Trehalose is a non-reducing disaccharide widely present in organisms. It has unique biological characteristics and plays an important role in protecting cells and biomolecules in many fields such as medicine, agriculture and food. In recent years, as an important microorganism in the food fermentation industry, lactic acid bacteria (LAB) have gradually become a research hotspot. In order to drive further research on the protective mechanism of trehalose on LAB, this article reviews recent studies on the protective mechanism of trehalose on biomolecules and its application in protecting LAB from environmental stress. Four hypotheses explaining the protection mechanism of trehalose on biomolecules have been proposed: water substitution, glass state, priority exclusion and intermolecular synergism. Trehalose can protect LAB from harsh environments such as dehydration stress, high temperature stress, freezing stress and oxidative stress. This article will provide a theoretical basis for applying trehalose as a protective agent to improve the resistance of LAB to adverse environments.

Lactic acid bacteria (LAB) are an important group of microorganisms used in the fermented food industry. Lactic acid and special flavor substances produced by the metabolism of LAB can impart fermented foods with unique qualities, and LAB have been widely used in the food industry, health care and clinical medicine. Therefore, the preparation and storage of LAB starter cultures are crucial. As the traditional method for producing dried agents, freeze-drying technology has the disadvantages of high cost, long time consumption and high energy consumption. In contrast, spray drying has the advantages of low cost, high efficiency and rapidity, and continuous production. It is a potential alternative to freeze-drying for the production of LAB powder. However, hot air generated during spray drying kills LAB, resulting in a low survival rate after drying. This paper reviews the current status of research on different spray drying process parameters, and it highlights the external and internal factors that may affect the quality and efficacy of spray-dried LAB starter cultures.