BACTERIOCINS AND OTHER METABOLITES WITH BIOTECHNOLOGICAL POTENTIAL USES

Abstract

Over the course of history bacteria have proven to be microorganisms, with high potentials. Human has not been able yet to benefit or rather understand except a very sinall fraction of such potentials. Despite the fact that bacteria have been used for thousands of years in industry and food preservation processes. Recently, within the biotechnology revolution bacteria and other microorganisms attracted the interest as micro­ factories of active-compounds which are now used in many areas (Hunter-Cevera and Belt, 1999). Such field is in rapid growth and development, which has prompted many industries to change, trying to meet the requirements of the modern consumers who have awareness more than ever before.

Thus, the convergence between application and consumers has produced a new pattern in the methods of production and processing of agricultural products. As outcome, new era has begun with new expressions such as: bio-fertilization; bio-control; bio­ products, were agriculture products fertilized, protected, processed, and preserved by bacteria and some other microorganisms instead of chemicals.

In the food industry the consumers become increasingly aware of the relationship between diet and health. Thus, the demand for a balanced diet and functional food products that address specific health benefits is growing steadily. So, nowadays minimally processed foods of high quality, prepared without chemical preservatives, safe and possessing long shelf-life are preferred. Other benefits can be also provided to the consumers through the diet, such as adding probiotics strains which benefit its host and preserve the food in the same time. That needs researchers to provide strains with high potentials those can play such role in food.

Lactic acid bacteria (LAB), in particular, constitute the most appropriate choice for application as protective cultures, since they are present in all fermented foods, have a long history of safe use and form part of the gut microtlora of humans and animals. In addition, LAB produce a range of antimicrobial substances such as organic acids, hydrogen peroxide, bacteriocins, and bacteriocins-like compounds. which have been already used by the food industry (Allison and Klaenhammer. 1999; Cotter et al., 2005). Promising LAB strains or their metabolic products have been applied in food against pathogens, in dairy products such as soft and hard cheese, and meat products such as sausages and ham. Nowadays LAB consist the majority of the well known probiotics. To be considered as probiotics, bacteria should survive the gastrointestinal passage in order to be able to colonize the intestinal tract and become a part of the normal microbial tlora in the intestine. In addition, probiotics have to show some antagonistic activity against pathogens.

In previous study (Gomaa, 2005) it was shown how in vitro methods can be used for prediction of the survival potential of LAB in the human gastrointestinal tract. This is strongly linked to tolerance to pH 3 or lower, and to 0.3% bile acid or higher. Adhesion to Caco-2, antagonistic activity. production and technological characteristics, and antibiotic sensitivity are important probiotic properties as well. 15 of the 22 LAB strains in this study were originally isolated from feces of healthy one to six month old breast-fed infants