Lipase production by Aspergillus brasiliensis in solid-state cultivation of malt bagasse in different bioreactors configurations

Abstract

We evaluated the conditions to produce lipase in solid-state cultivation using a recently isolated strain of Aspergillus brasiliensis 157f in bioreactors of different configurations: static flat-bed, plugged-flow bed with forced water-saturated aeration, and pilot-scale rotating drum bioreactor, using malt bagasse as substrate. Lipase production was optimized applying experimental design analysis, which showed optima parameters defined as pH 7.7, addition of 11.3 % of soybean oil to the medium, and culture temperature of 32.7 ^oC, in static flat-bed. The highest enzyme activity (9.8 U.g^-1 substrate) was obtained in the plugged-flow bed with forced water-saturated aeration. The fermented culture medium was lyophilized to create a solid enzymatic preparation (SEP), which was used to test the possibility of using this cheap biocatalyst in bioreactors to mediate esterification and transesterification reactions. SEP presented lipase activities of 7.35 U.g^-1 substrate, indicating the possibility of further enhancing aspects of the use of such biocatalyst.

Key words
Aspergillus brasiliensis; brewery’s spent malt; lipase production; Solid-state cultivation; transesterification reaction