[Isolation, identification and fermentation optimization of lactic acid bacteria for aquaculture water purification]

In order to get excellent strains for aquiculture water purification, we screened lactic acid bacteria from the aquaculture environment and intestinal tract of shrimp.

The potential water purification ability of lactic acid bacteria at normal and low temperature was evaluated in the simulated wastewater. Morphological physio-biochemical characteristics, 16S rRNA gene sequence analysis were used to identify strain r13. Single factor test and orthogonal-design experiment were applied to optimize fermentation for r13.

In total 136 lactic acid bacteria strains were isolated from 3 samples. The results of water purification test suggested r13 had higher removal ability of nitrite and ammonia from water. After 72 h treatment by r13, nitrite with 11.5 mg/L in the water was completely removed and ammonia degradation rate was 29.1% with 13.0 mg/L original concentration. According to morphological, physio-biochemical characteristics and 16S rRNA gene sequence analysis, r13 was identified as Lactobacillus plantarum. The optimal fermentation condition for r13 was 6.0 g/L yeast extract, 20.0 g/L glucose, 4.0 g/L sodium acetate, 2.0 g/L diammonium hydrogen citrate, 2.0 g/L monopotassium phosphate, 50 mL tomato juice, with inoculation rate 5% (V/V), at pH 6.0 and 34℃. Under this condition cultured for 72 h, the bacterial biomass reached 28.4 g/L wet weight and cell counting reached 4.4×109 CFU/mL.

Considering high nitrite removal ability, we suggested that r13 would be promising microorganism for water purification in aquiculture.