The lactic acid bacteria are Gram-positive fermentative microorganisms known primarily for their roles as starter cultures and probiotics. The food industry represents one of the largest manufacturing industries in the world and recent trends are rapidly expanding the use of probiotic cultures within functional foods. Understanding and control of lactic acid bacteria is now being revolutionized by genomic sciences and the appearance of the complete genome sequences for Bifidobacterium longum, Lactobacillus johnsonii, Lactobacillus plantarum, and draft sequences for Lactobacillus gasseri and Lactobacillus casei. This explosion of DNA sequence information, accompanied by the development of bioinformatic tools for nucleic acid and protein analysis, now allows rapid characterization of the lactic acid bacteria for their genomic content and expression profiles across the entire genome. Comparative genomics has already revealed important similarities and differences in strains, species, and genera and will likely identify key genetic features responsible for the beneficial properties ascribed to probiotic lactic acid bacteria. Practical genomics for the lactic acid bacteria promises to establish the genetic landscape, correlate genotypes with desirable phenotypes, establish genetic criteria for strain selection, improve culture stability by stress preconditioning, provide opportunities for metabolic engineering, and uncover a mechanistic basis for the beneficial activities of probiotics when delivered in various foods. This presentation will examine the genomic content of probiotic Lactobacillus cultures, compared to those lactic acid bacterial genomes that have appeared recently. In addition, expression profiling by whole genome microarrays will be used to illustrate how environmental conditions encountered during biomanufacturing, fermentation, and the gastrointestinal tract can impact gene expression and culture functionality.

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The natural polysaccharide, kefiran (galactoglucan), was studied for the mechanism of its serum cholesterol lowering effect in 2 rat models one, loaded with cholesterol and another given orotic acid. Kefiran accelerated sterol excretion and protected hepatic injuries (GOT, GPT) in both models. In addition, histamine excretion decreased in the cecum content and feces, suggesting that kefiran may have various preventative functions.

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The effect of Escherichia coli K-12 on the transformation of hyocholic acid, α-muricholic acid, β-muricholic acid and 3α,7 β,12α-trihydroxy-5β-cholanoic acid was examined in aerobic and anaerobic cultures for 4 days and the activities were compared with those on cholic acid and chenodeoxycholic acid. Hyocholic acid was dehydrogenated, but to a lesser extent than cholic acid or chenodeoxycholic acid. However, α-muricholic acid, which has a 7α-hydroxyl group, was not dehydrogenated even after 4 days. This was confirmed by experiments using a cell-free crude enzyme preparation and by gas chromatographic analysis of bile acids in the medium culture. β-Muricholic acid and 3α,7β,12α-trihydroxy-5 β-cholanoic acid were not changed by Esherichia coli K-12.

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