Development of emulsion from rhizobial fermented starch industry wastewater for application as Medicago sativa seed coat

摘要

Starch industry wastewater was efficiently employed for the production of Sinorhizobium meliloti and the concentrated culture was used for the development of a biofertilizer formulation. Tween-80 (0.02 g/L) acted as the best emulsifier for a Sinorhizobium–canola oil emulsion. The stability of the emulsion and survival of the organism was enhanced by supplementation of xanthan gum at pH 8. The refrigerated condition was most favorable for stability and survival of the microorganism. The survival of microorganism at 4±1 deg C was 2.78×1010 and 2.01×1010 CFU (colony forming unit)/mL on storage for 1 and 2 months, respectively. The values were higher than the prescribed cell count (×103 CFU/mL) for field application. At 40 deg C, the survival of bacteria reduced from 3×1010 CFU/mL to 8.1×109 and 8.8×106 CFU/mL in 1 and 2 months, respectively. Emulsion-coated seed was incubated at different temperatures and a cell count of 105 CFU/seed was observed after 2 months of storage at 4 deg C, which wasequal to the highest level of the described requirement (103–105 CFU/seed). Emulsion supplemented with xanthan gum improved the shelf-life under optimized conditions (Sinorhizobium concentrate – canola oil (1:1) emulsion with 0.02 g/L Tween-80; storage at pH 8 and temperature 4±1 deg C) and this emulsion with the required cell count and prolonged viability was used for the pre-inoculation of seed or for in situ soil application.