Abstract
The growth response of the biocontrol agent Pantoea agglomerans 2066-7 to change in water activity (aw), temperature, and pH was determined in vitro in basic medium. The minimum temperature at which 2066-7 was able to grow was 7°C, and the growth of 2066-7 did not change at varying pH levels (4–10.34). The best growth was obtained at a water activity of 0.98 in all media modified with the four solutes (glucose, glycerol, NaCl and polyethylene glycol). The solute used to reduce water activity had a great influence on bacterial growth, especially at unfavorable conditions (low temperature). This study has defined the range of environmental conditions (aw, pH, and temperature) over which the bacteria may be developed for biological control of plant diseases.
Highlights
The control of diseases in fruits and vegetables is still mainly based on the use of synthetic pesticides, the demand for produce free from chemical residues and the emergence of pesticides -resistant pathogen strains is constantly increasing
In this study we have modelled the growth rate of P. agglomerans according to temperature and aw, two major factors affecting bacteria growth
Teixido et al (2006) found that P. agglomerans was less tolerant of low aw in the presence of polyethylene glycol on medium, this difference of results may be due to the strain nature and isolation environment
Summary
The control of diseases in fruits and vegetables is still mainly based on the use of synthetic pesticides, the demand for produce free from chemical residues and the emergence of pesticides -resistant pathogen strains is constantly increasing. Following application on fruits and vegetables, biocontrol agents are exposed to a range of variable biotic and abiotic stress factors, such as competition, predation, changes in temperature, osmolarity, low pH, availability of nutrients and water. Water activity is a measure of the availability of water for biological functions and relates to water present in a food in “free” form. If the water activity is reduced drastically, microbial cells will lose viability, generally rapidly at first, and more slowly (Magan and Lacey, 1988; Plaza et al, 2003; mathlouthi, 2001). To assure a good application of biological control agent in the field and during storage a study of the optimal water activity, temperatures and pH of development of this agent is very important (Cañamás et al, 2009). The main objective of this work is to study the improvement of aw, temperature and pH tolerance observed in Pantoea agglomerans 2066-7
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