Preparation of liquid bacterial fertilizer of phosphate-solubilizing bacteria from food waste-recycling wastewater

The feasibility of using food waste-recycling wastewater as fermentation substrate for producing liquid phosphate-solubilizing bacillus megaterium fertilizer was investigated. The results showed that bacillus megaterium cultured in the food waste-recycling wastewater reached logarithmic growth stage in as short as 3~4 days of adaptation period, and the number of strains reached the maxima on the 6~7th day. The wastewater II generated from hydrothermal pre-treatment was more suitable to be the fermentation substrate than wastewater I. The strain numbers cultured in wastewater II was 5times of what was cultured in wastewater I (4.8×1015 CFU/mL). Salt concentration in the wastewater had great influence on the growth and metabolism of Bacillus megaterium: the strain numbers first increased and then steeply decreased with the increase of NaCl concentration, indicating that the optimal NaCl concentration for bacterial culture was 10 g/L. The variation of pH and temperature affected the growth of bacillus megaterium significantly, while shaking speed and strain inoculation volume were not key influencing factors. The optimal culture conditions were pH 8, T=35℃, shaking speed 80r/min, and inoculums of 2% (V/V) as determined by orthogonal experiment. Phosphatesolubilizing fertilizer prepared by food waste-recycling wastewater was able to achieve effective phosphating of immobilized phosphorus: the dry weight of soy beans grown in soils amended with 0.025‰~2.5‰ of phosphatesolubilizing fertilizer was 70.7%~84.5% of that grown in the soil amended with 5% of inorganic fertilizer on weight basis. Moreover, the optimal amended ratio of the microbial fertilizer was 0.25‰. © 2016, Editorial Board of China Environmental Science. All right reserved.