Characterization of Antagonist Potential of Selected Compost Bacterial Isolates (CBI) against Plant and Human Pathogens

Abstract

Several fecal and enteric pathogens are present within the primary organic raw materials that are introduced to compost piles. These pathogens may compete with the existing microbiota and limit their efficiency, yielding only partial decomposition of the final compost. These pathogens also affect the process kinetics and persist in the final compost or may even regrow as a result of the declining effect of indigenous antagonistic micro-organisms. In this work, 11 indigenous bacterial isolates were selected from compost piles that were constructed from different percentages of comingled primary organic raw materials. Enzymatic, biochemical, and genetic characterization profiling of these strains was fulfilled. The top hits supplied by GenBank proved the genetic diversity of these strains, which belonged to 6 different families. This diversity, applied also at enzymatic and biochemical levels, showed the different degradation patterns of amino acids, carbohydrates, hormones, and proteins. CBI2 has been shown to be the most active isolate in the degradation of the different types of hormones and proteins from dairy products but lacks the enzymes needed for the degradation of ammonia into nitrogen. The antagonistic potential of recuperated secondary metabolites proved the total inhibition of all strains against Fusarium oxysporum and no growth limitation against Botrytis cinerea. Only the secondary metabolites of CBI1, CBI5, and CBI9 isolates showed inhibitory activity against Salmonella Typhimurium and Escherichia coli, whereas only those of CBI6 and CBI8 inhibited the growth of Salmonella Typhimurium and Listeria monocytogenes accordingly. From that finding, these strains are considered pioneering, with high potential to ensure both the efficient degradation of organic matter and the elimination of existing pathogens when applied to compost piles.

Study of Raw Material Pretreatment and the Microbiota Selection Effect on the Composting Process Efficiency

“…In most cases, these microbiota are not active in the decomposing process, and/or have low antagonistic potential regarding their secondary metabolites. Thus, they are subjected to severe competition by existing pathogens such as Listeria monocytogenes and Salmonella Typhimurium [36]. For this, the selection and application of an abundant number of adapted microorganisms, especially Actinobacteria and fungus, existing naturally in the environment, which can be easily invested and used in the pretreatment of biomass, targeting cellulose and hemicelluloses [37], helps to fasten the process.…”

“…In previous work [36], eleven bacterial isolates, including three different strains of Bacillus subtilis (CBI 1, CBI 2, and CBI 7), two different strains of Providencia sp. (CBI 3 and CBI 11), Alcaligens sp.…”

Aerobic and Anaerobic Digestion of Agro-Industrial and Livestock Wastes: A Green and Sustainable Way toward the Future

“…The higher the number of microbes, the higher is the rate of decomposition. The secondary metabolites produced by the microbes in the inoculum suppresses the growth of other microbes and in turn results in composts with high nutritive value [8]. It is suggested that, humification of lignin waste which is present in excess will increase the concentrations of ligninase, protease, xylanase and urease.…”

“…Solid waste management has become a major issue in several developing countries in recent times [8]. Nutrient retrieval from organic wastes such as kitchen litter, agro-waste, and municipal waste is crucial for waste management and environmental fortification.…”