Enhancing the Probiotic Characteristics of Dairy Culture Bacteria

Linda F. Benedict, Aryana, Kayanush J.

Kayanush J. Aryana and Tanuja Muramalla

Probiotics are live microorganisms, which, when consumed in adequate amounts, confer a health benefit on the host. Probiotics were first commercialized via yogurts, namely “Yakult,” which was introduced in Japan in 1935. The Danone company introduced a yogurt product called “Activia” in France in 1987 and in the United States in 2006. The global probiotic products market has been steadily growing over the years and was estimated at $24.23 billion in 2011.

Some dairy cultures are known to provide health benefits. Lactobacillus bulgaricus produces a large amount of lactic acid, which completely inhibits the growth of Helicobacter pylori bacteria, known to cause peptic ulcers. It is also effective against the pathogen Salmonella typhimurium.

Streptococcus thermophilus has antioxidant activity that scavenges the body for free radicals and is effective in maintaining intestinal health.

Lactobacillus acidophilus provides several benefits, including:
• Reducing the incidence of diarrhea.
• Reducing toxic amine levels in blood of dialysis patients who have small bowel bacterial overgrowth.
• Producing lactase to digest lactose in lactose-intolerant subjects.
• Helping reduce serum cholesterol levels and risk for coronary heart disease.
• Helping recolonize the gastrointestinal tract after antibiotic therapy to aid digestion.
• Producing the bacteriocin CH5 that inhibits certain yeasts, molds and pathogenic bacteria.
• Improving bowel regularity.
• Benefiting the immune system.
• Decreasing the incidence of fever, cough and runny nose.
• Producing anti-inflammatory effects.
• Inhibiting breast cancer cell growth.
• Having positive effects on chemotherapy patients.
• Improving lipid metabolism.
• Producing vitamin K.

Characteristics of effective probiotics include being able to survive the passage through the digestive system, attach to the intestinal epithelia and colonize, maintain good viability, and use the nutrients and substances in a normal diet. These probiotics also are nonpathogenic and nontoxic; have a beneficial effect on a host; are stable during processing, storage and transportation; and are anti-inflammatory, immunostimulatory and antimutagenic.

A basic requirement for a bacterium to be an effective probiotic is the ability to survive stomach acid and bile in the gastrointestinal (GI) tract, move into the lower GI tract  “alive” and proliferate there, conferring the health benefits on the host. The question is whether these probiotic characteristics of acid tolerance and bile tolerance can be enhanced.

Low homogenization pressures and mild pulsed electric field conditions were studied to determine whether they can stimulate dairy culture bacteria to improve their probiotic characteristics of acid tolerance and bile tolerance. Under several mild homogenization pressures, Streptococcus thermophiles ST-M5, Lactobacillus delbrueckii ssp. bulgaricus LB-12 and Lactobacillus acidophilus LA-K were individually inoculated in cool, autoclaved skim milk and homogenized. Another set of experiments used mild pulsed electric field treatments – a technology used for nonthermal pasteurization.

Acid tolerance of the yogurt cultures LB-12 and ST-M5 was significantly improved by all of the low homogenization pressures studied. Homogenization pressures at the higher levels significantly improved the acid tolerance of LA-K. All mild homogenization pressures studied significantly improved bile tolerance of ST-M5 but not of LB-12, which was significantly decreased. Bile tolerance of LA-K was significantly improved only at one homogenization pressure.

Mild pulsed electric field treatments significantly improved the acid tolerance of LA-K and LB-12 but not of ST-M5.

Different bacteria sometimes exhibited a different response when subjected to the same low homogenization pressure or same mild pulsed electric field treatment. Depending upon the desired improvement in the characteristics of a culture bacterium, low homogenization pressure or mild pulsed electric field treatments could be used selectively. Pretreating cultures with some low homogenization pressures or mild pulsed electric fields can improve certain probiotic characteristics.

These results indicate that the probiotic characteristics – namely acid tolerance and bile tolerance – can be enhanced using certain processing conditions. It is a step toward providing consumers with probiotics that do not have to be taken in high initial doses as currently recommended.

Because bacteria typically do not like acidic (low pH) environments, improving the acid tolerance of health-beneficial culture bacteria also has implications in food safety where low pH can kill some pathogenic bacteria but preserve the health-beneficial bacteria with enhanced acid tolerance.

The next steps are to study if other dairy culture bacteria (such as Lactobacilli and Lactococci) also behave in the same manner or if they require different processes to enhance their probiotic characteristics.

Kayanush J. Aryana is a professor in the School of Animal Sciences and School of Nutrition and Food Sciences; Tanuja Muramalla is an instructor at the University of Hyderabad, India, and a former LSU graduate student.

(This article was published in the fall 2013 issue of Louisiana Agriculture magazine.)

12/5/2013 8:04:58 PM
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