Lactobacillus paracasei

Lactobacillus paracasei (commonly abbreviated as L. paracasei) is a gram-positive, facultatively heterofermentative species of lactic acid bacteria that are commonly used in dairy product fermentation and probiotics. L. paracasei is a bacterium that operates by commensalism. It is commonly found in many human habitats such as human intestinal tracts and mouths as well as sewages, silages, and previously mentioned dairy products. The name includes morphology, a rod-shaped (bacillus shape) bacterium with a width of 2.0 to 4.0μm and length of 0.8 to 1.0μm. So far, thirty four different strains of L. paracasei have been isolated from a variety of environments. Sixteen of those strains have been isolated from dairy, ten from plants, and eight from human and animal gastrointestinal tracts.L. paracasei is genotypically and phenotypically indistinguishable from other members of its genus such as Lactobacillus casei and Lactobacillus rhamnosus. However, they are easily differentiated from each other by their fermentation profiles. Its fermentative properties allows it to be used as biological food processors and supplements for diets and medical disorders, especially in the gastrointestinal tract. Although probiotics are considered safe, they may cause bacteria-host interactions and adverse health consequences. In certain cases there is a risk of bacteremia when probiotics are used. Currently, the probiotic strain, frequency, dose and duration of the probiotic therapies are not established. Lactobacillus paracasei is a gram-positive, facultatively heterofermentative, non-spore forming microorganism. The cells of L. paracasei are typically rod shaped, with a size range of 2.0μm to 4.0μm in width, and 0.8 to 1.0μm in length. The organism is nonmotile. L. Paracasei cells often have square ends, and may exist either in single form or in chains. L. paracasei grows optimally in a temperature range between 10 and 37 °C. No growth takes place above 40 °C. The organism is able to survive for approximately 40 seconds in a maximum temperature of 72 °C. As L. paracasei is facultatively heterofermentative: lactic acid is produced from most strains. L. paracasei exist as a common inhabitant of the human gastrointestinal tract as part of the normal flora. Naturally fermented vegetables, milk, and meat may also contain strains of L. paracasei. Lactobacillus paracasei belongs to kingdom Bacteria. L. paracasei is part of the division Firmicutes, and also belongs to the class Bacilli. The order and family are Lactobacillales and Lactobacillaceae respectively. The argument on the nomenclature of L. paracasei versus L. casei has been one of intense debate. Most of the species profiled as L. casei or L. paracasei have been found to be part of the same species. In 1989, it was proposed that L. paracasei be designated a subspecies (paracasei) to account for the species that it shares DNA homology with. It has been shown their names have been used interchangeably in scientific literature. 16S RNA sequence homology has confirmed the relatedness between these species. Historically, the difference between Lactobacillus paracasei and other lactobacilli has been based on biochemical characteristics. There is an approximately 90% sequence identity between casei, paracasei, and rhamnosus. However, there are some differential criteria that are commonly used to differentiate between them. These differential criteria include nutritional requirements and growth environment. L. Paracasei has been found to show specific differences with other Lactobacillus spp. in that it is somewhat heat resistant, grows well in ripening cheese, and it has high proteolytic activity.