyst

Abstract

In situ transesterification of crambe seeds oil was investigated to produce fatty acid methyl esters using dimethyl carbonate as acyl acceptor and lipase Novozyme 435® as the catalyst. First, the effects of solvent-to-seeds ratio, seed pretreatment, and extraction time were evaluated on the seed oil removal, comparing the results with conventional Soxhlet extraction. Then, the effects of enzyme loading (5 to 30 wt.% based on the oil mass) and reaction time (60 to 540 min) were evaluated on the simultaneous extraction and reaction. The highest oil extraction yield (ca. 26 wt.%) was achieved at the solvent-to-seeds ratio of 6 mL g-1 and 360 min. The oil obtained from seeds that received thermal pretreatment showed a higher concentration of minor compounds. The highest ester content (76.71 wt.%) was obtained with an enzyme loading of 20 wt.%, solvent-to-seeds ratio of 6 mL g-1, for 480 min. The reaction samples showed a predominance of erucate and oleate esters, with identification of the co-products formation (glycerol carbonate and glycerol dicarbonate), and ca. 5 wt.% of acylglycerols.