Production of a lipase activity by solid state fermentation using Aspergillus niger MYA 135: Impact of different humectant mixtures

Abstract

The solid state fermentation is an economical alternative for production of industrial enzymes such as lipases mainly because this technology proposes the reuse of agro-industrial waste as well as adding value to those residues. Lipases (EC 3.1.1.3) are triacylglycerol hydrolases that catalyze the hydrolysisof triglycerides to free fatty acids and glycerol. In non-conventional systems these enzymes can also catalyze esterification, transesterification and interesterification reactions. The aim of this work was to evaluate the production of a lipase activity from Aspergillus niger MYA 135 by solid state fermentation using different humectant mixtures. As solid substrate, washed sugarcane bagasse was used. Humidity was adjusted to 90 % with the following mixtures containing (in g/l): 1) M1: Vinasse 5.0, molasses 5.0, milk serum 10.0, peptone 5.0, cerelose 5.0, waste frying oil 10.0, FeCl3 1.0, CaCl2 0.5. 2) M2: Sucrose 10.0, KH2PO4 1.0, NH4NO3 2.0, MgSO4 0.2, CuSO4 0.06, FeCl3 1, olive oil 20. 3) M3: Sucrose 10.0, KH2PO4 1.0, NH4NO3 2.0, MgSO4 0.2, CuSO4 0.06, yeast extract 1.0, peptone 5.0, olive oil 20. Humectant mixtures M1 and M2 were previously used as culture media for A. niger MYA 135 lipase production by submerged fermentation. Humectant mixture M3 was formulated from literature data. Reactors were inoculated with 105 conidia per gram of solid substrate and incubated at 30°C during 48 h. Then, the fermented substrate was dried at 45 °C and used as enzyme source. The hydrolytic activity was measured with p-nitrophenyl palmitate (C16) as substrate. The molar extinction coefficientof p-nitrophenol (p-NP) under the given assay conditions was 0.0073 μM-1 cm-1. One unit of enzyme activity (U) was defined as the amount of biocatalyst that released 1 μmol of p-NP per minute. Specific activity was expressed as Unit per gram of dry fermented substrate (U/gdfs). All experiments were performedin triplicate and analyzed with the Minitab software for Windows. Under our assays conditions, the specific lipase activity obtained from sugarcane bagasse supplemented with M1, M2 and M3 were 626.7, 978.1 and 252.8 U/gdfs, respectively. In addition, the performance of the biocatalysts producedby submerged fermentation using the same liquid mixtures was also discussed.