Abstract
Application of rhizobial inoculant is an agricultural practice successfully used to increase growth and yield of leguminous plants. Development of a concentrated culture is essential for advanced formulations. This study assessed the use of starch industry wastewater as a potent carbon source for production of Sinorhizobium meliloti, with a maximum cell count of 4×109 CFU/mL. Optimal conditions for maximum recovery of cells (>99%) during centrifugation were determined to be 8 000 g, at a temperature of 20 °C for 20 min, pH 7, using a swinging bucket rotor and a surface response methodology. Of the different centrifugal aids tested, starch (2% w/v) best minimized the loss of microbial cells during recovery from the supernatant. A fixed- angle-rotor experiment was also carried out to determine differences in recovery between centrifugal configurations; optimal recovery was observed with the swinging bucket rotor (>99%) versus a fixed angle rotor (90%). A further decrease (from 90% to 87%) in recovery was observed with a 20 times increase in broth volume at 8 000 g, centrifuged for 20 min at 20 °C. The addition of soya oil during centrifugation contributed to emulsion formulation. A slight decrease was observed in CFU values using an antimicrobial agent, as compared to the control of centrifugate and oil emulsified with 0.1% v/v surfactant, after one month of storage. Suspension formulation with alginate additive showed a cell viability of more than 10 9 CFU/mL after 9 weeks of storage. This study demonstrates the feasibility of cell recovery and simultaneous formulation development of Sinorhizobium. Further investigation of parameter optimization for development of advanced formulations using recovered cells is warranted.
Keywords
Get full access to this article
View all access options for this article.