**1. Introduction**

Lactic acid bacteria (LAB) are significant microorganisms that primarily generate lactic acid as a byproduct of metabolic processes. In the agricultural, pharmaceutical, food, and medical industries, lactic acid bacteria serve a wide range of purposes. One of the most common methods of preserving and prolonging the shelf life of food is the use of LAB, which is used in many food fermentations [1]. Lactobacillus

is a gram-positive, rod-shaped bacteria commonly found in fermented foods that are beneficial for human health [2]. *L. bulgaricus* is among the most significant LAB, as it is recognized as one of the two bacteria needed for yogurt production. *L. bulgaricus* was isolated from Bulgarian yogurt, and today, the yogurt manufacturing industries use it in addition to *Streptococcus thermophilus* for fermentation*.* This LAB (*L. bulgaricus*) plays a significant role during yogurt production regarding organoleptic, hygienic, and perhaps probiotic characteristics; as a result, it is a safe probiotic with several advantageous qualities [1]. According to the FAO/WHO [3], probiotics are "live microorganisms which when administered in adequate amounts confer a health benefit on the host." These organisms are commonly found in foods such as yogurt, kefir, and sauerkraut, as well as in dietary supplements. Mani-López et al. [4] reported that the food sector, especially the dairy industry, is looking to enhance its knowledge of different probiotic bacteria to produce products that offer health benefits at a reasonable cost. However, the development of starter cultures for fermented dairy products depends on the microbial symbiosis of several lactic acid bacteria with excellent fermentation abilities [5]. Research confirms that commercial yogurt starter cultures' most significant fermentation properties include rapid acidification, specific flavor compounds, weak post-acidification, and health benefits with minimal dietary needs [1].

One of the key challenges in using Lactobacillus as a probiotic is ensuring its safe and effective delivery. Therefore, various delivery systems have been developed for Lactobacillus*,* and these delivery systems protect the bacteria from extreme conditions such as temperature, processing, storage, and the ability to withstand stomach acids and bile salts to colonize and exert their beneficial effects [6]. The success of a delivery system depends on several factors, including the viability of the bacteria during production and storage, and the ability of the delivery system to protect the bacteria during transit through the digestive system [6]. Advances in technology and research have led to the development of more effective delivery systems for Lactobacillus*,* which can potentially improve human health in various ways. Therefore, in this review, we discuss lactic acid bacteria focusing on Lactobacillus and their beneficial effects on human health applications as well as their effective delivery system to withstand harsh conditions such as temperature, processing, and storage, to maintain their viability.
