Glycerin-Betaine-Based Natural Eutectic Solvent Enhanced the Spray Drying Resistance of Lactobacillus

Spray drying is a promising technique for embedding and stabilizing lactic acid bacteria. However, bacteria are unable to withstand high-temperature environment. Naturally small molecules fall short in meeting the evolving demands of production. Therefore, it is imperative to explore non-chemical pretreatment methods urgently, with the aim of enhancing their protective efficacy. In this study, natural deep eutectic solvents (NADES) were synthesized by glycerin-betaine to improve the survival rates of spray-dried Lactobacillus bulgaricus sp1.1. Results revealed that the spray drying survival rate of L. bulgaricus sp1.1 after adding NADES was 30.54%, which was 4.72 times higher than adding equal amounts of untreated glycerin and betaine, and the number of viable bacteria decreased less than 1 log after 6 months of storage. The investigation revealed that the impact of NADES was localized external to the cell rather than within. Through crosslinking with the peptidoglycan on the cell wall, NADES bolstered the cell wall structure thereby creating a protective barrier. This resulted in a reduction of damage to the membrane and ribosome induced by high temperatures during the lactic acid bacteria’s exposure. This study synthesized NADES using current protective agents as an effective method to enhance heat resistance of lactic acid bacteria for spray drying for the first time, and the lactic acid bacteria powder with high survival rate and high storage stability was successfully prepared, which provides a new approach for its industrial application. Graphical Abstract