Plant Archives

e-ISSN:2581-6063 (online), ISSN:0972-5210 Plant Archives Volume 21, No 1, 2021 pp. 1650-1654 DOI Url: https://doi.org/10.51470/PLANTARCHIVES.2021. v21.no1. 226 INTRODUCTION Probiotics are non-pathogenic microorganisms, which on ingested in adequate amount exert a positive health benefit on host (FAO/WHO, 2006). The search for more new probiotics is driven by the growing demand for probiotic functional food and beverages and dietary supplements due to rising levels of health consciousness and growing consumer awareness regarding gut health and the concept of preventive health care. It is now well established that some of the infections and disorders in the human body, such as irritable bowel syndrome, inflammatory bowel disease, and antibiotic-induced diarrhea, could be due to deficient or compromised intestinal microflora, and probiotics have been considered to be one of the disease control strategies to overcome such disorders (Dunne et al., 2001). Lactic acid bacteria (LAB) are most commonly studied probiotic for the past few decades. These are desirable microflora of thegastro intestinal tract (GIT) and are thus ‘generally regarded as safe’ (Tannock, 1997). Secondly, they are involved in the fermentation and are dominant microflora of fermented products. They are known to play an essential role in food preservation and inhibit spoilage microorganisms or food borne pathogens by production of lactic acid, acetic acid, H2O2, bacteriocin, diacetyl and CO2 (Nur and Aslim, 2010). Probiotic bacteria produce antimicrobial compounds whichmay exhibit either bactericidal or bacteriostatic properties (Pringsulaka et al., 2015). The probiotic microorganisms mainly consist of the strains of the genera Lactobacillus and Bifidobacterium,Streptococcus and some Enterococcus species (Morrow et al., 2012). The ability to survive and grow in low pH environment is characteristic for probiotics (Marteau et al., 1997). Bile tolerance of microorganisms has been used as a selective criterion for potential probiotics (De Smet et al., 1995). Bile resistance of some strains is related to specific enzyme activity-bile salt hydrolase (BSH) which helps hydrolyze conjugated bile, thus reducing its toxic effect (Du Toit et al., 1998). An important property of the probiotic strains is their antagonistic activity against pathogenic bacteria either by competitive exclusion, decrease of redox potential, interbacterial aggregation, or production of antimicrobial substances including organic acids, other inhibitory primary metabolites such as hydrogen peroxide, and special compounds like bacteriocins and antibiotics (Kalantzopoulos, 1997). Numerous clinical studies demonstrate that organisms of the Lactobacillus genus are both preventative and therapeutic in controlling intestinal infections when administered with milk containing these organisms (Gilliland, 1990). Antibiotic resistance of probiotic strains assures maintenance of healthy intestinal microbiota throughout antibiotic treatments of microbial infections. LAB display a wide range of antibiotic susceptibilities and resistances. In most cases, antibiotic resistance is not transmissible, but represents an intrinsic characteristic of the organism. An important requirement for probiotic strains is that they do not harbor mobile elements carrying resistance genes (Salminen et al., 1998). The objectives of this study were to characterize some Lactobacillus species, isolated from Egyptian raw milk according to the requirements for probiotics in order to consider their further application in the development of