Aims: The menace of antibiotic resistance has led to the search for alternatives, which in turn has diverted the attention to bacteriocins, antimicrobial peptides (AMPs) produced by bacteria for their bactericidal properties. The aim of our study was to isolate and partially purify bacteriocin from lactic acid bacteria (LAB) and comparing its antimicrobial activity with antibiotics. Methodology and results: Among 38 LAB screened using agar spot assay, LAB 28D1 showed the highest antimicrobial activity against the test bacterial strains. The proteinaceous nature of the antimicrobial compound extracted from LAB 28D1 was confirmed by its inactivation after treatment with proteolytic enzymes. The crude bacteriocin was found to be stable over a wide range of temperatures (60-100 °C) and pH (4-9). The bacteriocin was partially purified by ammonium sulfate precipitation (ASP) and the activity units were 204,800 AU/mL. The total protein and the specific activity of partially purified bacteriocin were found to be 24.585 mg and 124,954.24 AU/mg respectively. The molecular weight of partially purified bacteriocin was determined to be 8.5 kDa approximately. The efficacy of the partially purified bacteriocin against indicator bacterial strains was compared with antibiotics by the disc diffusion method and minimum inhibitory concentration (MIC). According to our study, the hospital waste isolate Enterococcus spp. was found to be multidrug-resistant (MDR) but sensitive to bacteriocin from LAB (MIC 0.06 ± 0 µg/mL). Conclusion, significance and impact of the study Bacteriocin from LAB has potential in combating MDR enterococcal infections.
Bacteriocins--isolation & ; purification ; Lactobacillales ; Drug Resistance, Microbial

Broad-spectrum of conventional antibiotics is one of the key factors that cause antibiotics-resistance of many bacteria. Bacteriocins are regarded as the next generation of antibiotics on account of their narrow-spectrum bactericidal activities. Many attentions have been paid to colicins because they are believed to be safe in regard to human body. In this paper, the genes encoding colicin S4 and its immunity protein were cloned into pQE30 to produce colicin S4 expression vector pQE30-Col S4. Colicin S4 was highly expressed as soluble form in gE colig M15 containing pQE30-Col S4. The yields ranged from 30 mg/L to 50 mg/L. The recombinant colicin S4 with an additional 6 His-tag at its N-terminus was found being similar to the natural colicin S4 in antibacterial activity. It only showed bactericidal activity against E. coli strains, thus makig it attractive to develop this protein as a novel antibiotic with narrow spectrum.
Anti-Bacterial Agents ; biosynthesis ; Bacteriocins ; biosynthesis ; genetics ; Cloning, Molecular ; Colicins ; biosynthesis ; genetics ; Escherichia coli ; drug effects ; genetics ; metabolism ; Recombinant Proteins ; biosynthesis ; genetics ; isolation & purification