Isolation, identification and fermentation optimization of a thermophilic sulfide-oxidizing strain Paenibacillus ehimensis

Abstract:

[Background] The sulfur-containing odor emitted from municipal sludge composting could not only pollute the surrounding environment but also reduce the compost qualities. Biological desulfurization technology is highly efficient and without secondary pollutions. However, recent studies have been focused on the mesophilic strains, which are usually inactivated in thermophilic composting environments. Studies on the thermotolerant sulfide-oxidizing bacteria are scarce, and the desulfurization performance of the thermotolerant bacteria awaits further study. [Objective] To provide a theoretical basis for the biological application of composting desulfurization, a thermotolerant sulfide-oxidizing strain was isolated and identified, and the environmental conditions of the sulfide oxidation process were optimized. [Methods] The selective medium containing sulfide was used to screen and purify the thermophilic strain from sludge compost materials. The strain was identified by its morphological characteristics, physiological and biochemical analysis, and 16S rRNA gene sequence analysis. Single-factor and orthogonal experiments were used to optimize the fermentation conditions, and we also used the Logistic model to fit the growth kinetics curve of the strain. [Results] A thermophilic sulfide oxidizing strain LYH-1 was isolated and identified as Paenibacillus ehimensis; the GenBank accession number was MW659161. The optimized sulfide oxidation conditions were 50℃ of the temperature, pH 7.5, and 5% of the inoculation amount, the sulfate production amount reached 86.89 mg/L, and the production rate was 36.20%. The optimized growth conditions were 50℃ of the temperature, pH 8.0, and 5% of the inoculation amount, and the OD₄₂₀ reached 0.520; under these conditions, the growth kinetics were fitted to obtain the maximum specific growth rate at 0.304 2 h^-1. [Conclusion] Paenibacillus ehimensis LYH-1 has strong sulfide oxidation and environmental resistance abilities. It provides new bacterial resources for biological desulfurization and theoretical support for sulfur-containing odor control during the high-temperature period of sludge composting.