Publication:

Production of L-asparaginase by Aspergillus niveus under solid-state fermentation using agroindustrial byproducts

Background L-asparaginase, produced mainly by microrganisms, cleaves L-asparagine to aspartic acid and ammonia as products. This enzyme has been applied in the treatment of the leukemia and in food preparation preventing the acrylamide formation.

Methods Aspergillus niveus was grown in different solid substrates (agroindustrial byproducts) moistened with different agents (tap water, distilled water and several salt solutions) for different periods (24-240 h) at 30ºC. The enzyme extract was obtained with the addition of cold distilled water, agitation at 50 rpm for 30 min and filtration. The filtrate was used to determine the L-asparaginase activity through the hydroximate aspartic methodology using L-asparagine as substrate. The influence of temperature (30-75ºC), pH (3-9) and chemical compounds on the enzyme activity was analyzed.

Results The highest level of enzyme production was obtained using the M1 mixture (wheat bran, crushed soybean, orange peel; 1:1:1, w/w/w) as substrate humidified with Czapeck Dox salt solution (1:0.5, m/v) for 48-120 h, at 30ºC. The best temperature and pH for the enzyme activity were 35ºC and 5.0, respectively. The enzyme activity was increased in the presence of NaCl and some organic solvents (acetonitrile, butanol ethanol, isopropanol and methanol).

Conclusions A. niveus produced L-asparaginase under SSF using a mixture of agroindustrial byproducts as solid substrate in the absence of L-asparagine as inducer. The temperature and pH of activity, as well as the NaCl tolerance, indicate its potential to be applied for different purposes. A. niveus can be an interesting source of L-asparaginase gene to be investigated targeting future application.