[Isolation, screening and identification of yeast for aquaculture water purification]

In order to get excellent yeast strains for aquiculture water purification, we isolated, screened and identified yeasts from the aquacultural environment and intestinal tract of shrimp.

The potential water purification ability of yeasts, isolated from the activated sludge of aquacultural environment and intestinal tract of white shrimp and mantis shrimp under normal and low temperature, was evaluated in the simulated wastewater. Morphological physio-biochemical characteristics, 5.8S rDNA ITS gene sequence analysis were used to identify the strains.

Thirty-seven yeast strains were isolated from 3 samples, among them 16 strains were isolated under normal temperature (25 °C) while 21 strains were isolated under low temperature (15° C). Water purification test suggested 5 strains isolated under 25 °C and 6 strains isolated under 15 °C had higher removal ability of nitrite and ammonia from water. After 48 hours treatment with DN9 and CN6, 10.64 mg/L nitrite in the water was completely removed. After 96 hours treatment, CODcr degradation rates of the 2 strains were 52% and 67%, respectively. According to morphological, physio-biochemical characteristics and 5.8S rDNA ITS gene sequence analysis, the strain DN9 was identified as Rhodotorula mucilaginosa and CN6 as Rhodosporidium paludigenum.

Strains DN9 and CN6 would be promising for water purification in aquiculture.