L. acidophilus is a homofermentative, microaerophilic, short chain gram positive microorganism with rod morphology having its bacteriocins belonging to class II a. Several bacteriocins of L. acidophilus have been isolated and characterized. These are structurally similar, but their molecular weight varies as well as their spectrum of antimicrobial activity. They exhibit important technical properties, i.e., thermostability and retaining of activity at a wide pH range along with strong inhibitory actions against food spoilage and pathogenic bacteria make them an important class of biopreservatives. L. acidophilus can be added as an adjunct in many food fermentation processes contributing to unique taste, flavor, and texture. It also preserves the products by producing lactic acid and bacteriocins. A lot of new information regarding the bacteriocins of L. acidophilus has emerged during the last few years. In this review, an attempt has been made to summarize and discuss all the available information regarding the sources of bacteriocins production, their characteristics, and their antimicrobial action along with their application.

Enterococci are distinct lactic acid bacteria, and also natural inhabitants of human and animal intestinal tracts. They may enter food products during processing through direct or indirect contamination and are mostly present in fermented food products, such as cheese, sausages, olives, etc. Nowadays, they are extensively studied for the production of bacteriocins (enterocins), which prevent the growth of many food-borne and spoilage-causing pathogens, such as Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas spp., Bacillus spp. and Clostridium spp. Enterocins belong to class I, class IIa, class IIc, and class III of bacteriocins. Enterocins can be used in different food products in order to enhance their shelf life because they are heat stable and show activity over wide pH range. Enterocins are effective as well as safe to be used in the food system because they are "generally recognized as safe" (GRAS). Enterococcus faecium and Enterococcus faecalis are the predominant bacteriocin-producing species of Enterococcus in food products. The following review is focused on the bacteriocin-producing strains of Enterococcus faecium isolated from different traditional fermented food products.The aim of this review is to cover general features of the enterocins of Enterococcus faecium, the attempts made to purify them, and their potential application in different food products to improve their overall safety.

The perishable nature of milk is the main problem for collection of raw milk in developing countries, especially during summer season. In this study, naturally occurring lactoperoxidase system of raw buffalo's milk was stabilized by equal proportions of 10, 20 and 30 ppm of hydrogen peroxide (H2O2) and sodium thiocyanate (NaSCN) immediately after collection. The results of the quality control tests (i.e., total viable counts, titratable acidity, pH and milk stability) indicated that milk stabilized with 10, 20 and 30 ppm of H2O2 and NaSCN, stored at 40C, significantly (P < 0.05) increased the shelf life of raw milk up to 8 and 16 h as compared with control, which curdled within 6 h of milking. Later on, these stabilized milk samples were assessed for the preparation of yogurt by using a mixed culture of Streptococcus thermophilus and Lactobacillus bulgaricus. A significant (P < 0.05) reduction of lactic acid production was observed and the proportions of H2O2/NaSCN increased compared with control. This effectiveness was more pronounced with 20 and 30 ppm as compared with 10 ppm. The results of organoleptic evaluation showed that yogurt prepared from 10 ppm stabilized milk got the highest score. PRACTICAL APPLICATIONS This study reveals a significant effect of lactoperoxidase system on preserving raw buffalo's milk for more than 16 h at 40C as compared with control. Therefore, this system provides an opportunity for the collection of raw milk from wildly scattered remote areas where no proper transportation and chilling units are available. This system also seems to be useful for the collection of evening milk. However, both higher concentrations of hydrogen peroxide (H2O2) and sodium thiocyanate (NaSCN) showed deteriorative effects on yogurt starter culture activity for yogurt making. Only 10 ppm concentration proved to be suitable for yogurt preparation. Thus, it was concluded that minimum level of H2O2/NaSCN concentration is required for cultural activity in product development procedures.

Antimicrobial activity of 79 strains of Lactobacillus isolated from indigenous dahi were tested against the indicator strains of food pathogens (Escherichia coli, Streptococcus faecalis, Staphylococcus aureus, Salmonella typhi). Among these only eleven isolates produced inhibition zones of variable size against indicator microorganisms. Later on, only one strain of Lactobacillus acidophilus (TS1) was found to produce a wider zone of inhibition against all indicator microorganisms. The antimicrobial activity of this strain was inactivated by the proteolytic enzyme proteinase K and trypsin but not by α-amylase and lipase thus confirming its proteinaceous nature. It also showed a wide range of thermostability from 70-121 °C for 15 min and retained their antimicrobial activity over a wide range of pH (3-10). The addition of bacteriocin to the earlier growth phase showed pronounced inhibition against E. coli, and Streptococcus faecalis, as compared to Staphylococcus aureus, and Salmonella typhi. The molecular weight of the substance was in the range of 7.5 kDa. This result suggested that bacteriocin might be useful as a biopreservative in different food commodities.

Diversity and density of lactic acid bacteria from indigenous dahi were studied by the determination of morphological, cultural, physiological and biochemical characteristics. A total of 143 isolates were identified phenotypically and divided into three genera: Lactobacillus, Lactococcus and Streptococcus. The microorganisms isolated were Lactobacillus bulgaricus (23.77%), Streptococcus thermophilus (26.57%), Lactococcus lactis (13.9%), Lactobacillus acidophilus (9.79%), Lactobacillus lactis (9.79%), Lactobacillus delbreuckii (4.89%), Lactobacillus helveticus (2.79%), Lactobacillus casei (1.39%), Lactobacillus casei ssp. psuedoplantarum (2.79%), Streptococcus cremoris (2.09%) and Streptococcus lactis sub. diacetylactis (2.09%).