[Identification and characterization of Aspergillus aculeatus JMUdb058 for naringinase production].

OBJECTIVE

A new naringinase-producing strain, JMUdb058 was identified and characterized.

METHODS

The strain was identified by morphological observation and 28S rDNA homogeneous analysis. Naringinase was identified by monitoring the hydrolysis of naringin to prunin and naringenin using a reversed phase High Performance Liquid Chromatography (HPLC). The regulation of naringinase expression was studied by measuring naringinase activity of 11 different carbon sources and 7 nitrogen sources in shaking cultivation. The naringinase-producing capacity was investigated in both solid-state fermentation and submerged fermentation.

RESULTS

The macro-morphology and micro-morphology of JMUdb058 corresponded to the characteristics of Aspergillus section Nigri Gams, and the 28S rDNA sequences showed homogeneity at 100% to Aspergillus aculeatus. Crude enzymes prepared by both submerged fermentation and solid-state fermentation could hydrolyze naringin to prunin and naringenin. In addition, the enzyme could remove naringin from citrus juice effectively. Carbon resources, including hesperidin, naringin, rutin and rhamnose, and organic nitrogen resources, i. e., tryptone, soybean meal, yeast extract and corn syrup were shown to express the naringinase. The strain had an outstanding ability to yield naringinase in the solid-state fermentation, which showed an alpha-L-rhamnosidase activity of 5903 U/gds by HPLC, and the naringinase of 1939U/gds by HPLC and 72232 U/gds by Davis method.

CONCLUSIONS

It is the first time to report a stain of Aspergillus aculeatus can produce naringinase, carbon source containing rhamnose groups are able to induce the enzyme expression. The stain JMUdb058 is a new microorganism source for high yield of naringinase, in particularly by the solid-state fermentation.