Indonesian Journal of Biology Education Vol. 4, No. 1, 2021, pp: 25-30 pISSN: 2654-5950, eISSN: 2654-9190 Email: ijobe@untidar.ac.id Website: jurnal.untidar.ac.id/index.php/ijobe 10.31002/ijobe.v4i1.4027 Indonesian Journal of Biology Education Vol. 4, No. 1, 2021 | 25 The Benefit and The Content of Lactic Acid Bacteria “Lactobacillus casei Shirota Strain” in Yakult Tri Ujilestari 1* , Dian Fajarwati Susilaningrum 2 , Bernita Adelia Damayanti 3 Maulina Afni Saputri 4 , Rizal Nur Alfian 5 1 Biology Education Study Program, Universitas Tidar, Indonesia 1 Biology Education Study Program, Universitas Tidar, Indonesia 1 Biology Education Study Program, Universitas Tidar, Indonesia 1 Biology Education Study Program, Universitas Tidar, Indonesia 1 Biology Education Study Program, Universitas Tidar, Indonesia Email: 1 triujilestari93@gmail.com, 2 dianfajarwatisusilaningrum@gmail.com, 3 adeliajogin@gmail.com, 4 maulinasaputri754@gmail.com, 5 rizalnuralfian2312@gmail.com. *Corresponding Author Article History Abstract Received : 05-03-2021 Revised : 23-03-2021 Accepted : 30-04-2021 The purpose of this article is to determine the content of lactic acid bacteria in a probiotic beverage (Yakult) with a starter fermentation of Lactobacillus casei Shirota strain and to find out its benefits for digestion. In this study, the library research method was used by obtaining data and materials from journals. The author tries to describe the content of lactic acid bacteria “L. casei Shirota strain” in Yakult and its benefits for the digestive system. The results showed that the levels of L. casei Shirota strain in fermented milk were 1.27-1.70% with an average of 1.42%. In the Indonesian National Standard 01-2891-2009, the lactic acid bacteria content of L. casei Shirota in fermented milk was 0.5-2.0%. L. casei Shirota can produce lactic acid and acetic acid, so that, it can decrease intestinal pH and prevent pathogens bacteria’s growth. Probiotic beverage from fermented milk using L. casei is beneficial for consumption for its ability in inhibiting the growth and development of pathogenic bacteria in the gastrointestinal tract, help the absorption of vitamins and antioxidants, eliminate toxic components contained in food, as well as producing several vitamins through the synthesis of digestive enzymes. Keywords: Lactic Acid Bacteria, Lactobacillus casei, Probiotics Beverage, Yakult Article link ©the authors This is an open-access article under the CC-BY-NC-SA license https://creativecommons.org/licenses/by-nc-sa/4.0/ Introduction Microorganisms are commonly found everywhere, such as: in the soil, aquatic environments, and atmospheres (Pelczlar and Chan, 2008). Microorganisms have a role as producers, consumers, and reducers (Utomo, 2012). The microorganisms were dividided into two groups unicellular and multicellular. Microorganisms have the characteristics of plant cells, animal cells, and both. The main character of microorganisms can differentiate based on their cellular material compositions (Pelczlar and Chan, 2008). Bacterias are one of the groups of prokaryotic microorganisms (single-celled). That life is colonized and does not have a core-sheath but can live anywhere (Jawetz et al., 1996). Bacteria are the most numerous organisms compared to other living things. Some bacteria can be beneficial or harmful. That can cause disease/harm in humans are called pathogens, while beneficial bacteria in humans are called probiotics. One example of beneficial bacteria in humans is lactic acid bacteria (Khanifah, 2012). Lactic acid bacteria (LAB) are cocus and stems, gram-positive bacteria, aerobic to anaerobic. LAB does not have spores and cytochromes. LAB has required complex nutrients such as amino acids, vitamin