Lipase de Aspergillus niger foi imobilizada por deposição utilizando Celite e as atividades de hidrólise e esterificação, a estabilidade e a enantioseletividade das formas livre e imobilizada foram comparadas. Ambas as preparações mostraram propriedades bioquímicas similares, com atividade máxima em pH 6,0 e temperatura de 30-40 ºC. Não foram observadas diferenças na atividade hidrolítica em função do pH para as duas formas da enzima. Os efeitos mais importantes observados após a imobilização foram a estabilidade térmica e a melhoria da atividade de esterificação na reação do (R,S)-ibuprofeno com 1-propanol em presença do isooctano. Além disso, a lipase na forma imobilizada manteve, pelo menos, 73% de sua atividade de esterificação após 5 dias de armazenamento a 40 ºC e pôde ser reciclada e reutilizada por pelo menos 6 vezes.

Aspergillus niger lipase was immobilized by deposition on Celite and the hydrolytic and esterification activities, stability and enantioselectivity of both free and immobilized enzyme were compared. Both the free and immobilized preparations showed similar biochemical properties, with maximum activity at pH 6.0 and a temperature of 30-40 ºC. The most important effects observed when the lipase was immobilized were thermal stability and an improved esterification activity during the reaction of (R,S)-ibuprofen with 1-propanol in isooctane. Moreover, immobilized Aspergillus niger lipase maintained an esterification activity of at least 73% after 5 days of storage at 40 ºC and can be recycled and reused at least 6 times.

Microbial lipases have a great potential for commercial applications due to their stability, selectivity and broad substrate specificity because many non-natural acids, alcohols or amines can be used as the substrate. Three microbial lipases isolated from Brazilian soil samples (Aspergillus niger; Geotrichum candidum; Penicillium solitum) were compared in terms of their stability and as biocatalysts in the enantioselective esterification using racemic substrates in organic medium. The lipase from Aspergillus niger showed the highest activity (18.2 U/mL) and was highly thermostable, retaining 90% and 60% activity at 50 ºC and 60 ºC after 1 hour, respectively. In organic medium, this lipase provided the best results in terms of enantiomeric excess of the (S)-active acid (ee = 6.1%) and conversion value (c = 20%) in the esterification of (R,S)-ibuprofen with 1-propanol in isooctane. The esterification reaction of the racemic mixture of (R,S)-2-octanol with decanoic acid proceeded with high enantioselectivity when lipase from Aspergillus niger (E = 13.2) and commercial lipase from Candida antarctica (E = 20) were employed.