Lactibacillus casei is a Gram positive, rod shaped bacteria which is also anaerobic, non-sporing and non-motile. Lactobacillus casei is an acid tolerant bacteria, this means that it can survive in harsh environments. It can survive these harsh conditions as it is resistant to both gastric acid and bile. It is a faculative anaerobe which means that is can grow in both aerobic and anaerobic conditions although it develops much faster in the presence of oxygen, it is also a organotroph and its metabolism is homofermentive. It is found naturally in the intestinal tracts of animals and in fermented dairy products, although it is naturally found in the mouth and intestines of humans. Lactobacillus casei has both a wide temperature and pH range. In addition Lactobacillus casei is a mesophile which means its optimum pH is around 5.5 while its optimum temperature is around 30 to 40 degrees celsius. A Lactobacillus casei cell size is around 0.7- 1.1 x 2.0- 4.0 micrometers. Lactobacillus casei obtains most of its energy through converting glucose to lactic acid.