Effect of pulsed electric field on spore germination rate and enzyme activity of Aspergillus niger

Abstract

Pulsed electric field (PEF) treatment on Aspergillus niger, which is an important source of several enzymes, was conducted to investigate the effects of different PEF parameters on spore germination of A. niger and the production of lipase and glucoamylase. The results showed that the spore germination rate and the relative activities of lipase and glucoamylase could be promoted when the electric field strength was in the range of 5– 15 kV/cm and the treatment time was in the range of 1– 7.5 ms. During the processing, the concentration of spores was maintained within a range of approximately 3.5 × 106 CFU/mL. Maximum increase of spore germination rate, lipase and glucoamylase activities were 217%, 25.6% and 31.3% respectively, which were observed when the spore suspension was subjected to PEF treatment with 10 kV/cm field strength for 5 ms. Lipase activity was inhibited with the increase of field strength and treatment time. Further analysis of the input energy density during PEF showed that the spore germination rate and the relative activities of enzymes were also promoted and then inhibited with increasing input energy density, but the electric field strength was more decisive. Industrial relevancePEF is an emerging non-thermal microbial treatment technology with the characteristics of short treatment time and low energy consumption. Aspergillus niger is an important microbial species in the food industry, as the enzymes it produces play an important role in various fields. This study applied PEF technology to A. niger and significantly promoted the germination of its spores, and the activity of its lipase and glucoamylase, which suggests PEF technology has the potential to be used to shorten the industrial production cycle of A. niger and its enzyme products.