Abstract
BackgroundA 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 methodsThe 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.ResultsThe 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.ConclusionsIt 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.
Highlights
A new prototype of bio-conditioner useful in rehabilitation of degraded soils was performed
Regarding the formulation, the most suitable combination to conserve the viability of strain Microbacterium sp. CSB3 (CSB3) was low-rank coal (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
When doing the multiple response analysis, which seeks to obtain an optimal joint response for both variables, optimal agitation was 232 rpm, while the pH was 7.5 (Table 5, Fig. 3). This result can be explained by the dynamics observed in the graphs of main effect for both variables; for biomass production the optimum value was the lowest level (6.5), the curve that defines pH behavior in the experiment is observed on an almost linear basis (Fig. 4), which indicates a non-significative difference between pH values; regarding to the yield, the main effect chart shows that the optimum pH for obtaining the maximum possible yield was 7.5 (Fig. 5)
Summary
A new prototype of bio-conditioner useful in rehabilitation of degraded soils was performed. Some research works have provided evidence of the ability of some bacteria to solubilize such coals and release humic substances during the process [1]. It has been observed that the direct application of these coals, inoculated with coal-solubilizing bacteria, has a positive effect on the edaphic properties of postmining soils [2]. Such background places the possibility of developing useful bioproducts within a rational context in the rehabilitation of degraded soils from the interaction of these bacteria and low-rank coals. Agric. (2020) 7:3 each microbial species has specific requirements, which must be determined if future modeling and scaling processes are to be considered [3]
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