I find B.subtilis to be a particularly interesting bacterium because it is a dominant bacterial workhorse in microbial fermentation and is used in foods, feeds, and industrial applications. A few examples include:

• Animal feeds as a probiotic
• Production of the soy-based traditional natto fermentation for human consumption
• As a probiotic for human consumption
• Large scale manufacturing of enzymes that are used in food, feed, leather, laundry, etc.
• Production of antibiotics, nucleotides, the vitamin riboflavin, the flavor agent ribose, and the supplement poly-γ-glutamic acid
• The genetics of B. subtilis has been widely studied and utilized that knowledge to manipulate the organism to make value added products.

I will limit my discussion to B.subtilis's application in animal feeds. B.subtilis is quite different from other microbial agents as it is a ubiquitous aerobic, or facultative aerobic, bacterium commonly recovered from water, soil, air, and decomposing plant residues. It produces endospores that are protected by a thick spore coat which enables them to withstand the high temperatures and acidic pH of the gut. This protective layer is not found in bifidobacterium, lactobacillus, etc., making them more vulnerable. These unique properties are extremely useful when applying B.subtilus in animal feeds.

The spores are typically formed when environmental conditions are not favorable (perhaps they learned how to survive during difficult times) and once favorable conditions return, the spores are germinated into vegetative cells. The spores are actually quite similar to plant seeds in that they are healthy but dormant until they are put into the right environmental conditions, when they start to germinate.

Major differences between the vegetative cells and spores:

Several studies have been conducted to understand the process of transforming spores to vegetative cells. Some studies clearly showed that the spores are germinating into vegetative cells within the host and providing beneficial effects.

Very recently the Lawrence Livermore National Laboratory have conducted a very interesting study and tracked as how spores break out of dormant state. This study was published in the June 2007 issue of the Proceedings of the National Academy of Sciences. For a quick look at the pictures please follow this link

Now let us examine as what are the most important attributes of a microorganism that can be potentially used as a probiotic in animal feeds.

• Microorganisms must be host specific
• Microorganisms must be viable (live) or in case of spores they should survive the gut environment and turn into vegetative cells
• Preferably shelf stable at room temperatures
• Microorganisms must have the ability to colonize within the intestinal tract of the animal of interest
• Safe to humans, animals and environment, Generally Recognized As Safe (GRAS)
• Ease of handling, long time storage and distribution
• Withstand higher temperatures during pelletization

The question is which one is better Spores or Live vegetative cells?

Comments (1)
Vijai Pasupuleti,   April 7th, 2008