Preservation of Kocuria rhizophila DSM 348 by spray drying using different protective agents for improvement of bacterial viability

Biotechnological and pharmaceutical processes based on bacteria require an inoculum with high long-term viability. In order to provide a stabilized bacterial culture for biodegradation of ammonia and ammonium, the model species Kocuria rhizophila DSM 348 was spray-dried using different protective agents. Providing a medium with 200 g/L skimmed milk powder (SMP) and 12.5 g/L monosodium L-glutamate (MSG) resulted in a survival rate of 99.1% ± 3.6% immediately after spray drying, whereas 200 g/L trehalose and 12.5 g/L MSG led to a lower viability (34.7% ± 5.9%). A reference medium with phosphates (7 g/L KH₂PO₄ + 7 g/L K₂HPO₄) accomplished a survival rate of 9.8% ± 2.9%. Long-term experiments confirmed high viability of spray-dried bacteria after 52 weeks at 4 °C with less than 1 log-reduction compared to the first day of storage, resulting in powders with at least 10¹⁰ CFU/g.