Design of a bio-conditioner prototype for the treatment of degraded soils: biomass production and lignite formulation for Microbacterium sp. CSB3

Abstract Background A new prototype of bio-conditioner useful in rehabilitation of degraded soils was performed. In order to obtain this aim two stages were established: production of biomass of Microbacterium sp. CSB3 and formulation of this inoculum in a sediment supplemented with low-rank coal (LRC). Materials and methods The effect of agitation and pH on microbial growth was determined. As response variables, the final production of biomass (Xf) and yield (Yx/s) were determined. Growth dynamics of CSB3 in a 2-L reactor was also evaluated through Xf, Yx/s and the determination of kinetic parameters (specific growth rate [μ] and duplication time [Dt]). The formulation of CSB3 was evaluated; mixtures of several LRC proportions with a sediment from a municipal aqueduct were made. During 90 days, the viability of CSB3 was monitored by counting CFU. Results The optimal pH and agitation for Xf and Yx/x were 7.5 and 232 rpm, respectively; the values of Xf, Yx/s, μ and Dt in 2-L reactor were: 1.5 gL−1, 0.28 g/g, 0.0208 h−1, 33.3 h, respectively. Regarding the formulation, the most suitable combination to conserve the viability of CSB3 was LRC 25%–sediment 75%; the heavy metals content of LRC allow to infer that the prototype of bio-conditioner does not represent a pollution risk for environment soil. Conclusions It was possible to optimize the growth of CSB3 under laboratory conditions. The viability of CSB3 could be maintained by a formulation in a sediment supplemented with lignite; this formulation constitutes a new prototype of soil bio-conditioner.