Lipase production by Aspergillus ibericus using oil cakes and its application in esterification reactions

Abstract

Agro-industrial residues are a good nutrient source which may be applied in biotechnological processes. The aim of this work was to optimize lipase production using Aspergillus ibericus MUM 03.49 in different oil cakes (OC) produced in Brazil, by solid-state fermentation (SSF) process; and to apply produced lipase in esterification reactions for aroma esters production. SSFs were performed in 250 mL Erlenmeyer´s flasks containing 15 g of OC. After lipase extraction, lipase activity was determined by spectrophotometric method, using p-nitrophenyl butyrate as substrate. Esterification reactions were performed in falcon tubes with 5 mL volume reaction. Conversion yield was determined by the titration of the residual acid content, using 0.1 M NaOH. Highest lipase production of 127 ± 17 U/g was obtained using palm kernel oil cake (PKOC) and the combination of PKOC with sesame oil cake (SOC) improved lipase production to 328 ± 6 U/g. Optimization process led to 460 ± 38 U/g of lipase, after 6 days of fermentation, at a ratio of 1:1.2 PKOC:SOC, at 57% moisture content (MC) and 1% (w/w) NH4Cl. The obtained lipase was used in esterification reactions, in a solvent-free system. Maximum conversion yield (100%) to aroma ester was observed using decanoic acid with butanol and 5% (w/v) of biocatalyst at pH 7 or 8, at 200 rpm and 37 ºC for 24 h. SSF of mixture of PKOC and SOC by A. ibericus is an interesting strategy that allows considerable amounts of lipase production that can be used in aroma esters production.