Encapsulation of beneficial probiotic bacteria in extracellular matrix from biofilm-forming Bacillus subtilis.

Probiotics, live microbial supplements, are often incorporated into foods and beverages to provide putative health benefits. To ensure their beneficial effects, these organisms must survive processing and storage of food, its passage through the upper gastrointestinal tract (GIT), and subsequent chemical ingestion processes until they reach their target organ. However, there is considerable loss of viability of probiotic bacteria in the acidic conditions of the stomach and the high bile concentration in the small intestine. Bacillus subtilis, a spore-forming non-pathogenic bacterium, recently has gained interest in its probiotic properties; it can effectively maintain a favorable balance of microflora in the GIT. In addition, B. subtilis produces an extracellular matrix that protects it from stressful environments. We suggested that the extracellular matrix produced by B. subtilis could protect other probiotic bacteria and therefore potentially could be used as a vehicle for delivering viable probiotic cells to humans. Therefore, we developed a novel cultivation system that enables co-culturing of B. subtilis along with probiotic lactic acid bacteria (LAB) by increasing production of the extracellular matrix by B. subtilis cells. Moreover, we showed that B. subtilis improved survivability of LAB during food preparation, storage and ingestion. Therefore, we believe that the results of our study will provide a novel technique of using a natural system for preservation and delivery of probiotics to humans.

An in vivo metabolic approach for deciphering the product specificity of glycerate kinase proves that both E. coli's glycerate kinases generate 2-phosphoglycerate.

Apart from addressing humanity's growing demand for fuels, pharmaceuticals, plastics and other value added chemicals, metabolic engineering of microbes can serve as a powerful tool to address questions concerning the characteristics of cellular metabolism. Along these lines, we developed an in vivo metabolic strategy that conclusively identifies the product specificity of glycerate kinase. By deleting E. coli's phosphoglycerate mutases, we divide its central metabolism into an 'upper' and 'lower' metabolism, each requiring its own carbon source for the bacterium to grow. Glycerate can serve to replace the upper or lower carbon source depending on the product of glycerate kinase. Using this strategy we show that while glycerate kinase from Arabidopsis thaliana produces 3-phosphoglycerate, both E. coli's enzymes generate 2-phosphoglycerate. This strategy represents a general approach to decipher enzyme specificity under physiological conditions.