Abstract
Production of anti-microbial substances by Lactobacillus plantarum , immobilized in calcium alginate gel beads was investigated. The beads were very unstable in De man Rogosa and Sharpe (MRS) medium but the stability of the beads improved by removing potassium and phosphate from the MRS medium. The highest stability of the beads was achieved by addition of calcium chloride to the medium. When 5% calcium chloride was added to the medium, the stability of the beads increased from 24h (when no calcium chloride was added) to 500 h, without adverse effects on the growth and antimicrobial substance production by the immobilized cells. Although the produced antimicrobial substances inhibited the growth of Bacillus cereus, B. subtilis, Listeria monocytogenes, and Escherichia coli, B. subtilis was the most susceptible. Under all the conditions investigated, immobilization of L. plantarum significantly increased the organism’s ability to produce antimicrobial substances. Although suspended cells produced higher antimicrobial substances under anaerobic condition, aerobic condition improved antimicrobial substance production by the immobilized cells. This implies that microaerophilic condition is the best for antimicrobial substance production by L. plantarum . Keywords: Bio-insecticide, anti-microbial substances, Bacillus thuringiensis , endotoxin
Highlights
Lactic acid bacteria (LAB) are the most prominent nonpathogenic bacteria that play vital roles in everyday life ranging from fermentation, preservation and production of wholesome food and vitamins (Udhayashere et al, 2012)
Bacteriocins are produced by a broad spectrum of bacteria, those produced by LAB are of particular interest in food industry because these bacteria have generally been recognized as safe (GRAS) organism (Nettles and Barefoot, 1993)
This work was designed to improve the production of antimicrobial substances by lactic acid bacteria immobilized in caalginate gel beads and to analyze their inhibitory activities against food spoilage and pathogenic microorganisms
Summary
Lactic acid bacteria (LAB) are the most prominent nonpathogenic bacteria that play vital roles in everyday life ranging from fermentation, preservation and production of wholesome food and vitamins (Udhayashere et al, 2012). They have been used in food bio-preservation because of their antimicrobial metabolites. Bacteriocins are antimicrobial peptides or small protein complex displaying bactericidal activity against food spoilage and food pathogenic organisms. Bacteriocin are ribosomally synthesized peptides produced by various bacteria and exhibit a bacteriostatic or bacteriocidal activity against bacteria that are genetically close relatives (Savadogo et al, 2006; Yang et al, 2014).
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