Improving ureolysis in human urine by inoculating Amphibacillus bacteria selected by enrichment cultures

Reclaiming nitrogen through urine-recycling technologies is increasing. Ureolysis serves as the foundation for this shift as it decreases the energy demand for nitrogen fertilizer production. However, this process has been understudied because of its low efficiency and spontaneous nature. This research shows that using an external inoculum can increase efficiency by 3.5 times. For the selection of the inoculum, the technique of enrichment cultures in Christensen medium was used, which resulted in increased activity and reproducibility of selected cow dung bacteria (CDG). The kinetic parameters V_max and K_m increased from 375.62 ± 14.96-560.67 ± 88.89 mmol NH⁺₄ · kg^-1 min^-1 and from 115.57 ± 0.08-220.35 ± 53.29 mM, respectively, improving ureolysis rate and microorganism acclimatation. Specific inocula are crucial for improving ureolytic activity and discovering new findings. The bacterial community in the enrichment cultures was analyzed by DGGE and sequencing of 16S rRNA genes. The bacteria responsible for ureolysis was related to Amphibacillus genus. For the first time, the viability of the Amphibacillus has been demonstrated to carry out ureolysis in human urine for sustainable nutrient recovery.