Abstract
Three natural antibacterial compounds including bacteriocin like substance (BLS) produced from lactic acid bacteria (LAB), ethanolic extract of propolis (EEP), and nine plant extracts were evaluated against soft rot Bacillus strains. Testing in vivo these compounds were evaluated to control pear and apple soft rot disease. Among eight BLS tested, BLS of LAB2, LAB105 and LAB 107 exhibited the highest antibacterial activity as indicated by the formation of clear inhibition zone. Propolis extracts exhibited significant antibacterial activity against all tested soft rot Bacillus strains and it was noticed that the antibacterial activity was concentration dependent. Among nine plant extracts tested, extracts of Eucalyptus globulus and Psidium guajava exhibited the highest antibacterial activity. All tested antibacterial products significantly decreased apple and pear soft rot severity caused by Bacillus altitudinis compared to untreated control. The highest reduction percentage of soft rot severity was recorded for EEP followed by BLS from LAB and plant extracts tested, respectively. Combined pre-and post-harvest treatments of apple and pear with antimicrobial compounds proved to be more effective in reducing the soft rot severity and improved the physical and chemical properties of fruits during storage in both years of the study. The natural antimicrobial agents used in this study were promising compounds, since it seems to be more safe, economical and great potential for extending the shelf life and improve the quality of fruits. Therefore, the application of these compounds in the control of apple and pear soft rot could be advantageous for consumers, producers, and the environment.
Highlights
Bacterial soft rot was a destructive disease of fruits and vegetables worldwide and caused economic loss estimated between 15–30 percent of the harvested crop (Narayanasamy, 2006)
The main objectives of this study were (i) to evaluate in vitro antimicrobial activity of the bacteriocin like substance (BLS) produced by lactic acid bacteria, ethanolic extract of propolis (EEP) and some plant extracts against tested soft rot Bacillus strains, (ii) to compare the efficacy of pre, post– and combined pre– and post–harvest applications of these treatments for controlling soft rot disease of apple and pear fruits during storage and(iii) to determine changes in physical and chemical properties during storage of fruits treated with those natural products
The results of this study indicated that all tested natural antimicrobial compounds treatments could significantly reduce severity of soft rot disease caused with Bacillus altitudinis of apple and pear fruits stored for 60 days at 4oC compared to control treatments
Summary
Bacterial soft rot was a destructive disease of fruits and vegetables worldwide and caused economic loss estimated between 15–30 percent of the harvested crop (Narayanasamy, 2006). These substances can be defined as the compounds produced by living organisms with strong potential as sanitizing agents such as secondary metabolites from plants, bacteriocins, organic acids from bacteria, lysozyme from eggs and propolis from honey bee (Meyer et al, 2002; Kayser and Kolodziej, 1997). The main objectives of this study were (i) to evaluate in vitro antimicrobial activity of the bacteriocin like substance (BLS) produced by lactic acid bacteria, ethanolic extract of propolis (EEP) and some plant extracts against tested soft rot Bacillus strains, (ii) to compare the efficacy of pre–, post– and combined pre– and post–harvest applications of these treatments for controlling soft rot disease of apple and pear fruits during storage and(iii) to determine changes in physical and chemical properties during storage of fruits treated with those natural products. To eliminate the inhibitory effect of hydrogen peroxide, BLS was treated with catalase
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