Problem statement: Application of biocontrol agents to the field in pre-existing free-cell forms often results in poor cell viability which subsequently affects their efficacy in suppressing pathogen development. There is therefore a need to bioformulate these biocontrol agents not just to enhance their field potential, but for easy storage, delivery and application as well. Approach: In this study, the bioformulations for a biocontrol bacterium Serratia marcescens, was developed using bentonite clay as carrier material with various combinations of enrichment and additive materials. The most suitable bioformulation was determined by assessing the compatibility of the formulative materials in preserving cell viability during storage, the resulting appearance of the bioformulation, the protection confered to cells upon sunlight exposure and the efficacy of the formulated cells (with and without sunlight exposure) in inhibiting the growth of the pathogenic Fusarium oxysporum F. sp. cubense race 4 (FocR4). Results: Bioformulation benefited the cells when exposed to sunlight (UV rays). The benefits of bioformulation were attributed to the carrier material (bentonite clay) and the enhancement materials (NFSM and sucrose). They confer UV-protectant effects as well as providing nutrient source for the formulated cells. The additive material PABA was observed to have antimicrobial effect on the formulated cells. Formulative materials however has no impact on the efficacy of the cells in inhibiting FocR4 as no significant differences in percentages of FocR4 inhibition were observed between bioformulations with and without exposure to sunlight. Conclusion: Present study observed that incorporation of sucrose into Bentonite (BS) has the most potential for large-scale testing as it showed good viability and efficacy results.
Problem statement: Application of free-cell forms is usually impractical to achieve satisfactory bioremediative effect because the microbes are encumbered by the biotic and abiotic stresses from the environment. Approach: In this study, a hydrocarbon-degrading bacterium (Pseudomonas isolate UTAR EPA2) was formulated with various combinations of formulative materials, comprising of clay-based carrier materials such as Bentonite (B) and Kaolin (K), enrichment materials such as Non-fat skimmed milk (N) and Sucrose (S) and a UV-protectant agent Para-aminobenzoic acid (P). Formulated cells were treated to sunlight exposure for 6 h to mimic the conditions in the environment prior to testing for their efficacy in degrading petrol, a mixed hydrocarbon substrate. Results: Cells in all formulations including free-cell suspension were able to degrade petrol with a relatively high degradation efficacy of more than 66% even after exposure to sunlight. Degradation efficacy was slightly higher for kaolin-based formulated cells compared to bentonite-based formulations, especially after exposure to sunlight, although their percentages of degradation were not statistically different. Nevertheless, kaolin-based formulations have very low viable cell count especially in formulations with P (KP, KNP, KSP, KNSP). This suggested that aside from viable cells, the physical properties of the clays could have also contributed to the degradation of petrol. Conclusion: For storage purposes and applications in the field, we suggest that the bacterium is formulated with bentonite-based formulations especially using Bentonite (B) clay singly, as relatively high percentage of petrol degradation and viable cell count was achieved with this formulation
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