In the recent past, a number of probiotic strains have been screened and selected for incorporation into commercial functional food products. Some of these strains have been validated for specific health benefits through human clinical trials others have been documented as offering potential health benefits. In the past commercial probiotic strains were selected for their technological properties, however, in the recent past, validated health benefits have assumed much greater importance. This review includes the characteristics of genus Bifidobacteriaand Lactobacillus and other microbes that are currently considered as probiotic organisms, selection criteria

employed to screen them as effective probiotic strains, their validated and potential health benefits documented. In the recent screening and selection of strains for probiotic efficacy a change in focus from having technological properties to offering validated health benefits may allow the strains to lose their technological properties including the ability to survive both food processing and gastrointestinal environment. Further, different food matrices may have different interactions with probiotic bacterial cells and hence validated human health benefits cannot be generalised for all food matrices as vehicles for administration and delivery.

Chitosan-coated alginate-starch (CCAS) capsules containing approximately 108 CFU of Lactobacillus casei Shirota strain cells (LCS) were fed to mice and the release profile of bacteria from CCAS capsules in murine GI tract was investigated at different time intervals. There was a complete release (108 CFU) of LCS from capsules within 12 h in mice ileal region. There was only a partial release of encapsulated LCS, in duodenal, jejunal and colon regions, while there was no release of encapsulated LCS in stomach from the CCAS capsules even after 24 h. The effect of feeding (14 days) CCAS encapsulated LCS on faecal microbial population and immune parameters in mice were also determined. The numbers of LCS recovered from the faeces confirmed adequate percentage of LCS survived passage through gastrointestinal tract. A concomitant increase in the LCS and total lactobacilli count during the test period was observed in the group fed with CCAS encapsulated bacteria compared to the one fed with free non-encapsulated bacteria. This experiment also showed that the CCAS microencapsulated LCS did not affect or mask the probiotic bacteria’s immunomodulatory activity. The effect on the specific immune response was assessed by measuring cytokine production of the mouse splenocytes. There was significant increase (p<0.05) in interleukin (IL-10) and interferon (IFN)-γ production between groups fed with CCAS encapsulated LCS and free LCS compared to the control and the one fed

with empty CCAS alginate capsules. Chitosan coated alginate-starch capsules

can be effectively used to deliver viable bacteria safely to animal intestine for

increased immunomodulatory activity.

The viability of microencapsulated Lactobacillus acidophilus LA1 beads containing different levels of fructo-oligo-saccharides (FOS - 1.5%, 2.5% and 3%) and partially hydrolysed guar gum (PHGG - 3% and 5%) were studied under different conditions of pH (1.0, 2.0), bile salt concentrations (1%, 1.5% and 2%) and high temperature exposure (75° and 85° C). The microcapsules had 8-9 log of viable cells of L. acidophilus LA1. Cells entrapped in alginate beads with no prebiotic (CAB) and containing prebiotic (PAB) were incubated at 37°C under the test conditions of pH, bile and temperature for different lengths of time. Survival rates decreased with increasing incubation periods at the experimental levels of pH, bile concentrations and severity of heat. PAB survived significantly better than CAB at higher levels of the prebiotic concentrations. The matrix with 3% PHGG, 3% alginate, and 2%

starch performed well at all test conditions.

Probiotics are live microorganisms which transit the gastrointestinal tract and in

doing so benefit the health of the consumer. Therapeutic benefits have led to an

increase in the incorporation of probiotic bacteria such as lactobacilli and

bifidobacteria in dairy products, especially yoghurts. Microencapsulation enhanced the survival of probiotic cultures compared to free cells in yogurts stored for a longer periods. It also protects the bacteria from harsh conditions (low pH, antibiotics, bacteriocins, bile salt concentration etc).  Microencapsulation of various bacterial cultures including probiotics has been a common practice for extending their storage life and converting them into a powder form for ease of their use.

Probiotic bacteria (Lactobacillus acidophilus LAFTI L10 and Bifidobacterium lactis LAFTI B94) were encapsulated in calcium-alginate hydro-gel to study the effect of encapsulation on their survival in Cheddar cheese. Twelve batches of Cheddar cheese were manufactured incorporating encapsulated and free probiotic bacteria. The survival and the effect of encapsulated probiotic bacteria on the growth of starter lactic acid bacteria (SLAB) and non-starter lactic acid bacteria (NSLAB) were assessed over a six-month ripening period. The survival of encapsulated bacteria (107 cfu/g) was found to be significantly (P<0.05) greater than that of free bacteria (105 cfu/g) at the end of six-months. Also, addition of encapsulated probiotic bacteria did not change the population of SLAB and NSLAB. This study therefore

demonstrates that encapsulated probiotic bacteria survive better than free probiotic bacteria in Cheddar cheese during the long ripening period and had no effect on the SLAB and NSLAB growth during ripening.

The effects of Lactobacillus acidophilus LAFTI L10 on gene expression in the

small intestine of mice was evaluated using microarrays. Male BALB/c mice were orally fed with 108 colony forming units of L. acidophilus in skimmed milk powder for 14 days. Control mice received skimmed milk powder without L. acidophilus. After 14 days, distal end of the small intestine was excised for microarray analysis of gene expression. L. acidophilus-fed mice altered the expression of genes such as CD40 ligand, CD200 receptor-3 and trefoil factor 2, which are involved in host defence mechanisms. Overall, the expression of functional genes influenced by L. acidophilus in the small intestine of mice offer as a basis for further investigation into its probiotic effects.