Lactobacilli belong to the group of lactic acid bacteria (LAB), that have several distinguished abilities such as production of lactic acid, enzymes such as β-Galactosidase and natural antimicrobial substances called bacteriocins. Bacteriocin is a biopreservative agent potential of suppressing growth of some contaminant bacteria in food industry but its commercial availability is limited and costly. The study aimed to select isolates of Lactobacillus spp. potential for producing bacteriocins to suppress the growth of Escherichia coli ATCC 25922 and Bacillus subtilis NCIB3610, and to optimize the process of bacteriocin production. Results obtained in this study showed that L. acidophilus isolate CH1 was selected as the best candidate for bacteriocin among the four isolates that tested. The largest amounts of the bacteriocins were synthesized only in MRS medium was supplemented with K 2 HPO 4 (1.0%), Tween 80 (1%), Beef extract (1%), glucose, cyctein and peptone extract (1%). The optimization of culture conditions for bacteriocin production areas showed that corn steep liquor medium was the best medium for all isolates against Bacillus subtilis while no effect was observed on Escherichia coli ATCC 25922 except when used MRS medium. The optimum conditions for bacteriocin production were pH 6.0, temperature 34˚C with 4% Phenyl acetamide showing the greatest growth inhibition areas.

No abstract

Background Plant disease administration is difficult due to the soil-borne nature of the phytopathogens. Biological control of plant disease is a safe mode to avoid the problems related to fungal diseases that affect crops productivity. Results Twenty-three Trichoderma isolates were isolated from soil, surrounding healthy tomato roots from different regions in the Egyptian Governorate of Menoufia. Using a dual culture method to test the efficiency of Trichoderma isolates, the most effective isolate identified as Trichoderma atrovirde with percentage inhibition against Fusarium oxysporum f. sp. lycopersici (92.11%) and scanning electron microscope examination documented the mycoparasitic nature of T. atrovirde to F. oxysporum. Treatments with 10% filtrate T. atrovirde improved the growth aspects of tomato plants than the control plants or infected only, as well as the increase in phenol content (15.09 ug. g-1dry weight) and decreased disease incidence percentage (8%) than the plants infected only (60%). Conclusions This study clearly demonstrated that T. atrovirde had a significant inhibition against F. oxysporum. Greenhouse assays displayed the protective role of T. atrovirde inoculation directly against pathogen or indirectly related to the defense mechanism in the plant. So, this study recommends using T. atrovirde for biological control of wilt disease in tomato plants.

No abstract

No abstract