Lactobacillus Testing

The genus Lactobacillus is a group of gram-positive, rod shaped beneficial microorganisms of particular interest. They are strictly fermentative and anaerobic with complex nutrition requirements. They are a heterogeneous group of lactic acid bacteria and comprise the major part of this group. They have heterofermentative metabolism to produce lactic acid and obtain energy from the fermentation of glucose, lactose, and other sugars to lactate. Lactobacillus has more than 200 species and is characterized by its ability to produce lactic acid as a byproduct of glucose metabolism.

Figure 1. Electron micrograph of Lactobacillus and related foods

Lactobacillus is very critical in the production of fermented foods and thus of great economic importance. It is generally considered as a "good bacteria" and contributes to the good health. Lactobacillus is widely used to convert substrates of raw foods into fermented products such as yogurt, cheese, pickles, and wine. It can also be added into foods for the preservation purpose. Moreover, Lactobacillus is increasingly used in animal feed for antibiotic purpose. Bacteriocins produced by probiotics can have an inhibitory effect against pathogens. Lactobacillus is ubiquitous and can be found in substances rich in carbohydrates. It is very common in the bodies of animals and humans and represents a significant part of the intestinal. In healthy humans, the level of Lactobacillus in the colon is 10⁴ - 10⁸ CFU/g. The optimal growth temperature ranges from 30 to 40 ℃.

The probiotic effects of Lactobacillus have been studied and applied in food products. It is added into various foods as probiotic supplements to enhance the health of animals or humans through its beneficial functions on the microflora of gastrointestinal tract.

There are no reported cases of collective foodborne illnesses caused by the ingestion of foods containing Lactobacillus in healthy people. The probiotic effects of Lactobacillus in humans are dependent on the strain type and dose. According to the FAO/WHO statement, people can benefit from "live microorganisms" with a consumption of 10⁶ - 10¹⁰ viable cells per day. This dose can be fulfilled by consuming feed products or commercial probiotic foods mostly containing Lactobacillus. The detection of the level of live Lactobacillus in food products is important to know the probiotic effects of food samples.

Lactobacillus Testing of Food at Alfa Chemistry

The standard methods (EN/ISO and AOAC) that have been widely used to enumerate Lactobacillus are culture-based methods using general microbiological testing supplies. Selective mediums or Petrifilm dry rehydratable films are used to incubate Lactobacillus for 72 hours at 35 ℃. Then it is followed by the plate counting technique to determine the level of Lactobacillus in samples. Plating method for Lactobacillus uses solid medium such as MRS (De Man, Rogosa and Sharpe) agar. The medium used to differentiate Lactobacillus is based on their phenotype. The morphology of colonies on certain medium are taken for the presumptive identification. The confirmation test is performed using biochemical identification technique.

Alfa Chemistry offer accurate and validated testing platforms for the enumeration and confirmation of Lactobacillus in various food samples to meet customers' needs. We also have experience working on different standards and regulations.

Platform: Plate counting technique

Limit of detection: 10 CFU/g

Sample type: Solid and liquid food samples

Sample size: 25 g