This study assessed the utilization of viscosity and zeta potential as a novel method to evaluate suspendibility of formulation of Sinorhizobium meliloti grown in starch industry wastewater for use as bio-inoculants. For this objective, sorbitol was used as a suspending agent at concentrations of 0 to 10% w/v. Model, based on multiple linear regression (with pH as dependant variable, and zeta potential, average particle size and sorbitol concentration as independent variables) demonstrated an important relation which was significant (p < 0.001, R(2) = 0.98). Sigmoid regression revealed a significant relation between zeta potential and suspendibility with p value = 0.007 and R-squared = 0.86, and between viscosity and suspendibility (p value < 0.0001 and R squared = 0.9823). Thus, these direct correlations established the lowering of measurement time from 12 h to 5 min. (C) 2011 Elsevier Ltd. All rights reserved.